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Equine influenza virus (EIV) causes severe acute respiratory disease in horses. Currently, the strains belonging to the H3N8 genotype are divided into two clades, Florida clade 1 (FC1) and Florida clade 2 (FC2) which emerged in 2002. Both FC1and FC2 clades were reported in Asian and Middle East countries in the last decade. In this study, we described the evolution, epidemiology and molecular characteristic of the EIV lineages, with focus on those detected in Asia from 2007 to 2017. The full genome phylogeny showed that FC1 and FC2 constituted separated and divergent lineages, without evidence of reassortment between the clades. While FC1 evolved as a single lineage, the FC2 showed a divergent event around 2004 giving rise to two well supported and coexisting sub-lineages, European and Asian. Furthermore, two different spread patterns of EIV in Asian countries were identified. The FC1 outbreaks were caused by independent introductions of EIV from the Americas, being the Asian isolates genetically similar to the contemporary American lineages. On the other hand, the FC2 strains detected in Asian mainland countries conformed an autochthonous monophyletic group with a common ancestor dated in 2006 and showed evidence of an endemic circulation in local host. Characteristic aminoacidic signature patterns were detected in all viral proteins in both Asian-FC1 and FC2 populations. Several changes were located at the top of the HA1 protein, inside or near to antigenic sites. Further studies are needed to assess the potential impact of these antigenic changes in vaccination programs. [ABSTRACT FROM AUTHOR]

Eastern equine encephalitis virus (EEEV) causes a rare but severe disease in horses and humans and is maintained in an enzootic transmission cycle between songbirds and Culiseta melanura mosquitoes. In 2019, the largest EEEV outbreak in the United States for more than 50 years occurred, centered in the Northeast. To explore the dynamics of the outbreak, we sequenced 80 isolates of EEEV and combined them with existing genomic data. We found that, similar to previous years, cases were driven by multiple independent but short-lived virus introductions into the Northeast from Florida. Once in the Northeast, we found that Massachusetts was important for regional spread. We found no evidence of any changes in viral, human, or bird factors which would explain the increase in cases in 2019, although the ecology of EEEV is complex and further data is required to explore these in more detail. By using detailed mosquito surveillance data collected by Massachusetts and Connecticut, however, we found that the abundance of Cs. melanura was exceptionally high in 2019, as was the EEEV infection rate. We employed these mosquito data to build a negative binomial regression model and applied it to estimate early season risks of human or horse cases. We found that the month of first detection of EEEV in mosquito surveillance data and vector index (abundance multiplied by infection rate) were predictive of cases later in the season. We therefore highlight the importance of mosquito surveillance programs as an integral part of public health and disease control. • Genomic sequencing from a large outbreak of EEEV in the Northeast US in 2019 • Outbreak caused by several independent, short-lived virus introductions from Florida • Mosquito abundance and infection rate are predictive of human and horse cases • High-quality mosquito surveillance is vital for controlling outbreaks Hill et al. investigate the drivers behind outbreaks of eastern equine encephalitis virus in the Northeast US, including a large one in 2019. Using virus genome sequencing and mosquito surveillance data, they show it was caused by several small virus introductions from Florida and could be predicted by mosquito abundance and infection rates. [ABSTRACT FROM AUTHOR]

Equine influenza virus strains of Florida sublineage clade 1 (Fc1) have been circulating in North America. In this study, virus neutralization assays were performed to evaluate antigenic differences between Fc1 vaccine strains and North American Fc1 strains isolated in 2021-2022, using equine antisera against A/equine/South Africa/4/2003 (a vaccine strain recommended by the World Organisation for Animal Health) and A/equine/Ibaraki/1/2007 (a Japanese vaccine strain). Antibody titers against four North American Fc1 strains isolated in 2021-2022 were comparable to those against the homologous vaccine strains. These results suggest that current Fc1 vaccine strains are effective against North American strains from 2021-2022., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Purpose The purpose of this investigation was to identify potential environmental risk factors for the diagnosis of equine deep stromal abscesses ( DSA) in the subtropical climate at the University of Florida Veterinary Medical Center ( UFVMC). Methods Cases included were selected from the UFVMC medical record and imaging database, and included all cases of equine DSA diagnosed during the period from December 1991 to December 2013 in patients residing in north central Florida. Patient date of diagnosis and atmospheric data was obtained for north central Florida for the corresponding time period. Univariate and multivariate general linear models were generated testing effects and interactions between environmental conditions. Results When year, sulfur dioxide ( SO2) and wind were analyzed in the presence of each other, a one-mile per hour increase in wind ( P = 0.005) significantly increased the number of DSA cases by 1.63 cases per year. When the influence of temperature was evaluated in conjunction with year and nitrogen dioxide ( NO2), the number of cases decreased by 0.1534 per year for every degree increase in temperature (°C) ( P = 0.039). Conclusions Wind speed is the first significant atmospheric risk factor to be identified for DSA formation in the horse. The importance of environmental variance in the incidence of DSA indicates that the pathogenesis of DSA formation may be multifactorial, interdependent and provides support in some horses for the micropuncture hypothesis of DSA formation related to the involvement of environmental conditions causing precorneal tear film and epithelial damage. [ABSTRACT FROM AUTHOR]

Abstract: A GIS-based risk index model was developed to quantify EEEV transmission risk to horses in the State of Florida. EEEV is a highly pathogenic arbovirus that is endemic along the east coast of the United States, and it is generally fatal to both horses and humans. The model evaluates EEEV transmission risk at individual raster cells in map on a continuous scale of 0–1. The risk index is derived based on local habitat features and the composition and configuration of surrounding land cover types associated with EEEV transmission. The model was verified and validated using the locations of documented horse cases of EEEV. These results of the verification and validation indicate that the model is able to predict locations of EEEV transmission to horses broadly across the state. The model is relatively robust to regional variation in EEEV transmission and habitat conditions in Florida, and it accurately predicted nearly all verification and validation cases in the Panhandle, North, and Central regions of the state. The model performed less accurately in the South, where relatively few cases are documented. Despite these differences, the model provides a useful way to assess EEEV risk both from a regional perspective and at more localized scales. The resulting predictive maps are designed to guide EEEV surveillance and prevention efforts by county mosquito control districts. [Copyright &y& Elsevier]

The objective of this study was to examine the extrinsic risk factors of West Nile virus (WNV) clinical disease in Florida horses as established from confirmed and negative horses tested within the state from 2001 to 2003. An Arboviral Case Information Form (ACF) was submitted by a referring veterinarian at the time of testing to the Florida Department of Agriculture and Consumer Services on every horse suspected of a viral encephalitis in Florida. A follow-up survey that focused on arbovirus prevention and farm ecology was created and mailed to the owner of each tested horse. Data from the follow-up survey indicated peak WNV prevalence in the late summer months in Florida. Quarter horses were the most commonly affected breed. The WNV vaccine was highly protective and natural water on the property also had a protective association. Factors that increased the risk of WNV to horses were the use of fans and a stable construction of solid wood or cement. Some risk indicators were dead birds on the property and other ill animals on the property. Data from this retrospective study have helped identify factors associated with WNV transmission in equines in Florida. Horses that have not been vaccinated and show clinical signs of arboviral infection from June to November should be tested for WNV. Horses that have been vaccinated and show clinical signs should be tested when the vaccination was administered within 1 month or greater than 6 months prior to the onset of clinical symptoms associated with WN infection. [ABSTRACT FROM AUTHOR]

Equine influenza virus (EIV) is a major cause of respiratory disease in horses. Vaccination is an effective tool for infection control. Although various EIV vaccines are widely available, major outbreaks occurred in Europe in 2018 involving a new EIV H3N8 FC1 strain. In France, it was reported that both unvaccinated and vaccinated horses were affected despite >80% vaccination coverage and most horses being vaccinated with a vaccine expressing FC1 antigen. This study assessed whether vaccine type, next to antigenic difference between vaccine and field strain, plays a role. Horses were vaccinated with an ISCOMatrix-adjuvanted, whole inactivated virus vaccine (Equilis Prequenza) and experimentally infected with the new FC1 outbreak strain. Serology (HI), clinical signs, and virus shedding were evaluated in vaccinated compared to unvaccinated horses. Results showed a significant reduction in clinical signs and a lack of virus shedding in vaccinated horses compared to unvaccinated controls. From these results, it can be concluded that Equilis Prequenza provides a high level of protection to challenge with the new FC1 outbreak strain. This suggests that, apart from antigenic differences between vaccine and field strain, other aspects of the vaccine may also play an important role in determining field efficacy. [ABSTRACT FROM AUTHOR]

Equine influenza is a major respiratory disease of horses that is largely controlled by vaccination in some equine populations. Virus-neutralising antibodies, the mainstay of the protective immune response, are problematic in assaying for equine influenza virus, as most strains do not replicate efficiently in cell culture. Surrogate measures of protective antibody responses include the haemagglutination inhibition (HI) test and single radial haemolysis (SRH) assay. For this study, a pseudotyped virus, bearing an envelope containing the haemagglutinin (HA) from the Florida clade 2 equine influenza virus strain A/equine/Richmond/1/07 (H3N8), was generated to measure HA-specific neutralising antibodies in serum samples (n = 134) from vaccinated or experimentally-infected ponies using a pseudotyped virus neutralization test (PVNT). Overall, the results of PVNT were in good agreement with results from the SRH assay (100% sensitivity, 68.53% specificity) and HI test (99.2% sensitivity, 49.03% specificity). The PVNT was apparently more sensitive than either the SRH assay or the HI test, which could be advantageous for studying the antibody kinetics, particularly when antibody levels are low. Nevertheless, further studies are required to determine whether a protective antibody level can be defined for the SRH assay and to ascertain the inter-laboratory reproducibility. In conclusion, the PVNT efficiently measures neutralising antibodies after immunization and/or experimental infection in the natural host, and may complement existing antibody assays. [ABSTRACT FROM AUTHOR]

Although the equine lentivirus (equine infectious anemia virus [EIAV]) poses a major threat to equid populations throughout most regions of the world, detailed knowledge concerning its molecular epidemiology is still in its infancy. Such information is important because the few studies conducted to date suggest there is extensive genetic variation between viral isolates that if confirmed has significant implications for future vaccine design and development of newer diagnostic procedures. Here, we avoid potential assembly artifacts inherent in composite sequencing techniques by using long-range PCR in conjunction with next-generation sequencing for the rapid molecular characterization of all major open reading frames (ORFs) and known transcription factor binding motifs within the long terminal repeats (LTRs) of four North American EIAV isolates from Pennsylvania (EIAV PA ), Tennessee (EIAV TN ), North Carolina (EIAV NC ), and Florida (EIAV FL ). These were compared with complete published EIAV field strain genomic sequences from Asia (EIAV LIA , EIAV MIY ), Europe (EIAV IRE ), and North America (EIAV WY ) plus EIAV UK a laboratory variant of EIAV WY . Phylogenetic analysis using the long-range PCR products suggested all the New World EIAV isolates comprised a single monophyletic group associated with EIAV IRE . This is distinct from the Asian isolates and so consistent with known historical details concerning the reintroduction of equids into North America by European settlers. Nonetheless nucleotide sequence identity for example between EIAV PA and EIAV TN , EIAV NC , EIAV FL , EIAV WY , EIAV UK plus EIAV IRE was limited to 84.6%, 81.0%, 82.1%, 80.4%, 80.1%, and 77.6%, respectively, with some of these values being not too dissimilar to those between EIAV PA and EIAV LIA or EIAV MIY at 78.0% and 75.4%, respectively. Overall, these results suggest substantial genetic diversity exists even within North American EIAV isolates. Comparative alignment of predicted amino acid sequences from all strains provides increased understanding concerning the extent of permitted substitutions in each viral ORF and known transcriptional LTR control elements., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Genetic testing offers precise and accurate data to horse owners concerning their horse's health and offers potential economic value increases of foal crops via genome-assisted selection. Despite availability of at least 96 commercially available markers, fewer than 20 are commonly used. This project seeks to identify the barriers to the incorporation of genomic tools in diverse equine operations. Based on studies examining public opinion of human medical testing, we expected that lack of genetic education and few industry requirements for testing may contribute to neutral or negative opinions regarding genomic tools for horses. We developed a 20 total question survey to capture demographic information such as facility size, type, and primary breed, as well as horse owner familiarity, use, and outlook regarding equine genetic testing. Question types included multiple choice, Likert-type scale, and open-ended response. Recruitment through county extension agents and breed organizations supplied a broad sampling of the Florida horse industry. Responses were collected from February through May 2019. Data showed that 25% of horse owners had genetically tested their horses (n = 60). Of these consumers, 80% rated the quality of their experience as "excellent" or "good" (n = 15). There was a significant positive association between genetic education and likelihood to genetically test. Most respondents (65%) were interested in receiving information regarding genetic testing. Study participants preferred to find materials on genetic testing through Web-based articles and veterinarians. Results of this study will provide researchers with critical knowledge of their audience's needs and a roadmap to tailor future educational resources., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The article presents abstracts on veterinary medicine research topics which include one on the use of a modified Vinsot technique for partial phallectomy in horses, one on the severity of iatrogenic lesions between conventional and modified approaches in 16 equine cadaver forelimbs, and one on the factors associated with anhidrosis in horses in Florida.