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Background: Equine asthma is a common, non-infectious, chronic lung disease that affects up to 80% of the horse population. Strict phenotyping and identification of subclinically asthmatic horses can be challenging. The aim of this study was to describe equine asthma phenotypes (mild, moderate, and severe asthma) defined by BALF cytology and occurrence of clinical signs in a population of privately owned horses and to identify the variables and examination steps with best discriminative potential. The standardised examination protocol included clinical examinations, blood work, airway endoscopy with bronchoalveolar lavage fluid analysis, arterial blood gas analysis and radiography under clinical conditions performed by one veterinarian. Results: Out of 26 horses, four were diagnosed with mild (subclinical), seven with moderate, and seven with severe asthma based on clinical examination and BALF cytology. Eight horses served as controls. Cough with history of coughing was the strongest variable in phenotype differentiation. Factor analysis revealed an increasing clinical variability with disease severity and an overlapping of clinical presentations between phenotypes. Elevated mast cell (4/4 horses) and neutrophil counts (3/4 horses) in bronchoalveolar lavage cytology differentiated mild asthmatic horses from healthy horses. Moderate and severe asthmatic horses were characterised by clinical signs and neutrophil counts. Conclusions: The results indicate that medical history, clinical examination and bronchoalveolar lavage cytology are minimum indispensable steps to diagnose equine asthma and that phenotypes are clinically overlapping. A differentiation of three phenotypes without neutrophil and mast cell counts in bronchoalveolar lavage cytology is not sufficient for clinical diagnostics. A comparably exact diagnosis cannot be achieved by relying on alternative examinations used in this study. Screenings of inconspicuous horses with bronchoalveolar lavage can aid in diagnosing subclinically affected animals, however, group size was small, the procedure is invasive and clinical relevance of slightly elevated cells in bronchoalveolar lavage remains unclear. Clinical relevance could not be clarified in this study, since follow-up examinations or lung function testing were not performed. [ABSTRACT FROM AUTHOR]

Simple Summary: To ensure adequate immune protection, foals are dependent on a sufficient intake of good quality colostrum shortly after birth. In this study we analyzed whether a supplemented Saccharomyces cerevisiae fermentation product (SCFP) to mares in late gestation alters the biological activity of their colostrum and whether the uptake of such a colostrum affects the immediate response to vaccination at the age of 5 to 8 months. Twenty-six pregnant mares were randomly assigned to receive either a supplement or no supplementation twelve weeks before the calculated date of birth. Mares were actively vaccinated three weeks before parturition with a commercial influenza and tetanus vaccine. Their foals were actively vaccinated against equine influenza and tetanus after weaning. Blood cell composition was determined directly before vaccination and 24 h later. The biological activity of colostrum samples was assessed in a cell viability assay with an intestinal epithelial cell line. Colostrum from SCFP-fed mares exhibited significantly higher growth-promoting activity compared to control mares. While SCFP feeding did not affect the early vaccination response of mares, the biological activity of colostrum had a significant effect on vaccine-induced changes in blood composition of weanling foals. Therefore, a Saccharomyces cerevisiae fermentation product supplement may improve the biological activity of colostrum, which affects innate immune responses of foals. The quality of equine colostrum is typically defined by refractometry or the concentration of maternal antibodies. However, the activity of other equine colostral bioactive molecules has not yet been investigated. This study analyzed whether the administration of a Saccharomyces cerevisiae fermentation product (SCFP) influences the biological activity of mare colostrum and whether the biological activity of colostrum has a lasting immunomodulating effect for foals. A total of fourteen pregnant mares received 20 g/day of a SCFP for a period of twelve weeks prior to the calculated date of birth (SCFP-group). Twelve pregnant mares without supplementation served as controls (CON). Colostral Brix values were determined within three hours after parturition. The concentration of IgG in blood sera and colostrum samples was determined with an ELISA. The biological activity was determined in a cell growth assay with a porcine epithelial cell line (IPEC-J2). Mares (at three weeks before the calculated date of birth) and foals (at the age of 5–8 months) received a parenteral active vaccination against influenza and tetanus. The administration of SCFP did not alter the mare's serum and colostrum IgG concentrations and did not exert a significant influence on the mares' early response to the vaccination. Growth and diarrhea episodes were comparable between foals of supplemented mares (SCFP) and foals of mares without supplementation (CON). Colostrum samples from SCFP-supplemented mares exhibited heightened biological activity. While SFCP and CON foals did not differ in their early response to vaccination, the vaccination-induced alterations in circulating neutrophilic granulocyte numbers were significantly correlated with the biological colostrum activity. These findings suggest that the supplementation of mares in late gestation with SCFP can enhance the biological activity of colostrum, which subsequently influences the innate immune responses of their offspring in later life. [ABSTRACT FROM AUTHOR]

Simple Summary: Getah virus (GETV) is an important zoonotic pathogen with an extensive host range, including horses, pigs, cattle, sheep, birds, and humans, resulting in substantial losses in the livestock and agricultural industries; as such, the prevalence and impact of GETV are significant concerns in China. In this study, the antigen domain of the E2 glycoprotein of GETV was expressed and purified in the Escherichia coli expression system, and an on-site immunochromatographic strip (ICS) was successfully developed to detect GETV antibodies in horses. The ICS has the advantages of being rapid, sensitive, specific, and is an effective method for the detection of GETV in horses that does not rely on special equipment or skilled personnel and can be used for the field diagnosis of GETV in horses. The prevalence and impact of Getah virus (GETV) are significant concerns in China. GETV can infect a wide range of animals, including horses, pigs, sheep, cattle, birds, and humans, resulting in substantial losses in the livestock and agricultural industries. GETV infection can cause the development of ulcers and inflammation in the mouth and gums of horses, which result in pain and discomfort and lead to symptoms such as reduced appetite, drooling, and difficulty chewing. As a result, there is a pressing need for efficient and rapid disease diagnosis methods. However, the currently available diagnostic methods have limitations in terms of operational time, equipment, and the experience of the individuals using them. In this study, a rapid, specific, and sensitive detection method was developed using a colloidal gold-based immunochromatographic strip (ICS) for the detection of antibodies against GETV in horses. To prepare the ICS, the antigen domain of the E2 glycoprotein of GETV was expressed using the Escherichia coli expression system after analysis with DNAstar v7.1 software. The nitrocellulose membrane was coated with rE2 protein or SPA to form the test line and control line, respectively. After optimizing the reaction conditions, the sensitivity, specificity, and repeatability of the strip were verified. The results showed that the test strip had a detection limit of up to 1:320 dilutions for GETV-positive serum, with no cross-reactivity observed with other equine-susceptible pathogens such as equine arteritis virus (EAV), equine herpesvirus-1 (EHV-I), equine infectious anemia virus (EIAV), equine influenza virus (EIV), African horse sickness virus (AHSV), and Japanese encephalitis virus (JEV). Furthermore, the ICS exhibited a concordance rate of 94.0% when testing 182 clinical serum samples compared to the virus neutralization test. Overall, this ICS diagnosis method will be an effective tool for the rapid detection of GETV in the field. [ABSTRACT FROM AUTHOR]

Equid alphaherpesvirus 1 (EHV-1) is a ubiquitous and significant viral pathogen in horses worldwide, causing a range of conditions, including fever, respiratory disease, abortion in pregnant mares and the severe neurological disease called equine herpes myeloencephalopathy (EHM). Despite that EHV-1 is a notifiable animal disease in Sweden, there is limited knowledge about the circulating strains. This study aimed to analyze the genetic diversity of EHV-1 strains in equine samples from different Swedish outbreaks by partial genome sequencing. Genotyping based on three selected open reading frames ORF11, ORF30, and ORF34 in the viral genome was conducted for 55 outbreaks of EHV-1 spanning from the years 2012 to 2021. The analysis revealed 14 different genovariants, with one prominent genovariant identified in 49% of the outbreaks. Additionally, the study identified seven mutations not previously described. Three new mutations were demonstrated in ORF11, all synonymous, and four new mutations in ORF34, two synonymous, and two non-synonymous. Notably, different EHV-1 genovariants were found in five out of six studied EHM outbreaks, but clonal spreading was shown within the outbreaks. Moreover, the study demonstrated that healthy (recovered) horses that returned from an EHM outbreak at an international meeting in Valencia, Spain (2021), were positive for the virus clone responsible for the severe disease outbreak despite several weeks of quarantine. These findings shed light on the genetic diversity and transmission dynamics of the virus and significantly contribute to better understanding of the epidemiology of EHV-1 in Sweden and globally. [ABSTRACT FROM AUTHOR]

Equine influenza (EI) is a severe infectious disease that causes huge economic losses to the horse industry. Spatial epidemiology technology can explore the spatiotemporal distribution characteristics and occurrence risks of infectious diseases, it has played an important role in the prevention and control of major infectious diseases in humans and animals. For the first time, this study conducted a systematic analysis of the spatiotemporal distribution of EI using SaTScan software and investigated the important environmental variables and suitable areas for EI occurrence using the Maxent model. A total of 517 occurrences of EI from 2005 to 2022 were evaluated, and 14 significant spatiotemporal clusters were identified. Furthermore, a Maxent model was successfully established with high prediction accuracy (AUC = 0.920 ± 0.008). The results indicated that annual average ultraviolet radiation, horse density, and precipitation of the coldest quarter were the three most important environmental variables affecting EI occurrence. The suitable areas for EI occurrence are widely distributed across all continents, especially in Asia (India, Mongolia, and China) and the Americas (Brazil, Uruguay, USA, and Mexico). In the future, these suitable areas will expand and move eastward. The largest expansion is predicted under SSP126 scenarios, while the opposite trend will be observed under SSP585 scenarios. This study presents the spatial epidemiological characteristics of EI for the first time. The results could provide valuable scientific insights that can effectively inform prevention and control strategies in regions at risk of EI worldwide. [ABSTRACT FROM AUTHOR]

Equine influenza is a viral disease caused by the equine influenza virus (EIV), and according to the WOAH, it is mandatory to report these infections. In Latin America and Colombia, EIV risk factors have not been analyzed. The objective of this research is to perform an epidemiological and molecular analysis of the EIV in horses with respiratory symptoms from 2020 to 2023 in Colombia. Molecular EIV detection was performed using RT–qPCR and nanopore sequencing. A risk analysis was also performed via the GEE method. A total of 188 equines with EIV respiratory symptoms were recruited. The positivity rate was 33.5%. The descriptive analysis showed that only 12.8% of the horses were vaccinated, and measures such as the quarantine and isolation of symptomatic animals accounted for 91.5% and 88.8%, respectively. The variables associated with the EIV were the non-isolation of positive individuals (OR = 8.16, 95% CI (1.52–43.67), p = 0.014) and sharing space with poultry (OR = 2.16, 95% CI (1.09–4.26), p = 0.027). In conclusion, this is the first EIV investigation in symptomatic horses in Colombia, highlighting the presence of the virus in the country and the need to improve preventive and control measures. [ABSTRACT FROM AUTHOR]

OBJECTIVE To investigate the role of equine herpesvirus-2 (EHV-2) and equine herpesvirus-5 (EHV-5) in equine glandular gastric disease (EGGD) by visualizing and quantifying these gamma herpesviruses in EGGD-affected and normal glandular gastric mucosa of horses. A secondary objective was to describe the histopathological abnormalities in the equine gastric glandular mucosa in horses with EGGD. ANIMALS 29 horses (n = 21 postmortem and 8 gastroscopy) categorized as normal (11), EGGD (12), or both EGGD and equine squamous gastric disease (6). METHODS Glandular gastric mucosal samples were collected from horses by gastroscopy or postmortem. Histopathology and in situ hybridization targeting EHV-2 and EHV-5 were performed on grossly normal and abnormal glandular gastric mucosa. The number of in situ hybridization-positive cells per millimeter squared of tissue was calculated. Evaluators were blinded to groups. RESULTS Glandular gastric tissues from horses without EGGD had higher viral loads in the mucosa than normal or abnormal tissues from EGGD horses. There was no difference in viral loads for EHV-2 or EHV-5 between grossly or endoscopically normal to abnormal gastric tissues within horses with EGGD. Lymphocytic plasmacytic gastritis was the most common histopathological abnormality, with only 3 horses having mucosal disruption (glandular ulcer or erosion). CLINICAL RELEVANCE Equine gamma herpesviruses are unlikely to play a role in the pathophysiology of EGGD. EGGD is frequently inflammatory with occasional mucosal disruption (ulcer or erosion). [ABSTRACT FROM AUTHOR]

Equine herpesvirus type 1 (EHV-1) is a contagious respiratory pathogen that infects the mucosa of the upper respiratory tract (URT). Mucosal immune responses at the URT provide the first line of defense against EHV-1 and are crucial for orchestrating immunity. To define host-pathogen interactions, we characterized B-cell responses, antibody isotype functions, and EHV-1 replication of susceptible (non-immune) and clinically protected (immune) horses after experimental EHV-1 infection. Nasal secretion and nasal wash samples were collected and used for the isolation of DNA, RNA, and mucosal antibodies. Shedding of infectious virus, EHV-1 copy numbers, viral RNA expression, and host B-cell activation in the URT were compared based on host immune status. Mucosal EHV-1-specific antibody responses were associated with EHV-1 shedding and viral RNA transcription. Finally, mucosal immunoglobulin G (IgG) and IgA isotypes were purified and tested for neutralizing capabilities. IgG1 and IgG4/7 neutralized EHV-1, while IgG3/5, IgG6, and IgA did not. Immune horses secreted high amounts of mucosal EHV-1-specific IgG4/7 antibodies and quickly upregulated B-cell pathway genes, while EHV-1 was undetected by virus isolation and PCR. RNA transcription analysis reinforced incomplete viral replication in immune horses. In contrast, complete viral replication with high viral copy numbers and shedding of infectious viruses was characteristic for non-immune horses, together with low or absent EHV-1-specific neutralizing antibodies during viral replication. These data confirm that pre-existing mucosal IgG1 and IgG4/7 and rapid B-cell activation upon EHV-1 infection are essential for virus neutralization, regulation of viral replication, and mucosal immunity against EHV-1. IMPORTANCE Equine herpesvirus type 1 (EHV-1) causes respiratory disease, abortion storms, and neurologic outbreaks known as equine herpes myeloencephalopathy (EHM). EHV-1 is transmitted with respiratory secretions by nose-to-nose contact or via fomites. The virus initially infects the epithelium of the upper respiratory tract (URT). Host-pathogen interactions and mucosal immunity at the viral entry site provide the first line of defense against the EHV-1. Robust mucosal immunity can be essential in protecting against EHV-1 and to reduce EHM outbreaks. It has previously been shown that immune horses do not establish cell-associated viremia, the prerequisite for EHM. Here, we demonstrate how mucosal antibodies can prevent the replication of EHV-1 at the epithelium of the URT and, thereby, the progression of the virus to the peripheral blood. The findings improve the mechanistic understanding of mucosal immunity against EHV-1 and can support the development of enhanced diagnostic tools, vaccines against EHM, and the management of EHV-1 outbreaks. [ABSTRACT FROM AUTHOR]

Introduction: The Nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway has been extensively studied for its role in regulating antioxidant and antiviral responses. The Equid herpesvirus type 8 (EqHV-8) poses a significant threat to the equine industry, primarily manifesting as respiratory disease, abortions, and neurological disorders in horses and donkeys. Oxidative stress is considered a key factor associated with pathogenesis of EqHV-8 infection. Unfortunately, there is currently a dearth of therapeutic interventions available for the effective control of EqHV-8. Rutin has been well documented for its antioxidant and antiviral potential. In current study we focused on the evaluation of Rutin as a potential therapeutic agent against EqHV-8 infection. Methods: For this purpose,we encompassed both in-vitro and in-vivo investigations to assess the effectiveness of Rutin in combatting EqHV-8 infection. Results and Discussion: The results obtained from in vitro experiments demonstrated that Rutin exerted a pronounced inhibitory effect on EqHV-8 at multiple stages of the viral life cycle. Through meticulous experimentation, we elucidated that Rutin's antiviral action against EqHV-8 is intricately linked to the Nrf2/HO-1 signaling pathway-mediated antioxidant response. Activation of this pathway by Rutin was found to significantly impede EqHV-8 replication, thereby diminishing the viral load. This mechanistic insight not only enhances our understanding of the antiviral potential of Rutin but also highlights the significance of antioxidant stress responses in combating EqHV-8 infection. To complement our in vitro findings, we conducted in vivo studies employing a mouse model. These experiments revealed that Rutin administration resulted in a substantial reduction in EqHV-8 infection within the lungs of the mice, underscoring the compound's therapeutic promise in vivo. Conclusion: In summation, our finding showed that Rutin holds promise as a novel and effective therapeutic agent for the prevention and control of EqHV-8 infections. [ABSTRACT FROM AUTHOR]

Abstract Equine influenza virus (EIV) remains a threat to horses, despite the availability of vaccines. Strategies to monitor the virus and prevent potential vaccine failure revolve around serological assays, RT-qPCR amplification, and sequencing the viral hemagglutinin (HA) and neuraminidase (NA) genes. These approaches overlook the contribution of other viral proteins in driving virulence. This study assesses the potential of long-read nanopore sequencing for fast and precise sequencing of circulating equine influenza viruses. Therefore, two French Florida Clade 1 strains, including the one circulating in winter 2018–2019 exhibiting more pronounced pathogenicity than usual, as well as the two currently OIE-recommended vaccine strains, were sequenced. Our results demonstrated the reliability of this sequencing method in generating accurate sequences. Sequence analysis of HA revealed a subtle antigenic drift in the French EIV strains, with specific substitutions, such as T163I in A/equine/Paris/1/2018 and the N188T mutation in post-2015 strains; both substitutions were in antigenic site B. Antigenic site E exhibited modifications in post-2018 strains, with the N63D substitution. Segment 2 sequencing also revealed that the A/equine/Paris/1/2018 strain encodes a longer variant of the PB1-F2 protein when compared to other Florida clade 1 strains (90 amino acids long versus 81 amino acids long). Further biological and biochemistry assays demonstrated that this PB1-F2 variant has enhanced abilities to abolish the mitochondrial membrane potential ΔΨm and permeabilize synthetic membranes. Altogether, our results highlight the interest in rapidly characterizing the complete genome of circulating strains with next-generation sequencing technologies to adapt vaccines and identify specific virulence markers of EIV.

Background: The equine gastrointestinal (GI) microbiome has been described in the context of various diseases. The observed changes, however, have not been linked to host function and therefore it remains unclear how specific changes in the microbiome alter cellular and molecular pathways within the GI tract. Further, non-invasive techniques to examine the host gene expression profile of the GI mucosa have been described in horses but not evaluated in response to interventions. Therefore, the objectives of our study were to (1) profile gene expression and metabolomic changes in an equine model of non-steroidal anti-inflammatory drug (NSAID)-induced intestinal inflammation and (2) apply computational data integration methods to examine host-microbiota interactions. Methods: Twenty horses were randomly assigned to 1 of 2 groups (n = 10): control (placebo paste) or NSAID (phenylbutazone 4.4 mg/kg orally once daily for 9 days). Fecal samples were collected on days 0 and 10 and analyzed with respect to microbiota (16S rDNA gene sequencing), metabolomic (untargeted metabolites), and host exfoliated cell transcriptomic (exfoliome) changes. Data were analyzed and integrated using a variety of computational techniques, and underlying regulatory mechanisms were inferred from features that were commonly identified by all computational approaches. Results: Phenylbutazone induced alterations in the microbiota, metabolome, and host transcriptome. Data integration identified correlation of specific bacterial genera with expression of several genes and metabolites that were linked to oxidative stress. Concomitant microbiota and metabolite changes resulted in the initiation of endoplasmic reticulum stress and unfolded protein response within the intestinal mucosa. Conclusions: Results of integrative analysis identified an important role for oxidative stress, and subsequent cell signaling responses, in a large animal model of GI inflammation. The computational approaches for combining non-invasive platforms for unbiased assessment of host GI responses (e.g., exfoliomics) with metabolomic and microbiota changes have broad application for the field of gastroenterology. 8RW7XWUKiyvANo7PaYZA3n Video Abstract [ABSTRACT FROM AUTHOR]

The use of anthelminthic drugs has several drawbacks, including the selection of resistant parasite strains. Alternative avenues to mitigate the negative effects of helminth infection involve dietary interventions that might affect resistance and/or tolerance by improving host immunity, modulating the microbiota, or exerting direct anthelmintic effects. The aim of this study was to assess the impact of diet on strongyle infection in horses, specifically through immune-mediated, microbiota-mediated, or direct anthelmintic effects. Horses that were naturally infected with strongyles were fed either a high-fiber or high-starch diet, supplemented with either polyphenol-rich pellets (dehydrated sainfoin) or control pellets (sunflower and hay). When horses were fed a high-starch diet, they excreted more strongyle eggs. Adding sainfoin in the high-starch diet reduced egg excretion. Additionally, sainfoin decreased larval motility whatever the diet. Moreover, the high-starch diet led to a lower fecal bacterial diversity, structural differences in fecal microbiota, lower fecal pH, lower blood acetate, and lower hematocrit compared to the high-fiber diet. Circulating levels of Th1 and Th2 cytokines, lipopolysaccharides, procalcitonin, and white blood cells proportions did not differ between diets. Overall, this study highlights the role of dietary manipulations as an alternative strategy to mitigate the effect of helminth infection and suggests that, in addition to the direct effects, changes in the intestinal ecosystem are the possible underlying mechanism. [ABSTRACT FROM AUTHOR]

Equine asthma (EA) is an important cause of wastage in the USA horse industry. Exposure to organic particulates, from stable dust, airborne pollen, and fungal loads, is posited to be the main cause. Dust arising from the earth's crust has been largely ignored as a contributor to EA in the veterinary literature. The objectives of this study were to investigate the occurrence of birefringent particulates in the bronchoalveolar lavage fluid (BALF) of horses with a clinical complaint of EA residing in the arid West of the USA v. the East, in an effort to determine the contribution of geolocation to geogenic dust exposure. We analyzed BALF cytology and historical data sent to our referral clinical laboratory from 148 horses from the West Coast and 233 horses from the East Coast of the USA over a 6-year period, using light microscopy to determine cell proportions and other visible elements as well as a polarizing lens to detect birefringent material. Univariate analysis showed that horses from the West coast were significantly more likely to have birefringent particulates in the BALF than horses from the East coast (40.5% v. 8.6%, p < 0.001); while horses from the East had higher BALF neutrophil proportions. Horses from the West also had lower proportions of neutrophils in the BALF than those from the East (27.1 v. 10.9, p <.001). Using historical and BAL data in a forward stepwise binary logistic regression model with presence of birefringent particulates found within alveolar macrophages as the outcome, geographical location in the West retained significance as a predictor (OR 8.0, CI [4.3–14.8], p<.001). While the birefringent particulates cannot be identified on the basis of polarizing microscopy alone, this study provides evidence that horses from the West are exposed to inorganic particulates that may contribute to signs of equine asthma. [ABSTRACT FROM AUTHOR]

Equine piroplasmosis (EP) is caused by Theileria (T.) equi and/or Babesia (B.) caballi. The aim was to assess the percentage of positive test results for EP in horses in Europe and to identify risk factors for pathogen contact/infection. This study included results from PCR and competitive enzyme-linked immunosorbent assay testing requested by European veterinarians between 2008 and 2021. Binary bivariate logistic regression was used to analyze risk factors. A total of 4060 horses were included. PCR testing was positive in 9.7% (154/1589), serology for T. equi in 15.2% (393/2591) and for B. caballi in 6.8% (175/2578). The odds of positive serology increased by 6.8% (B. caballi, p = 0.008) and 9.5% (T. equi, p < 0.001) each year. Regionality had a statistically significant impact on PCR (Eastern p = 0.047/OR = 1.605; Southern p = 0.029/OR = 1.451; Central p = 0.007/OR = 0.617) and serological testing for T. equi (Southern p < 0.001/OR = 2.521; Central p < 0.001/OR = 0.537; Northern p = 0.003/OR = 0.462), as well as breeds on seroprevalence of B. caballi (heavy horses: p = 0.016/OR = 2.239) and T. equi (ponies: p = 0.007/OR = 0.340; warmbloods: p = 0.025/OR = 1.602). In conclusion, there was a significant geographical impact on the results of PCR and serology, consistent with known vector habitats. The rising numbers of horses tested serologically positive highlights the importance of surveillance. [ABSTRACT FROM AUTHOR]

Equine influenza virus (EIV) remains a threat to horses, despite the availability of vaccines. Strategies to monitor the virus and prevent potential vaccine failure revolve around serological assays, RT-qPCR amplification, and sequencing the viral hemagglutinin (HA) and neuraminidase (NA) genes. These approaches overlook the contribution of other viral proteins in driving virulence. This study assesses the potential of long-read nanopore sequencing for fast and precise sequencing of circulating equine influenza viruses. Therefore, two French Florida Clade 1 strains, including the one circulating in winter 2018–2019 exhibiting more pronounced pathogenicity than usual, as well as the two currently OIE-recommended vaccine strains, were sequenced. Our results demonstrated the reliability of this sequencing method in generating accurate sequences. Sequence analysis of HA revealed a subtle antigenic drift in the French EIV strains, with specific substitutions, such as T163I in A/equine/Paris/1/2018 and the N188T mutation in post-2015 strains; both substitutions were in antigenic site B. Antigenic site E exhibited modifications in post-2018 strains, with the N63D substitution. Segment 2 sequencing also revealed that the A/equine/Paris/1/2018 strain encodes a longer variant of the PB1-F2 protein when compared to other Florida clade 1 strains (90 amino acids long versus 81 amino acids long). Further biological and biochemistry assays demonstrated that this PB1-F2 variant has enhanced abilities to abolish the mitochondrial membrane potential ΔΨm and permeabilize synthetic membranes. Altogether, our results highlight the interest in rapidly characterizing the complete genome of circulating strains with next-generation sequencing technologies to adapt vaccines and identify specific virulence markers of EIV. [ABSTRACT FROM AUTHOR]

Epithelial damage due to gastrointestinal disorders frequently causes severe disease in horses. To study the underlying pathophysiological processes, we aimed to establish equine jejunum and colon enteroids (eqJE, eqCE) mimicking the in vivo epithelium. Therefore, enteroids were cultivated in four different media for differentiation and subsequently characterized histomorphologically, on mRNA and on protein level in comparison to the native epithelium of the same donor horses to identify ideal culture conditions for an in vitro model system. With increasing enterocyte differentiation, the enteroids showed a reduced growth rate as well as a predominantly spherical morphology and less budding compared to enteroids in proliferation medium. Combined or individual withdrawal of stem cell niche pathway components resulted in lower mRNA expression levels of stem cell markers and concomitant differentiation of enterocytes, goblet cells and enteroendocrine cells. For eqCE, withdrawal of Wnt alone was sufficient for the generation of differentiated enterocytes with a close resemblance to the in vivo epithelium. Combined removal of Wnt, R-spondin and Noggin and the addition of DAPT stimulated differentiation of eqJE at a similar level as the in vivo epithelium, particularly with regard to enterocytes. In summary, we successfully defined a medium composition that promotes the formation of eqJE and eqCE consisting of multiple cell types and resembling the in vivo epithelium. Our findings emphasize the importance of adapting culture conditions to the respective species and the intestinal segment. This in vitro model will be used to investigate the pathological mechanisms underlying equine gastrointestinal disorders in future studies. [ABSTRACT FROM AUTHOR]

Stem cell-derived organoid cultures have emerged as attractive experimental models for infection biology research regarding various types of gastro-intestinal pathogens and host species. However, the large size of infectious nematode larvae and the closed structure of 3-dimensional organoids often hinder studies of the natural route of infection. To enable easy administration to the apical surface of the epithelium, organoids from the equine small intestine, i.e. enteroids, were used in the present study to establish epithelial monolayer cultures. These monolayers were functionally tested by stimulation with IL-4 and IL-13, and/or exposure to infectious stage larvae of the equine nematodes Parascaris univalens, cyathostominae and/or Strongylus vulgaris. Effects were recorded using transcriptional analysis combined with histochemistry, immunofluorescence-, live-cell- and scanning electron microscopy. These analyses revealed heterogeneous monolayers containing both immature and differentiated cells including tuft cells and mucus-producing goblet cells. Stimulation with IL-4/IL-13 increased tuft- and goblet cell differentiation as demonstrated by the expression of DCLK1 and MUC2. In these cytokine-primed monolayers, the expression of MUC2 was further promoted by co-culture with P. univalens. Moreover, live-cell imaging revealed morphological alterations of the epithelial cells following exposure to larvae even in the absence of cytokine stimulation. Thus, the present work describes the design, characterization and usability of an experimental model representing the equine nematode-infected small intestinal epithelium. The presence of tuft cells and goblet cells whose mucus production is affected by Th2 cytokines and/or the presence of larvae opens up for mechanistic studies of the physical interactions between nematodes and the equine intestinal mucosa. [ABSTRACT FROM AUTHOR]

Simple Summary: Equine influenza (EI) is an acute and highly contagious viral disease of equids characterized by fever and respiratory signs. Ongoing antigenic mutations that are typical of influenza viruses, which may cause a reduction in the effectiveness of vaccines, highlight how crucial both surveillance and virus characterization are for updating vaccine compositions. The aim of this study was to verify the identity of the equine influenza virus strains detected in Italy, especially in the absence of formal active surveillance. Twenty nasal swabs, collected from symptomatic horses located in North and Central Italy between February and April 2019 were positive for influenza A virus (IAV) RRT-PCR. Sequencing identified an isolated strain as H3N8 Florida lineage clade 1 for one sample from Brescia, Lombardy Region. This study is the first report of H3N8 Florida lineage clade 1 circulation in Italy, confirming the value of monitoring for EIV circulating strain in relation to the appropriateness of the vaccine virus composition for maximum efficacy. Background: Equine influenza (EI) is a highly contagious viral disease of equids characterized by pyrexia and respiratory signs. Like other influenza A viruses, antigenic drift or shift could lead to a vaccine-induced immunity breakdown if vaccine strains are not updated. The aim of this study was to genetically characterize EIV strains circulating in Italy, detected in PCR-positive samples collected from suspected cases, especially in the absence of formal active surveillance. Methods: Between February and April 2019, blood samples and nasal swabs collected from each of the 20 symptomatic horses from North and Central Italy were submitted to the National Reference Centre for Equine Diseases in Italy to confirm preliminary analysis performed by other laboratories. Results: None of the sera analysed using haemagglutination inhibition and single radial haemolysis presented a predominant serological reactivity pattern for any antigen employed. All nasal swabs were positive with IAV RRT-PCR. Only one strain, isolated in an embryonated chicken egg from a sample collected from a horse of a stable located in Brescia, Lombardy, was identified as H3N8 Florida lineage clade 1 (FC1). In the constructed phylogenetic trees, this strain is located within the FC1, together with the virus isolated in France in 2018 (MK501761). Conclusions: This study reports the first detection of H3N8 FC1 in Italy, highlighting the importance of monitoring circulating EIV strains to verify the vaccine composition appropriateness for maximum efficacy. [ABSTRACT FROM AUTHOR]

In different species, embryonic aneuploidies and genome-wide errors are a major cause of developmental failure. The increasing number of equine embryos being produced worldwide provides the opportunity to characterize and rank or select embryos based on their genetic profile prior to transfer. Here, we explored the possibility of generic, genome-wide preimplantation genetic testing concurrently for aneuploidies (PGT-A) and monogenic (PGT-M) traits and diseases in the horse, meanwhile assessing the incidence and spectrum of chromosomal and genome-wide errors in in vitro-produced equine embryos. To this end, over 70,000 single nucleotide polymorphism (SNP) positions were genotyped in 14 trophectoderm biopsies and corresponding biopsied blastocysts, and in 26 individual blastomeres from six arrested cleavage-stage embryos. Subsequently, concurrent genome-wide copy number detection and haplotyping by haplarithmisis was performed and the presence of aneuploidies and genome-wide errors and the inherited parental haplotypes for four common disease-associated genes with high carrier frequency in different horse breeds (GBE1, PLOD1, B3GALNT2, MUTYH), and for one color coat-associated gene (STX17) were compared in biopsy-blastocyst combinations. The euploid (n = 12) or fully aneuploid (n = 2) state and the inherited parental haplotypes for 42/45 loci of interest of the biopsied blastocysts were predicted by the biopsy samples in all successfully analyzed biopsy-blastocyst combinations (n = 9). Two biopsies showed a loss of maternal chromosome 28 and 31, respectively, which were confirmed in the corresponding blastocysts. In one of those biopsies, additional complex aneuploidies not present in the blastocyst were found. Five out of six arrested embryos contained chromosomal and/or genome-wide errors in most of their blastomeres, demonstrating their contribution to equine embryonic arrest in vitro. The application of the described PGT strategy would allow to select equine embryos devoid of genetic errors and pathogenetic variants, and with the variants of interest, which will improve foaling rate and horse quality. We believe this approach will be a gamechanger in horse breeding. [ABSTRACT FROM AUTHOR]

Background: Equine influenza (EI) is a transmissible viral respiratory sickness of the Equidae family. Two viruses, H7N7 and H3N8 caused EI; however, H7N7 has not been detected for decades. H3N8 has circulated and bifurcated into Eurasian and American lineages. The latter subsequently diversified into Kentucky, South America, and Florida sub-lineages. Florida clade 1 (FC1) and Florida clade 2 (FC2) strains are the only circulating EI viruses (EIVs) in the meantime. Immunization is considered the major means for the prevention and control of EI infection. Using disparate technologies and platforms, several vaccines have been developed and commercialized. According to the recommendations of the World Organization for Animal Health (WOAH), all commercial vaccines shall comprise representatives of both FC1 and FC2 strains. Unfortunately, most of the commercially available vaccines were not updated to incorporate a representative of FC2 strains. Aim: The purpose of this research was to develop a new EI vaccine candidate that incorporates the hemagglutinin (HA) antigen from the currently circulating FC2. Methods: In this study, we report the expression of the full-length recombinant HA gene of FC2 in the baculovirus expression system. Results: The HA recombinant protein has been proven to maintain its biological characteristics by hemadsorption (HAD) and hemagglutination tests. Moreover, using a reference-specific serum, the specificity of the HA has been confirmed through the implementation of immunoperoxidase and western immunoblotting assays. Conclusion: In conclusion, we report the expression of specific biologically active recombinant HA of FC2, which would act as a foundation for the generation of an updated EI subunit or virus vector vaccine candidates. [ABSTRACT FROM AUTHOR]

Background: Dexamethasone is routinely administered to horses but its effect on the antibody response to a commercial EIV/EHV vaccine is unclear. Hypothesis: Horses receiving dexamethasone will have lower postvaccination antibody levels against EIV and EHV‐1 than vaccinated controls. Animals: Fifty‐five healthy adult research horses. Methods: Randomized cohort study. Control (no vaccine, group 1), vaccination only (EIV/EHV‐1/EHV‐4, Prestige 2, Merck Animal Health, group 2), vaccination and concurrent single intravenous dose of dexamethasone (approximately.05 mg/kg, group 3), vaccination and 3 intravenous doses of dexamethasone at 24 hours intervals (group 4). Serum SAA levels were measured on day 1 and day 3. Antibody levels against EIV (hemagglutination inhibition assay, Kentucky 2014 antigen) and EHV‐1 (multiplex ELISA targeting total IgG and IgG 4/7) were measured on day 1 and day 30. Results: Significantly increased mean antibody titers after vaccination were only noted against EIV and only after the vaccination alone (n = 14, prevaccine mean [prvm] 166.9, SD 259.6, 95% CI 16.95‐316.8; postvaccine mean [povm] 249.1, SD 257.2, 95% confidence interval [CI] 100.6‐397.6, P =.02) and the single dose dexamethasone (n = 14, prvm 93.14, SD 72.2, CI 51.45‐134.8; povm 185.1, SD 118, CI 116.7‐253.6, P =.01), but not after multiple doses of dexamethasone (n = 14, prvm 194.3, SD 258.3, CI 45.16‐343.4; povm 240.0, SD 235.7, CI 103.9‐376.1, P >.05). Conclusion: The effect of dexamethasone on the postvaccine antibody response varies depending on the dosing frequency and the antigen‐specific antibody type. [ABSTRACT FROM AUTHOR]

Equine influenza virus (EIV) is highly contagious and causes outbreaks of respiratory disease in horses almost worldwide. Particularly at risk for infection with EIV are "naïve" horses that have had no previous contact with EIV or that have received no or only incomplete primary vaccination. This article is intended, among other things, to give an overview of the scientific findings to date on the immune response of foals to vaccination, which differs from that shown by adult horses due to numerous influencing factors. It will discuss the components of the colostrum (antibodies, cytokines and other maternal cells) and their influence on the immune response of foals. The questions at which age a foal should receive the first vaccination of the primary vaccination against EIV, as well as which vaccination scheme is recommended, are also discussed by summarising the results of numerous scientific studies. This review article is intended to help veterinarians advise their clients on the timing and schedule of primary vaccination against equine influenza in foals based on the individual situation (mare's prepartum vaccination status, foal's age at first vaccination, infection pressure, vaccine availability and practicality) on a scientific basis. Based on new study results regarding the primary vaccination of foals against influenza, it can be summarised that shortening the vaccination intervals leads to a lower humoral immune response against EI, that switching vaccine types leads to a higher humoral immune response against EI and that simultaneous vaccination against influenza, herpes and tetanus does not have a detrimental effect on the humoral immune response against EI. [ABSTRACT FROM AUTHOR]

Vaccines against equine influenza have been available since the late 1960s, but outbreaks continue to occur periodically, affecting both vaccinated and unvaccinated animals. The aim of this study was to systematically evaluate the efficacy of vaccines against influenza A virus in horses (equine IAV). For this, PubMed, CAB abstracts, and Web of Science were searched for controlled trials of equine IAV vaccines published up to December 2020. Forty-three articles reporting equine IAV vaccination and challenge studies in previously naïve equids using an appropriate comparison group were included in a qualitative analysis of vaccine efficacy. A value for vaccine efficacy (VE) was calculated as the percentage reduction in nasopharyngeal virus shedding detected by virus isolation in embryonated hens' eggs from 38 articles. Among 21 studies involving commercial vaccines, the mean VE was 50.03% (95% CI: 23.35–76.71%), ranging from 0 to 100%. Among 17 studies reporting the use of experimental vaccines, the mean VE was 40.37% (95% CI: 19.64–62.44), and the range was again 0–100%. Overall, complete protection from virus shedding was achieved in five studies. In conclusion, although commercially available vaccines can, in some circumstances, offer complete protection from infection, the requirement for frequent vaccination in the field to limit virus shedding and hence transmission is apparent. Although most studies were conducted by a few centres, a lack of consistent study design made comparisons difficult. [ABSTRACT FROM AUTHOR]

Simple Summary: Biosecurity practices are essential to protect the United States horse industry from infectious disease outbreaks. Horse owners' level of knowledge and awareness of biosecurity are not known. To inform the industry, the current practices need to be understood to determine the kind of education needed to improve biosecurity on owners' properties or when traveling to horse events. A survey, which consisted of a website-based questionnaire and collection, was distributed to horse owner organizations' email lists. Evaluation of the results included analysis with a cross-tabulation software to identify significant differences in biosecurity practices associated with horse use and location within the United States. Four areas in the United States were identified (Northeast, Midwest, South and West), and horse use was classified as follows: Pleasure/Trail Riding, Lessons/School, Western Show, English Show, Breeding, Farm/Ranch, Retired, Racing and Driving. In total, 2413 responses were received to the 24-question survey. Differences in biosecurity use and understanding were identified across horse use categories and regions of the country, including differences in the availability of biosecurity plans, risk assessment for horse contact and the use of isolation to mitigate infectious disease. Owners are responsible for medical decision making, and veterinarians are the most trusted resource for medical information. Owners indicated that websites are the preferred way to receive educational information about diseases. There are several biosecurity methods that owners can apply to benefit horse health and welfare. These include temperature monitoring, isolation of new horses at facilities, understanding the risks of horse mingling, knowing the entry requirements such as vaccination and health certificates at events, and having a biosecurity plan for facilities and events where horses come into contact. Horses are transported in the United States more than any other livestock species and co-mingle at various events; therefore, they are considered to be at an increased risk for infectious disease transmission. The fragmented movement of horses combined with numerous sites of co-mingling makes tracing the potential spread of a disease outbreak a necessary part of an infection control plan, both locally and nationally. The cross-movement of personnel with horses and the persistence of endemic diseases make biosecurity implementation an ongoing challenge. Although many of the risks for infection are known, there is limited documentation about the usefulness of prospective control measures. The objective of this survey was to determine horse owners' understanding and knowledge of biosecurity practices for preventing infectious diseases in the United States. Questions covered owner demographic information, including horse use which was divided into 10 categories as follows: Pleasure/Trail Riding, Lessons/School, Western Show, English Show, Breeding, Farm/Ranch, Retired, Racing, Driving and Other. The survey was distributed by sending requests to a list of horse owner organizations, which then sent emails to their members. The email request described the survey and provided a website link to start the survey. A total of 2413 responses were collected. Analysis of the results included cross-tabulation to identify significant differences in biosecurity knowledge and awareness by horse use. Significant differences by horse use were identified for vaccination, biosecurity planning, use of isolation, disease risk, monitoring for diseases, co-mingling of horses, sanitation, medical decision making and health record requirements for horse events. In summary, the results suggest that most owners are not highly concerned about the risk of disease or the use of biosecurity. There are several biosecurity applications and techniques which can be increased and will benefit horse health and welfare. These include reliance on temperature monitoring, isolation of new horses at facilities, risks of horse mingling, entry requirements such as vaccination and health certificates at events, and an emphasis on having biosecurity plans for facilities and events where horses co-mingle. The information from this study will be used to create tools and information that horse owners and veterinarians can use to implement appropriate biosecurity practices for different types of horse uses and events. [ABSTRACT FROM AUTHOR]

O-acetylation is a common modification of sialic acids that has been implicated in a multitude of biological and disease processes. A lack of analytical methods that can determine exact structures of sialic acid variants is a hurdle to determine roles of distinct O-acetylated sialosides. Here, we describe a drift tube ion mobility-mass spectrometry approach that can elucidate exact O-acetylation patterns as well as glycosidic linkage types of sialosides isolated from complex biological samples. It is based on the use of a library of synthetic O-acetylated sialosides to establish intrinsic collision cross section (CCS) values of diagnostic fragment ions. The CCS values were used to characterize O-acetylated sialosides from mucins and N-linked glycans from biologicals as well as equine tracheal and nasal tissues. It uncovered contrasting sialic acid linkage types of acetylated and non-acetylated sialic acids and provided a rationale for sialic acid binding preferences of equine H7 influenza A viruses. O-acetylation is a common modification of sialic acids. Here, a library of synthetic O-acetylated sialosides made it possible to develop an ion mobility mass spectrometry (IM-MS) approach that can elucidate exact O-acetylation patterns and glycosidic linkage types of sialosides isolated from biological samples. [ABSTRACT FROM AUTHOR]

Equine piroplasmosis (EP) is a parasitic disease caused by Theileria equi (T. equi), Babesia caballi (B. caballi) and Theileria haneyi (T. haneyi). This disease is considered to be reportable by the World Organization for Animal Health (WOAH). Real-time quantitative PCR (qPCR) is regarded as a straightforward, rapid and sensitive diagnostic method to detect pathogens. However, qPCR has not been employed in the various epidemiological investigations of T. haneyi. In this study, we developed a new qPCR method to detect T. haneyi based on the chr1sco (chromosome 1 single-copy open reading frame (ORF)) gene, which has no detectable orthologs in T. equi or B. caballi. A TaqMan MGB probe was used in the development of the qPCR assay. A plasmid containing the chr1sco gene was constructed and used to establish the standard curves. The novel qPCR technique demonstrated great specificity for detecting additional frequent equine infectious pathogens and sensitivity for detecting diluted standard plasmids. This qPCR was further validated by comparison with an optimized nested PCR (nPCR) assay in the analysis of 96 clinical samples. The agreement between the nPCR assay and the established qPCR assay was 85.42%. The newly established method could contribute to the accurate diagnosis of T. haneyi infections in horses. [ABSTRACT FROM AUTHOR]

Simple Summary: Angiogenesis, the sprouting of new capillaries from existing vessels, plays a crucial role in various physiological processes. Pathological vascularization, as seen in, e.g., cancer, musculoskeletal diseases, or ocular disorders, eventually causes tissue and organ dysfunctions. Vascular endothelial growth factor A (VEGF-A) and its receptors are known to play a key role in angiogenesis; therefore, targeting the VEGF pathway represents one of the main areas of human cancer research in recent years. So far, anti-VEGF treatment in horses has not been investigated. In this study, the effect of bevacizumab, the most widespread anti-VEGF agent, on an equine cell line harvested from umbilical cords was investigated. Bevacizumab efficiently inhibited various cellular processes associated with angiogenesis and could therefore be a promising therapeutic approach in vascular-driven diseases in horses. Anti-VEGF agents were found to have clinical implications for the successful treatment of vascular-driven diseases in humans. In this study, a detailed biological characterization of bevacizumab in a variety of in vitro assays was carried out to determine the effect of bevacizumab on equine umbilical vein endothelial cells (EqUVEC). EqUVECs were harvested from umbilical cords of clinically healthy horses and exposed to different concentrations (1, 2, 4, 6, 8 mg/mL) of bevacizumab (Avastin®). Assays concerning the drug's safety (cell viability and proliferation assay) and efficacy (cell tube formation assay, cell migration assay, and Vascular endothelial growth factor (VEGF) expression) were carried out reflecting multiple cellular processes. Bevacizumab significantly decreased VEGF expression at all concentrations over a 72 h period. No cytotoxic effect of bevacizumab on EqUVECs was observed at concentrations of 4 mg/mL bevacizumab or lower. Incubated endothelial cells showed delayed tube formation and bevacizumab efficiently inhibited cell migration in a dose-dependent manner. Bevacizumab potently inhibits VEGF-induced cellular processes and could be a promising therapeutic approach in vascular-driven diseases in horses. [ABSTRACT FROM AUTHOR]

Equine rhinitis B virus is a lesser-known equine respiratory pathogen that is being detected with increasing frequency via a voluntary upper respiratory biosurveillance program in the United States. This program received 8684 nasal swab submissions during the years 2012–2023. The nasal swabs were submitted for qPCR testing for six common upper respiratory pathogens: Streptococcus equi subspecies equi (S. equi), equine influenza virus (EIV), equine herpesvirus type 1 (EHV-1), equine herpesvirus type 4 (EHV-4), equine rhinitis A virus (ERAV), and equine rhinitis B virus (ERBV). The overall ERBV qPCR-positivity rate was 5.08% (441/8684). ERBV was detected as a single pathogen in 291 cases (65.99% of positives, 291/441) and was detected as a coinfection with at least one other respiratory pathogen in 150 cases (34.01%, 150/441). Young horses, less than a year of age, with acute onset of fever and respiratory signs and horses used for competition are more likely to test qPCR-positive for ERBV. Horses with ERBV may present with fever, nasal discharge, ocular discharge, and/or cough. Coinfection is a common feature of ERBV infection and S. equi, EHV-4 and EIV were the most common pathogens coinfected with ERBV. This report provides important information regarding the clinical relevance of ERBV in the horse and begins investigating the impact of coinfection on clinical disease. [ABSTRACT FROM AUTHOR]

The American Association of Equine Practitioners strongly advocates evidence-based intestinal strongyle control in horses. It recommends targeted treatment of all heavy egg shedders (>500 eggs per gram (EPG) of feces), while the low shedders (0–200 EPG) are left untreated. As 50–75% of adult horses in a herd are low shedders, preventing them from unnecessary anthelmintic exposure is critical for tackling resistance. There are various fecal egg count (FEC) techniques with many modifications and variations in use, but none is identified as a gold standard. The hypothesis of the study was that the diagnostic performance of 12 commonly used quantitation methodologies (three techniques with four variants) differs. In this regard, method comparison studies were performed using polystyrene beads as proxy for intestinal strongyle eggs. Mini-FLOTAC-based variants had the lowest coefficient of variation (CV%) in bead recovery, whereas McMaster variants had the highest. All four variants of Mini-FLOTAC and the NaNO3 1.33 specific gravity variant of modified Wisconsin followed a linear fit with R2 > 0.95. In contrast, the bead standard replicates for modified McMaster variants dispersed from the regression curve, causing a lower R2. The Mini-FLOTAC method seems less influenced by the choice of floatation solution and has better repeatability parameters and linearity for bead standard recovery. For FEC tests with high R2 (>0.95) but that underestimated the true bead count, a correction factor (CF) was determined to estimate the true count. Finally, the validity of CF was analyzed for 5 tests with R2 > 0.95 to accurately quantify intestinal strongyle eggs from 40 different horses. Overall, this study identified FEC methodologies with the highest diagnostic performance. The limitations in standardizing routine FEC tests are highlighted, and the importance of equalization of FEC results is emphasized for promoting uniformity in the implementation of parasite control guidelines. [ABSTRACT FROM AUTHOR]

Background and Aim: Equine influenza (EI) is a highly contagious disease that causes fever and upper respiratory tract inflammation. It is caused by influenza virus A, belonging to the Orthomyxoviridae family, with subtypes H3N8 and H7N7. This study presents data on the development of a real-time polymerase chain reaction (RT-PCR) assay using TaqMan probes to detect the H3 subtype of EI virus (EIV). Materials and Methods: The evaluation of the developed RT-PCR assay involved five strains of EIV as positive controls and ten nasopharyngeal swab samples collected from horses. RNA was isolated using the GeneJet Viral DNA and RNA Purification Kit, and primers and probes were designed using the Integrated DNA Technology PrimerQuest Tool. The assay was optimized by investigating the annealing temperature, primer and probes concentrations, sensitivity, and specificity. Sequencing was performed using the Thermo Fisher 3130 Genetic Analyzer, and the evolutionary history was inferred using the Neighbor-Joining method. Results: The designed primers and probes, targeting the H3 gene, were found to be specific to the EIV. The RT-PCR assay was capable of detecting as low as 50 femtogram (f) or 3 × 103 copies of genomic RNA. No cross-reactions were observed with other respiratory viral and bacterial pathogens, indicating the high specificity of the assay. To evaluate its effectiveness, ten nasopharyngeal swab samples collected from farms in North Kazakhstan regions during disease monitoring were analyzed. The accuracy of the analysis was confirmed by comparing the results with those obtained from a commercial RT-PCR assay for EI identification. The developed RT-PCR assay exhibited high sensitivity and specificity for detecting the EIV. Conclusion: The results demonstrate that the developed RT-PCR assay is suitable for diagnosing EI. This simple, highly sensitive, and specific assay for detecting H3 EIV can be a reliable tool for diagnosing and surveilling EI. Implementing this RT-PCR assay in veterinary practice will enhance and expedite the timely response to potential outbreaks of EI, thus positively impacting the overall epizootic well-being of EI in Kazakhstan.

Equine influenza is a viral disease caused by the equine influenza virus (EIV), and according to the WOAH, it is mandatory to report these infections. In Latin America and Colombia, EIV risk factors have not been analyzed. The objective of this research is to perform an epidemiological and molecular analysis of the EIV in horses with respiratory symptoms from 2020 to 2023 in Colombia. Molecular EIV detection was performed using RT–qPCR and nanopore sequencing. A risk analysis was also performed via the GEE method. A total of 188 equines with EIV respiratory symptoms were recruited. The positivity rate was 33.5%. The descriptive analysis showed that only 12.8% of the horses were vaccinated, and measures such as the quarantine and isolation of symptomatic animals accounted for 91.5% and 88.8%, respectively. The variables associated with the EIV were the non-isolation of positive individuals (OR = 8.16, 95% CI (1.52–43.67), p = 0.014) and sharing space with poultry (OR = 2.16, 95% CI (1.09–4.26), p = 0.027). In conclusion, this is the first EIV investigation in symptomatic horses in Colombia, highlighting the presence of the virus in the country and the need to improve preventive and control measures.

Equine influenza virus (EIV) causes acute respiratory disease in horses and belongs to the influenza A virus family Orthomyxoviridae, genus Orthomyxovirus. This virus may have severe financial implications for the horse industry owing to its highly contagious nature and rapid transmission. In the Republic of Korea, vaccination against EIV has been practiced with the active involvement of the Korea Racing Authority since 1974. In this study, we monitored the viral RNA for EIV using PCR, as well as the antibody levels against 'A/equine/South Africa/4/03 (H3N8, clade 1)', from 2020 to 2022. EIV was not detected using RT-PCR. The seropositivity rates detected using a hemagglutination inhibition assay were 90.3% in 2020, 96.7% in 2021, and 91.8% in 2022. The geometric mean of antibody titer (GMT) was 83.4 in 2020, 135.7 in 2021, and 95.6 in 2022. Yearlings and two-year-olds in training exhibited lower positive rates (59.1% in 2020, 38.9% in 2021, and 44.1% in 2022) than the average. These younger horses may require more attention for vaccination and vaccine responses against EIV. Continuous surveillance of EIV should be performed to monitor the prevalence and spread of this disease. [ABSTRACT FROM AUTHOR]

The aim of this study was to use environmental sampling to determine the frequency of detection of selected equine respiratory viruses and bacteria in horses attending a multi-week equestrian show during the winter months. At four time points during showing, environmental sponge samples were collected from all stalls on the property and tested for the presence of equine herpesvirus-1 (EHV-1), EHV-2, EHV-4, equine influenza virus (EIV), equine rhinitis B virus (ERBV), Streptococcus equi ss. equi (S. equi), and S. equi ss. zooepidemicus (S. zooepidemicus) using real-time PCR (PCR). Environmental sponges were collected from all 53 barns by using one sponge for up to 10 stalls. Further, 2/53 barns were randomly selected for individual stall sampling in order to compare the results between individual and pooled stall samples. A total of 333/948 (35.13%, 95% CI 32.09–38.26%) pooled environmental stall sponges tested PCR-positive for at least one of the selected respiratory pathogens. Streptococcus zooepidemicus was the most commonly detected pathogen in pooled samples (28.69%, 95% CI 25.83–31.69%), followed by EHV-2 (14.45%, 95% CI 12.27–16.85%), EHV-4 (1.37%, 95% CI 0.73–2.33%), and a very small percentage of pooled stall sponges tested PCR-positive for EHV-1, ERBV, EIV, and S. equi. In individual samples, 171/464 (36.85%, 95% CI 32.45–41.42%) environmental stall sponges tested PCR-positive for at least one of the selected pathogens, following a similar frequency of pathogen detection as pooled samples. The detection frequency of true respiratory pathogens from environmental samples was higher during the winter months compared to previous studies performed during spring and summer, and this testing highlights that such pathogens circulate with greater frequency during the colder months of the year. The strategy of monitoring environmental stall samples for respiratory pathogens circumvents the often labor-intensive collection of respiratory secretions from healthy horses and allows for a more efficient assessment of pathogen buildup over time. However, environmental stall testing for respiratory pathogens should not replace proper biosecurity protocols, but it should instead be considered as an additional tool to monitor the silent circulation of respiratory pathogens in at-risk horses. [ABSTRACT FROM AUTHOR]

Equine asthma (EA) is a heterogenous, complex disease, with a significant negative impact on horse welfare and performance. EA and human asthma share fundamental similarities, making EA a useful model for studying the disease. One relevant sample type for investigating chronic lung inflammation is bronchoalveolar lavage fluid (BALF), which provides a snapshot of the immune cells present in the alveolar space. To investigate the immune cell landscape of the respiratory tract in horses with mild-to-moderate equine asthma (mEA) and healthy controls, single-cell RNA sequencing was conducted on equine BALF cells. We characterized the major immune cell populations present in equine BALF, as well as subtypes thereof. Interestingly, the most significantly upregulated gene discovered in cases of mEA was FKBP5, a chaperone protein involved in regulating the activity of the glucocorticoid receptor. [ABSTRACT FROM AUTHOR]

Centromeres are epigenetically specified by the histone H3 variant CENP-A. Although mammalian centromeres are typically associated with satellite DNA, we previously demonstrated that the centromere of horse chromosome 11 (ECA11) is completely devoid of satellite DNA. We also showed that the localization of its CENP-A binding domain is not fixed but slides within an about 500 kb region in different individuals, giving rise to positional alleles. These epialleles are inherited as Mendelian traits but their position can move in one generation. It is still unknown whether centromere sliding occurs during meiosis or during development. Here, we first improve the sequence of the ECA11 centromeric region in the EquCab3.0 assembly. Then, to test whether centromere sliding may occur during development, we map the CENP-A binding domains of ECA11 using ChIP-seq in five tissues of different embryonic origin from the four horses of the equine FAANG (Functional Annotation of ANimal Genomes) consortium. Our results demonstrate that the centromere is localized in the same region in all tissues, suggesting that the position of the centromeric domain is maintained during development. Sequence improvement of the centromeric region of horse chromosome 11 and mapping of the histone H3 variant CENP-A binding domains show that the centromere is localized in the same region in horse tissues from different embryonic origin. [ABSTRACT FROM AUTHOR]

Simple Summary: Severe equine asthma is an allergic disease and commonly affects adult horses, resulting in increased respiratory effort, nasal discharge and cough. Human patients affected by allergic diseases tend to present a lower gastrointestinal parasitic burden, when compared to healthy individuals. The present study intended to ascertain if this tendency would also be observed in a group of non-related severely asthmatic horses living in a Mediterranean climate. Thus, the number of gastrointestinal parasites shed by severely asthmatic and non-asthmatic horses from the same farms subjected to a similar management and deworming program were compared. The horses diagnosed with severe equine asthma shed a lower number of parasitic eggs and infective larvae in comparison to their healthy mates. This being a brief report, there is still the need to ascertain if this occurs in a larger population of horses; in addition, further research is necessary to understand the mechanisms behind this process. The relationship between helminth infection and allergic diseases has long intrigued the scientific community. This interaction was previously studied in a horse family with high incidence of severe equine asthma and in non-related severely asthmatic horses from equine hospital referrals in Switzerland. Our aim was to determine if this interaction would also be observed in a group of non-related client-owned severely asthmatic horses living in a Mediterranean climate and recruited through a first-opinion veterinarian group. Fecal samples from severe equine asthma-affected and healthy horses living in the same farms and subjected to identical environmental and deworming management were evaluated qualitatively and quantitatively. Strongyle-type eggs and Cyathostomum sensu latum larvae were the most abundant parasites in the studied population of horses; no significant differences between the groups were observed regarding the types of egg and infective larvae. However, we observed significant differences in the number of eggs and infective larvae per gram of feces shed, as this number was significantly lower in the SEA group than in the healthy horses. This may indicate that severely asthmatic horses have an intrinsic resistance to gastrointestinal helminths. Further studies in a larger population of horses are required to ascertain the immunological mechanisms responsible for these findings. [ABSTRACT FROM AUTHOR]

Background and Aim: Equine influenza (EI) is a highly contagious disease that causes fever and upper respiratory tract inflammation. It is caused by influenza virus A, belonging to the Orthomyxoviridae family, with subtypes H3N8 and H7N7. This study presents data on the development of a real-time polymerase chain reaction (RT-PCR) assay using TaqMan probes to detect the H3 subtype of EI virus (EIV). Materials and Methods: The evaluation of the developed RT-PCR assay involved five strains of EIV as positive controls and ten nasopharyngeal swab samples collected from horses. RNA was isolated using the GeneJet Viral DNA and RNA Purification Kit, and primers and probes were designed using the Integrated DNA Technology PrimerQuest Tool. The assay was optimized by investigating the annealing temperature, primer and probes concentrations, sensitivity, and specificity. Sequencing was performed using the Thermo Fisher 3130 Genetic Analyzer, and the evolutionary history was inferred using the Neighbor-Joining method. Results: The designed primers and probes, targeting the H3 gene, were found to be specific to the EIV. The RT-PCR assay was capable of detecting as low as 50 femtogram (f) or 3 × 10³ copies of genomic RNA. No cross-reactions were observed with other respiratory viral and bacterial pathogens, indicating the high specificity of the assay. To evaluate its effectiveness, ten nasopharyngeal swab samples collected from farms in North Kazakhstan regions during disease monitoring were analyzed. The accuracy of the analysis was confirmed by comparing the results with those obtained from a commercial RT-PCR assay for EI identification. The developed RT-PCR assay exhibited high sensitivity and specificity for detecting the EIV. Conclusion: The results demonstrate that the developed RT-PCR assay is suitable for diagnosing EI. This simple, highly sensitive, and specific assay for detecting H3 EIV can be a reliable tool for diagnosing and surveilling EI. Implementing this RT-PCR assay in veterinary practice will enhance and expedite the timely response to potential outbreaks of EI, thus positively impacting the overall epizootic well-being of EI in Kazakhstan. [ABSTRACT FROM AUTHOR]

Background: Equine influenza (EI) is a highly contagious viral disease of equids characterized by pyrexia and respiratory signs. Like other influenza A viruses, antigenic drift or shift could lead to a vaccine-induced immunity breakdown if vaccine strains are not updated. The aim of this study was to genetically characterize EIV strains circulating in Italy, detected in PCR-positive samples collected from suspected cases, especially in the absence of formal active surveillance. Methods: Between February and April 2019, blood samples and nasal swabs collected from each of the 20 symptomatic horses from North and Central Italy were submitted to the National Reference Centre for Equine Diseases in Italy to confirm preliminary analysis performed by other laboratories. Results: None of the sera analysed using haemagglutination inhibition and single radial haemolysis presented a predominant serological reactivity pattern for any antigen employed. All nasal swabs were positive with IAV RRT-PCR. Only one strain, isolated in an embryonated chicken egg from a sample collected from a horse of a stable located in Brescia, Lombardy, was identified as H3N8 Florida lineage clade 1 (FC1). In the constructed phylogenetic trees, this strain is located within the FC1, together with the virus isolated in France in 2018 (MK501761). Conclusions: This study reports the first detection of H3N8 FC1 in Italy, highlighting the importance of monitoring circulating EIV strains to verify the vaccine composition appropriateness for maximum efficacy.

Simple Summary: The domestic donkey is an endangered equid species. There are 199 donkeys in the Special Nature Reserve "Zasavica", out of the estimated 1000 that are assumed to exist in Serbia. The aim of this study was to assess the exposure of donkeys in the Special Nature Reserve "Zasavica" to some of the most significant viral pathogens and establish the seroprevalence of equine infectious anemia, African horse sickness, equine herpesvirus type 1 infection, equine influenza and equine viral arteritis. In tested blood samples, antibodies against equine herpesvirus type 1 and equine influenza virus (subtype H3N8) were found, while all samples tested negative for African horse sickness virus, equine infectious anemia virus and equine arteritis virus. To our knowledge, this study represents the first results of detection of these pathogens in the population of domestic donkeys in Serbia. The paper presents the findings of specific antibodies in the blood sera of donkeys against the following viruses: equine infectious anemia virus (EIAV), African horse sickness virus (AHSV), equine herpesvirus type 1 (EHV-1), equine influenza virus subtype H3N8 (EIV) and equine arteritis virus (EAV). The analyses were conducted during the year 2022. From a total of 199 donkeys bred in "Zasavica", blood was sampled from 53 animals (2 male donkeys and 51 female donkeys), aged 3 to 10 years. Specific antibodies against EIAV were not detected in any of the tested animals using the agar-gel immunodiffusion (AGID) assay. No specific antibodies against AHSV, tested by enzyme-linked immunosorbent assay (ELISA), or antibodies against EAV, tested by the virus neutralization test (VNT) and ELISA were detected in any of these animals. A positive serological result for EHV-1 was determined by the VNT in all animals, with antibody titer values ranging from 1:2 to 1:128, while a very low antibody titer value for EIV (subtype H3N8) of 1:16 was determined in 18 donkeys using the hemagglutination inhibition test (HI test). [ABSTRACT FROM AUTHOR]

Cross-species virus transmission events can lead to dire public health emergencies in the form of epidemics and pandemics. One example in animals is the emergence of the H3N8 equine influenza virus (EIV), first isolated in 1963 in Miami, FL, USA, after emerging among horses in South America. In the early 21st century, the American lineage of EIV diverged into two 'Florida' clades that persist today, while an EIV transferred to dogs around 1999 and gave rise to the H3N8 canine influenza virus (CIV), first reported in 2004. Here, we compare CIV in dogs and EIV in horses to reveal their host-specific evolution, to determine the sources and connections between significant outbreaks, and to gain insight into the factors controlling their different evolutionary fates. H3N8 CIV only circulated in North America, was geographically restricted after the first few years, and went extinct in 2016. Of the two EIV Florida clades, clade 1 circulates widely and shows frequent transfers between the USA and South America, Europe and elsewhere, while clade 2 was globally distributed early after it emerged, but since about 2018 has only been detected in Central Asia. Any potential zoonotic threat of these viruses to humans can only be determined with an understanding of its natural history and evolution. Our comparative analysis of these three viral lineages reveals distinct patterns and rates of sequence variation yet with similar overall evolution between clades, suggesting epidemiological intervention strategies for possible eradication of H3N8 EIV. [ABSTRACT FROM AUTHOR]

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Recent removal and relocation of feral donkeys from vast public lands to more concentrated holding pens, training facilities, and offsite adoption locations raises several health and welfare concerns. Very little is known regarding the common equid pathogens that are circulating within the feral donkey population in and around Death Valley National Park, California, USA. The aim of this study was to utilize serologic assays to assess previous exposure of these donkeys to equine herpesvirus 1 (EHV-1), equine influenza (EIV), West Nile virus (WNV), and Borrelia burgdorferi (the causative agent of Lyme disease). The results of this study indicate that this feral equid population is mostly naïve and likely susceptible to these common equid pathogens upon removal from the wild.

Abstract Background Equine influenza is an important cause of respiratory disease in equids. The causative virus; EIV, is highly variable and can evolve by accumulation of mutations, particularly in the haemagglutinin (HA) gene. Currently, H3N8 is the sole subtype circulating worldwide with Florida clade 1 (FC1) is most prevalent in the Americas and FC2 in Asia and Europe. In Egypt, EIV was detected in two occasions: subtype H7N7 in 1989 and subtype H3N8 (FC1) in 2008. No data is available on the circulation pattern of EIV during the last decade despite frequent observation of suspected cases. Methods Twenty-two nasal swabs were collected from vaccinated and non-vaccinated horses showing respiratory signs suggestive of EIV infection in 2017–18. Three additional swabs were retrieved during a national race event in January 2018 from Arabian mares with high fever, gait stiffness and dry cough. Samples were screened by RT-qPCR and HA1 domain of the hemagglutinin gene was amplified and sequenced for sequence and phylogenetic analysis. Results RT-qPCR screening revealed that only the 3 samples from the race were positive with cycle thresholds ranging from 16 to 21 indicating high viral load. Isolation attempts in hen’s eggs were unsuccessful. Sequence analysis of the HA1 domain gene has revealed two identical nucleotide sequences, while the third contained 3 synonymous mutations. Phylogenetic analysis clustered study sequences with recent FC2 sequences from Europe. Amino acid alignments revealed 14 and 13 amino acid differences in the study sequences compared to A/equine/Egypt/6066NANRU-VSVRI/08 (H3N8) and A/equine/Kentucky/1997 (H3N8), respectively, available as EIV vaccines in Egypt. Nine amino acids were different from A/equine/Richmond/1/2007 (H3N8), the recommended FC2 vaccine strain by the world organization of animal health expert surveillance panel (OIE-ESP), two of which were unique to the Egyptian sequences while the remaining 7 changes were shared with the FC2-144V subgroup detected in the United Kingdom from late 2015 to 2016. Conclusions The study represents the first reported detection of FC2-144V related EIV from Arabian mares in Egypt, and probably from the entire middle east region. The presented information about EIV epidemiology and spread may require reconsideration of the vaccine strains used in the national vaccination programs.

Influenza A viruses (IAV) cause persistent epidemics and occasional human pandemics, leading to considerable economic losses. The ecology and epidemiology of IAV are very complex and the emergence of novel zoonotic pathogens is one of the greatest challenges in the healthcare. IAV are characterized by genetic and antigenic variability resulting from a combination of high mutation rates and a segmented genome that provides the ability to rapidly change and adapt to new hosts. In this context, available scientific evidence is of great importance for understanding the epidemiology and evolution of influenza viruses. The present review summarizes original research papers and IAV infections reported in dogs all over the world. Reports of interspecies transmission of equine influenza viruses (EIV) H3N2 from birds to dogs, as well as double and triple reassortant strains resulting from reassortment of avian, human and canine strains have amplified the genetic variety of canine influenza viruses. A total of 146 articles were deemed acceptable by PubMed and the Google Scholar database and were therefore included in this review. The largest number of research articles (n=68) were published in Asia, followed by the Americas (n=44), Europe (n=31), Africa (n=2) and Australia (n=1). Publications are conventionally divided into three categories. The first category (largest group) included modern articles published from 2011 to the present (n=93). The second group consisted of publications from 2000 to 2010 (n=46). Single papers of 1919, 1931, 1963, 1972, 1975, and 1992 were also used, which was necessary to emphasize the history of the study of the ecology and evolution of the IAV circulating among various mammalian species. The largest number of publications occurred in 2010 (n=18) and 2015 (n=11), which is associated with IAV outbreaks observed at that time in the dog population in America, Europe and Asia. In general, these findings raise concerns that dogs, may mediate the adaptation of IAVs to zoonotic transmission and therefore serve as alternative hosts for genetic reassortment of these viruses. The global concern and significant threat to public health from the present COVID-19 pandemic confirms the necessity for active surveillance of zoonotic viral diseases with pandemic potential. [Open Vet J 2022; 12(5.000): 676-687]

OBJECTIVE To investigate the effects of interleukin-1β (IL-1β) and methylprednisolone acetate (MPA) on equine intrabursal deep digital flexor tendon (DDFT) and navicular bone fibrocartilage (NBF) cells in vitro. SAMPLE Third passage DDFT and NBF cells from 5 healthy donor horses ages 11–17 years euthanized for reasons unrelated to musculoskeletal conditions. PROCEDURES Aggregate cultures were incubated with culture medium alone (control), 10 ng/mL IL-1β, 10 ng/mL IL-1β + 0.05 mg/mL MPA, or 10 ng/mL IL-1β + 0.5 mg/mL MPA for 24 hours. Extracellular matrix (ECM) gene expressions were assessed via real-time polymerase chain reaction (rtPCR). Culture media matrix metalloproteinase (MMP) -3 and -13 concentrations were quantified via ELISA. Total glycosaminoglycan (GAG) content in the cell pellets and culture media was also assessed. RESULTS IL-1β and IL-1β combined with MPA significantly downregulated ECM gene expression to a greater extent in NBF cells compared with DDFT cells. IL-1β and IL-1β combined with MPA significantly upregulated MMP-3 culture media concentrations in DDFT cells only, and MMP-13 culture media concentrations to a greater extent in NBF cells com- pared with DDFT cells. CLINICAL RELEVANCE NBF cells were more susceptible to IL-1β and MPA-mediated ECM gene expression downregulation in vitro. These results serve as a first step for future work to determine intrabursal corticosteroid regimens that limits or resolve the inflammation as well as take into consideration NBF cell biosynthesis in horses with navicular disease, for which currently no information exists. [ABSTRACT FROM AUTHOR]

Simple Summary: Using the Nanopore platform, we determined the whole genome sequence of an H3N8 equine influenza virus, identified from a 2005 outbreak in Apulia, Italy. The virus was closely related (>99% at the nucleotide level) in all the genome segments to viruses identified in Poland in 2005–2008 and was an inter-lineage multi-reassortant between Florida 2 and Eurasian viruses. Massive sequencing techniques have allowed us to develop straightforward approaches for the whole genome sequencing of viruses, including influenza viruses, generating information that is useful for improving the levels and dimensions of data analysis, even for archival samples. Using the Nanopore platform, we determined the whole genome sequence of an H3N8 equine influenza virus, identified from a 2005 outbreak in Apulia, Italy, whose origin had remained epidemiologically unexplained. The virus was tightly related (>99% at the nucleotide level) in all the genome segments to viruses identified in Poland in 2005–2008 and it was seemingly introduced locally with horse trading for the meat industry. In the phylogenetic analysis based on the eight genome segments, strain ITA/2005/horse/Bari was found to cluster with sub-lineage Florida 2 in the HA and M genes, whilst in the other genes it clustered with strains of the Eurasian lineage, revealing a multi-reassortant nature. [ABSTRACT FROM AUTHOR]

Alveolar macrophages (AMs) are the predominant innate immune cell in the distal respiratory tract. During inflammatory responses, AMs may be supplemented by blood monocytes, which differentiate into monocyte-derived macrophages (MDMs). Macrophages play important roles in a variety of common equine lower airway diseases, including severe equine asthma (SEA). In an experimental model, an inhaled mixture of Aspergillus fumigatus spores, lipopolysaccharide, and silica microspheres (FLS), induced SEA exacerbation in susceptible horses. However, whether equine AMs and MDMs have differing immunophenotypes and cytokine responses to FLS stimulation is unknown. To address these questions, alveolar macrophages/monocytes (AMMs) were isolated from bronchoalveolar lavage fluid and MDMs derived from blood of six healthy horses. Separately, AMMs and MDMs were cultured with and without FLS for six hours after which cell surface marker expression and cytokine production were analyzed by flow cytometry and a bead-based multiplex assay, respectively. Results showed that regardless of exposure conditions, AMMs had significantly higher surface expression of CD163 and CD206 than MDMs. Incubation with FLS induced secretion of IL-1β, IL-8, TNF-α and IFN-γ in AMMs, and IL-8, IL-10 and TNF-α in MDMs. These results suggest that AMMs have a greater proinflammatory response to in vitro FLS stimulation than MDMs, inferring differing roles in equine lung inflammation. Variability in recruitment and function of monocyte-macrophage populations warrant more detailed in vivo investigation in both homeostatic and diseased states. [ABSTRACT FROM AUTHOR]

Background: Laminitis is a complex and debilitating disease of horses. Numerous predisposing factors contribute to laminitis development, however the exact pathogenesis remains undetermined. Serum T4, cortisol, and histamine are components of the innate stress response and could play a causative or contributory role. Stress hormone concentrations in laminitis are largely unknown. Objective: To evaluate parameters associated with stress response in horses with laminitis, and compare these to healthy horses and horses with gastrointestinal (GI) disease. Methods: Thirty-eight adult horses presenting for non-medical conditions, GI abnormalities, or clinical laminitis were prospectively enrolled. Horses were assigned to the appropriate disease group (healthy, GI disease, and laminitis) and had blood drawn on presentation to the hospital. Samples were analyzed for plasma endogenous adrenocorticotrophic hormone (eACTH), serum cortisol, serum thyroid hormone, and plasma histamine. Results: Stress hormone concentrations were significantly different between horses in the laminitis and GI disease groups. Plasma histamine levels were highest in horses with laminitis, compared with GI disease and controls. Both horses with laminitis and GI disease had increased plasma eACTH when compared to healthy horses. Horses with GI disease had higher serum cortisol concentrations than horses with laminitis or controls. Serum T4 was lower in horses with GI disease than in horses with laminitis and controls. Conclusions: Horses with laminitis had relative increases in both plasma histamine and eACTH concentrations. Serum T4 and cortisol concentrations of horses with laminitis did not differ significantly when compared to healthy horses. The role of stress hormones in equine disease warrants further investigation. [ABSTRACT FROM AUTHOR]

A voluntary upper respiratory biosurveillance program in the USA received 9740 nasal swab submissions during the years 2008–2021 from 333 veterinarians and veterinary clinics. The nasal swabs were submitted for qPCR testing for six common upper respiratory pathogens:equine influenza virus (EIV), equine herpesvirus-1 (EHV-1), equine herpesvirus-4 (EHV-4), Streptococcus equi subspecies equi (S. equi), equine rhinitis A virus (ERAV), and equine rhinitis B virus (ERBV). Additional testing was performed for equine gamma herpesvirus-2 (EHV-2) and equine gamma herpesvirus-5 (EHV-5) and the results are reported. Basic frequency statistics and multivariate logistic regression models were utilized to determine the associations between risk factors and EIV positivity. The EIV qPCR-positivity rate was 9.9%. Equids less than 9 years of age with a recent history of travel and seasonal occurrence in winter and spring were the most common population that were qPCR positive for EIV. This ongoing biosurveillance program emphasizes the need for molecular testing for pathogen identification, which is critical for decisions associated with therapeutics and biosecurity intervention for health management and vaccine evaluations and development. [ABSTRACT FROM AUTHOR]