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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. [ABSTRACT FROM AUTHOR]

Simple Summary: The association between poor performance and respiratory disease in Thoroughbred racehorses that do not have a structural abnormality of the respiratory tract is often based on anecdotal evidence. We examined peer reviewed publications to determine if there was scientific evidence to link conditions such as inflammation of the airways, asthma, tracheal mucous, and exercise-induced pulmonary haemorrhage (EIPH) with decreased athletic performance. This is a complex field and studies have yielded conflicting results as to the impact of such conditions on performance. For example, some investigators found a significant association between poor racing performance and low-grade EIPH and mild to moderate asthma. In contrast, others have suggested that they may represent a normal response to training and the stabling environment. The key outcome of the review was that there is a dearth of studies unequivocally linking non-structural airway disease with poor performance, and there is a lack of an internationally harmonised approach to the assessment of racehorse performance. Improved investigations providing better quality evidence would facilitate comparison across studies, increase our understanding of the conditions associated with poor performance, safeguard horse welfare, and assist trainers to achieve their goals. The association between poor performance and respiratory disease in Thoroughbred racehorses that do not have a structural abnormality of the respiratory tract, is often based on anecdotal evidence. The objective of this scoping review was to examine the scientific evidence for such associations. Publications were selected based on a search of three databases (PubMed, Scopus, and CAB Direct), in English and without date restriction, followed by a screening process to exclude non-relevant papers, duplicates, and reviews. This process identified 996 publications of which 20 were analysed using the Quality in Prognosis Studies (QUIPS) tool. The results indicated that the evidence supporting the relationship between proposed diagnostic indicators and poor performance is variable. There is a need for better quality evidence. In particular, there are conflicting reports relating to the impact of equine asthma and EIPH on athletic performance. Furthermore, a lack of standardisation in the measurement of racehorse performance makes it difficult to compare findings from different studies. The industry would benefit from high-level guidance concerning the design of controlled performance studies in Thoroughbred racehorses to collect comprehensive data and facilitate targeted interventions. [ABSTRACT FROM AUTHOR]

Since November 2018, several countries in West and Central Africa have reported mortalities in donkeys and horses. Specifically, more than 66,000 horses and donkeys have succumbed to disease in Burkina Faso, Chad, Cameroon, The Gambia, Ghana, Mali, Niger, Nigeria, and Senegal. Strangles caused by Streptococcus equi subsp equi, African Horse Sickness (AHS) virus, and Equine influenza virus (EIV) were all suspected as potential causative agents. This study reports the identification of EIV in field samples collected in Niger and Senegal. Phylogenetic analysis of the hemagglutinin and neuraminidase genes revealed that the identified viruses belonged to clade 1 of the Florida sublineage and were very similar to viruses identified in Nigeria in 2019. Interestingly, they were also more similar to EIVs from recent outbreaks in South America than to those in Europe and the USA. This is one of the first reports providing detailed description and characterization of EIVs in West and Central Africa region. [ABSTRACT FROM AUTHOR]

This study compared concurrent and separate primary vaccination against equid alphaherpesviruses 1 and 4, genus Varicellovirus, subfamily Alphaherpesvirinae, family Herpesviridae, and equine influenza A virus, genus Alphainfluenzavirus, family Orthomyxoviridae. Their vernacular names are equine herpesvirus 1 and 4 (EHV1/4) and equine influenza virus (EIV). Infection with these respiratory pathogens is associated with loss of performance, interruption of training schedules, and on occasion, cancellation of equestrian events. Vaccination is highly recommended, and for some activities it is a mandatory requirement of the relevant authority. As there is a dearth of information relating to the impact of concurrent vaccination on the antibody response to EHV and EIV vaccines, they are usually administered separately, often 2 weeks apart. In a previous study of booster vaccination in Thoroughbred racehorses, concurrent vaccination with whole-virus inactivated carbopol-adjuvanted EHV and EIV vaccines did not impact negatively on the antibody response. In this study, investigations were extended to concurrent versus separate primary vaccination of warmblood foals. A field study was conducted to compare the immune response to a carbopol-adjuvanted EHV vaccine and an immune stimulating complex (ISCOM)-adjuvanted EI vaccine administered concurrently and 2 weeks apart. No adverse clinical reactions were observed, the pattern of EI and EHV antibody response was similar for both groups, and there was no evidence that concurrent primary vaccination compromised the humoral response. The results are of relevance to horse owners who wish to decrease veterinary costs, limit handling of young animals, and simplify record keeping by vaccinating concurrently. [ABSTRACT FROM AUTHOR]

Background: Equine influenza (EI) outbreaks occurred among horses on four racing yards (two National Hunt, one Flat, one mixed National Hunt racing/breeding yard) in Ireland within a 4‐week period. Objectives: To carry out a detailed analysis of racing yards affected in order to identify the source of infection and monitor virus spread among a vaccinated population. Study design: Observational field study. Methods: Epidemiological and vaccination data along with repeat clinical samples were collected from 118 horses on four premises. Results: Failure to implement appropriate biosecurity measures following the introduction of new arrivals and the return of horses from equestrian events contributed to disease spread as did the movement of horses within premises. Mixing of racing and non‐racing populations with inadequate vaccination histories also facilitated virus transmission. The index case(s) on all premises was vaccinated in accordance with the Turf Club rules. Vaccine breakdown was observed across all products in 27/80 horses (33.8%) with an up‐to‐date vaccination record. Eighteen of the 27 (66.7%) horses had not received a booster vaccination within the previous 6 months and 10 (37%) horses were due annual booster vaccination at the time of developing clinical signs. Main limitations: The interpretation of laboratory results followed a delay in veterinary intervention. Conclusions: Annual booster vaccination should not be relied on as the sole preventative measure against EI. The findings of this study suggest that increasing the frequency of booster vaccinations may be beneficial particularly in young horses and that synchronised scheduling of vaccination regimes across racing yards may contribute to high‐risk periods for EI virus (EIV) transmission. [ABSTRACT FROM AUTHOR]

Equine influenza virus (EIV) is a common, highly contagious equid respiratory disease. Historically, EIV outbreaks have caused high levels of equine illness and economic damage. Outbreaks have occurred worldwide in the past decade. The risk for EIV infection is not limited to equids; dogs, cats, and humans are susceptible. In addition, equids are at risk from infection with avian influenza viruses, which can increase mortality rates. EIV is spread by direct and indirect contact, and recent epizootics also suggest wind-aided aerosol transmission. Increased international transport and commerce in horses, along with difficulties in controlling EIV with vaccination, could lead to emergent EIV strains and potential global spread. We review the history and epidemiology of EIV infections, describe neglected aspects of EIV surveillance, and discuss the potential for novel EIV strains to cause substantial disease burden and subsequent economic distress. [ABSTRACT FROM AUTHOR]

Quantitation of virions is one of the important indexes in virological studies. To establish a sensitive and rapid quantitative detection method for equine arteritis virus (EAV), an antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) was developed by using two EAV nucleoprotein monoclonal antibodies (mAbs), 2B9 and 2B3, prepared in this study. After condition optimization, mAb 2B9 was used as the capture antibody, and HRP-labeled 2B3 was chosen as the detecting antibody. The AC-ELISA had a good standard curve when viral particles of the Bucyrus EAV strain were used as a reference standard. The detection limit for the Bucyrus EAV strain was 36 PFU, and the method had a good linear relationship between 72-2297 PFU. The AC-ELISA could specifically detect the Bucyrus EAV strain and had no cross-reaction with other equine viruses. The sensitivity of the AC-ELISA was much higher than that of a western blotting assay but lower than that of a real-time PCR method. However, as a quantitative antigen detection method, the sensitivity of the AC-ELISA was approximately 300 times than the western blotting assay. Furthermore, the AC-ELISA assay could be successfully used in quantification of viral content in an in vitro infection assay, such as a one-step growth curve of EAV, as well as in a transfection assay, such as virus rescue from an infectious cDNA clone of EAV. These results show that the AC-ELISA established in this study is a good alternative for antigen detection of EAV, being a simple, convenient and quantitative detection method for EAV antigens. [ABSTRACT FROM AUTHOR]

Background: In 2013, there was an outbreak of acute respiratory disease in racehorses in Turkey. The clinical signs were consistent with equine influenza (EI). Objective: The aim was to confirm the cause of the outbreak and characterise the causal virus. Methods: A pan‐reactive influenza type A real‐time RT‐PCR and a rapid antigen detection kit were used for confirmatory diagnosis of equine influenza virus (EIV). Immunological susceptibility to EIV was examined using single radial haemolysis and ELISA. Antigenic characterisation was completed by haemagglutinin inhibition using a panel of specific ferret antisera. Genetic characterisation was achieved by whole‐genome sequencing using segment‐specific primers with M13 tags. Results: A H3N8 EIV of the Florida clade 2 sublineage (FC2) was confirmed as the causal agent. The index cases were unvaccinated and immunologically susceptible. Phylogenetic analysis of the HA1 and NA genes demonstrated that A/equine/Ankara/1/2013 clustered with the FC2 strains circulating in Europe. Antigenic characterisation confirmed the FC2 classification and demonstrated the absence of significant drift. Whole‐genome sequencing indicated that A/equine/Ankara/1/2013 is most closely related to the viruses described as the 179 group based on the substitution I179V in HA1, for example A/equine/East Renfrewshire/2/2011, A/equine/Cambremer/1/2012 and A/equine/Saone et Loire/1/2015. The greatest diversity was observed in the NS1 segment and the polymerase complex. Conclusions: The first recorded outbreak of EI in Turkey was caused by an FC2 virus closely related to viruses circulating in Europe. Antigenic and genetic characterisation gave no indication that the current OIE recommendations for EI vaccine composition require modification. [ABSTRACT FROM AUTHOR]

Equid herpesvirus 8 (EHV-8), formerly known as asinine herpesvirus 3, is an alphaherpesvirus that is closely related to equid herpesviruses 1 and 9 (EHV-1 and EHV-9). The pathogenesis of EHV-8 is relatively little studied and to date has only been associated with respiratory disease in donkeys in Australia and horses in China. A single EHV-8 genome sequence has been generated for strain Wh in China, but is apparently incomplete and contains frameshifts in two genes. In this study, the complete genome sequences of four EHV-8 strains isolated in Ireland between 2003 and 2015 were determined by Illumina sequencing. Two of these strains were isolated from cases of abortion in horses, and were misdiagnosed initially as EHV-1, and two were isolated from donkeys, one with neurological disease. The four genome sequences are very similar to each other, exhibiting greater than 98.4% nucleotide identity, and their phylogenetic clustering together demonstrated that genomic diversity is not dependent on the host. Comparative genomic analysis revealed 24 of the 76 predicted protein sequences are completely conserved among the Irish EHV-8 strains. Evolutionary comparisons indicate that EHV-8 is phylogenetically closer to EHV-9 than it is to EHV-1. In summary, the first complete genome sequences of EHV-8 isolates from two host species over a twelve year period are reported. The current study suggests that EHV-8 can cause abortion in horses. The potential threat of EHV-8 to the horse industry and the possibility that donkeys may act as reservoirs of infection warrant further investigation. [ABSTRACT FROM AUTHOR]

We previously reported that horse antiserum against the Japanese equine influenza vaccine virus, A/equine/La Plata/1993 ( LP93) exhibited reduced cross-neutralization against some Florida sublineage Clade (Fc) 2 viruses, for example, A/equine/Carlow/2011 ( CL11). As a result, Japanese vaccine manufacturers will replace LP93 with A/equine/Yokohama/aq13/2010 (Y10, Fc2). To assess the benefit of updating the vaccine, five horses vaccinated with inactivated Y10 vaccine and five vaccinated with inactivated LP93 were challenged by exposure to a nebulized aerosol of CL11. The durations of pyrexia (≥38.5°C) and other adverse clinical symptoms experienced by the Y10 group were significantly shorter than those of the LP93 group. [ABSTRACT FROM AUTHOR]

Background There is a lack of information concerning concurrent administration of vaccines against equine influenza virus ( EIV) and equine herpesvirus 1 and 4 ( EHV-1/4). Objectives The primary objective of this study was to determine the impact of the concurrent use of EIV and EHV-1/4 vaccines in Thoroughbred racehorses on their humoral immune response to EIV. Methods This study was carried out on a population of 30 horses using an inactivated whole-virus EIV vaccine and an inactivated EHV-1/4 vaccine. Horses were randomly allocated to vaccination group A or B. Horses in group A were vaccinated against EIV and EHV-1/4 2 weeks apart. Horses in group B were vaccinated against EIV and EHV-1/4 on the same day. Whole-blood samples were collected on the day of vaccination and 2 weeks and 6 weeks post-vaccination. Antibody levels against EIV and EHV-1/4 were measured using the single radial haemolysis and serum neutralisation test, respectively. Results The pattern of EIV antibody response post-vaccination was similar for both groups. Highest EIV antibody levels were recorded 2 weeks post-vaccination, and a significant decrease in antibody level was observed 4 weeks later. Horses in group B demonstrated a significantly higher EIV antibody response post-vaccination. Overall, there was no significant difference in EHV-1/4 antibody response between the two groups post-vaccination. Conclusion In this study, concurrent vaccination against EIV and EHV-1/4 increased the response to EIV and did not compromise the humoral immune response to EHV-1/4. [ABSTRACT FROM AUTHOR]

Background Equine influenza ( EI) is a highly contagious disease caused by viruses of the H3N8 subtype. The rapid diagnosis of EI is essential to reduce the disease spread. Many rapid antigen detection ( RAD) tests for diagnosing human influenza are available, but their ability to diagnose EI has not been systematically evaluated. Objectives The aim of this study was to compare the performance of 22 RAD tests in the diagnosis of EI. Methods The 22 RAD tests were performed on fivefold serial dilutions of EI virus to determine their detection limits. The four most sensitive RAD tests (ImmunoAce Flu, BD Flu examan, Quick chaser Flu A, B and ESPLINE Influenza A&B-N) were further evaluated using nasopharyngeal samples collected from experimentally infected and naturally infected horses. The results were compared to those obtained using molecular tests. Results The detection limits of the 22 RAD tests varied hugely. Even the four RAD tests showing the best sensitivity were 125-fold less sensitive than the molecular techniques. The duration of virus detection in the experimentally infected horses was shorter using the RAD tests than using the molecular techniques. The RAD tests detected between 27% and 73% of real-time RT- PCR-positive samples from naturally infected horses. Conclusions The study demonstrated the importance of choosing the right RAD tests as only three of 22 were fit for diagnosing EI. It was also indicated that even RAD tests with the highest sensitivity serve only as an adjunct to molecular tests because of the potential for false-negative results. [ABSTRACT FROM AUTHOR]

Background In 2012, equine influenza (EI) virus was confirmed as the cause of outbreaks of respiratory disease in horses throughout South America. In Uruguay and Argentina, hundreds of vaccinated thoroughbred horses in training and racing facilities were clinically affected. Objective To characterise the EI viruses detected during the outbreak in Uruguay and Argentina. Methods Virus was detected in nasopharyngeal swabs by a panreactive influenza type A real-time RT-PCR. The nucleotide sequence of the HA1 gene was determined and analysed phylogenetically using MEGA 5 software. Amino acid sequences alignments were constructed and virus was antigenically characterised with specific ferret antisera. Paired serum samples were tested by haemagglutination inhibition and single radial haemolysis. Results The diagnosis of EIV was confirmed by real-time RT-PCR, virus isolation and serological testing. The phylogenetic analysis of HA1 gene sequences of 18 EI viruses indicated that all of them belong to clade 1 of the Florida sublineage of the American lineage and are closely related to viruses isolated in the United States in 2012. The HA1 of viruses identified in horses in racing facilities in Maro~nas, Uruguay, and in Palermo, Argentina, displayed 100% amino acid sequence identity and were identical to that of a virus isolated in Dubai in 2012, from vaccinated endurance horses recently imported from Uruguay. Conclusions The surveillance data reported illustrate the international spread of EI viruses and support the recommendations of the OIE expert surveillance panel to include viruses of the Florida sublineage in vaccines. [ABSTRACT FROM AUTHOR]

Equine herpesvirus 1 isolates from a 2021 outbreak of neurologic disease in Europe have a mutation, A713G, in open reading frame 11 not detected in 249 other sequences from equine herpesvirus 1 isolates. This single-nucleotide polymorphism could help identify horses infected with the virus strain linked to this outbreak. [ABSTRACT FROM AUTHOR]

Background Equine influenza ( EI) is a highly contagious respiratory disease of horses. Objectives The aim of this study was to evaluate two rapid antigen detection kits ( Directigen or DFA, and Espline) and a commercial ELISA for the detection of EI nucleoprotein in nasal swabs. Method Nasal swab samples from naturally and experimentally infected horses were used to compare the sensitivity and specificity of these assays to virus isolation ( VI) and real-time RT- PCR. Results If real-time RT- PCR was considered as the gold standard, the sensitivity of the other tests in field samples was 68% ( DFA), 35% ( ELISA), 29% (Espline), and 9% ( VI). These tests had 100% specificity when compared to real-time RT- PCR. A receiver operating characteristic ( ROC) curve indicated that decreasing the cutoff of the ELISA would increase sensitivity with some loss of specificity. In samples from experimentally infected horses, the sensitivity of the tests compared with real-time RT- PCR was 69% ( VI), 27% ( DFA), 6% ( Espline), and 2% ( ELISA). The specificity was 100% for Espline and ELISA and 95% for VI and DFA. Conclusions This study illustrated that DFA is the most sensitive antigen detection test evaluated for the diagnosis of EI and that it can detect virus in some subclinical infected and vaccinated horses. The results suggest that DFA is a useful adjunct to laboratory tests and may be effective as a screening test in a quarantine station or similar facility where horses are monitored daily. [ABSTRACT FROM AUTHOR]

Background Outbreaks of equine influenza ( EI) in endemic populations cause disruption and economic loss. Objectives To identify (i) factors involved in the spread of EI (ii) virus strains responsible for outbreaks (iii) single radial haemolysis ( SRH) antibody levels correlating with protection against current virus strains (iv) evidence of vaccination breakdown. Methods RT- PCR, virus isolation and SRH were carried out on nasopharyngeal swabs and blood samples collected from horses, ponies and donkeys on affected premises. Data relating to 629 samples from 135 equidae were analysed. Results and conclusions Outbreaks were sporadic, self limiting and associated with the movement of horses. Vaccination status and age influenced clinical signs of disease while housing and fomites contributed to virus spread. Subclinical infection as defined as a horse which tested positive by one or more of the following; RT- PCR, virus isolation and seroconversion in the absence of clinical signs, was identified in 9% of animals. Of the horses with up to date vaccination records 32% developed clinical signs. Vaccine breakdown occurred among horses vaccinated with all four commercially available vaccines. Analysis of HA1 sequence data generated for 26 viruses indicated that they all belonged to clade 2 of the Florida sublineage. Higher SRH antibody levels were required for both clinical and virological protection than reported in studies where vaccine strains were antigenically and genetically similar to those circulating in the field. The results of this study therefore support the OIE recommendations that vaccines be updated to include representatives of both clades of the Florida sublineage. [ABSTRACT FROM AUTHOR]

Background Antibodies against equine influenza virus ( EIV) are traditionally quantified by haemagglutination inhibition ( HI) or single radial haemolysis ( SRH). Objectives To evaluate an ELISA for the detection of antibodies against influenza nucleoprotein in the diagnosis and surveillance of equine influenza ( EI). Methods The ELISA was compared with the SRH and HI tests. Serial serum samples from 203 naturally and 14 experimentally infected horses, from 60 weanlings following primary vaccination with five different vaccines (two whole inactivated vaccines, two ISCOM-based subunit vaccines and a recombinant canarypox virus vaccine) and from 44 adult horses following annual booster vaccination with six different vaccines were analysed. Results Fewer seroconversions were detected in clinical samples by ELISA than by SRH or HI but ELISA was more sensitive than SRH in naïve foals post-experimental infection. The ELISA did not detect the antibody response to vaccination with the recombinant canarypox virus vaccine confirming the usefulness of the combination of this kit and vaccine to differentiate between naturally infected and vaccinated horses, that is, DIVA. No DIVA capacity was evident with the other vaccines. Conclusion The results suggest that this ELISA is a useful supplementary test for the diagnosis of EI although less sensitive than HI or SRH. It is an appropriate test for EI surveillance in a naïve population and may be combined with the recombinant canarypox virus vaccine but not with other commercially available subunit vaccines, in a DIVA strategy. [ABSTRACT FROM AUTHOR]

Influenza virus infection remains a public health problem worldwide. The mechanisms underlying viral control during an uncomplicated influenza virus infection are not fully understood. Here, we developed a mathematical model including both innate and adaptive immune responses to study the within-host dynamics of equine influenza virus infection in horses. By comparing modeling predictions with both interferon and viral kinetic data, we examined the relative roles of target cell availability, and innate and adaptive immune responses in controlling the virus. Our results show that the rapid and substantial viral decline (about 2 to 4 logs within 1 day) after the peak can be explained by the killing of infected cells mediated by interferon activated cells, such as natural killer cells, during the innate immune response. After the viral load declines to a lower level, the loss of interferon-induced antiviral effect and an increased availability of target cells due to loss of the antiviral state can explain the observed short phase of viral plateau in which the viral level remains unchanged or even experiences a minor second peak in some animals. An adaptive immune response is needed in our model to explain the eventual viral clearance. This study provides a quantitative understanding of the biological factors that can explain the viral and interferon kinetics during a typical influenza virus infection. INSET: Author Summary. [ABSTRACT FROM AUTHOR]

Please cite this paper as: Cullinane et al. (2010) Equine influenza - surveillance and control. Influenza and Other Respiratory Viruses 4(6), 339-344. Equine influenza virus (EIV) is considered the most important respiratory virus of horses because it is highly contagious and has the potential to disrupt major equestrian events. Equine influenza (EI) can be controlled by vaccination but it has been demonstrated repeatedly in the field that antigenic drift impacts on vaccine efficacy. EI surveillance maintains awareness of emergence and international spread of antigenic variants. It not only serves as an early warning system for horse owners, trainers and veterinary clinicians but is fundamental to influenza control programmes based on vaccination. Data on outbreaks of EI and strain characterisation is reviewed annually by an Expert Surveillance Panel (ESP) including representatives from OIE and WHO. This panel makes recommendations on the need to update vaccines based on analysis of evidence of disease in well vaccinated horses, antigenic changes, genetic changes and when possible, experimental challenge data. However, the disparity in the level of surveillance and virus collection in different countries results in potentially biased information about the relative prevalence of different viruses. There is a need for increased surveillance on a global level and a greater awareness of the benefits of updating the vaccines. The vaccine companies have traditionally been slow to respond to the ESP recommendations. Veterinary clinicians have a major role to play in purchasing vaccines with epidemiologically relevant strains and promoting their benefits to their clients. [ABSTRACT FROM AUTHOR]

Please cite this paper as: Gildea et al. (2010) A comparative antibody study of the potential susceptibility of Thoroughbred and non-Thoroughbred horse populations in Ireland to equine influenza virus. Influenza and Other Respiratory Viruses 4(6), 363-372. In Ireland, horses may be protected against equine influenza virus (EIV) as a result of natural exposure or vaccination. Current mandatory vaccination programmes are targeted at highly mobile horses. A correlation between antibody levels as measured by single radial haemolysis (SRH) and protective immunity against EIV has been established. The objective of this study was to determine the susceptibility of selected populations of horses by quantifying their antibodies to EIV. Blood samples were collected from Thoroughbred weanlings, yearlings, racehorses and broodmares, teaser stallions and non-Thoroughbred horses. Antibodies against EIV H3N8 and H7N7 were measured by SRH. The order of susceptibility to Equine Influenza (EI) in the populations examined in Ireland was as follows: Thoroughbred weanlings > teasers > non-Thoroughbred horses and ponies > Thoroughbred yearlings > Thoroughbred horses in training > Thoroughbred broodmares. The H3N8 antibody levels of the weanlings, yearlings, broodmares and horses in training were similar to their H7N7 antibody levels, suggesting that their antibodies were primarily vaccinal in origin. The teasers and non-Thoroughbreds had higher H3N8 antibody levels than H7N7 antibody levels, suggesting that the majority of seropositive horses in these populations had been exposed to H3N8 by natural infection. Weanlings, teasers and non-Thoroughbred horses were identified as most susceptible to EIV. The results suggest that it would be advisable that weanlings are vaccinated prior to attendance at public sales, that teaser stallions are vaccinated prior to each breeding season and that mandatory vaccination be implemented for participation in non-Thoroughbred events. [ABSTRACT FROM AUTHOR]

Objective: To characterize a monoclonal IgGκ (MAb) from a patient with planar xanthoma that precipitated with serum lipids at reduced temperature. Methods: The molecular weight (Mr), sensitivity to proteases, and glycosylation of the purified MAb were analyzed. The specificity of the MAb was tested by measuring cryoprecipitation with pure high- (HDL) and low-density (LDL) lipoproteins. The effect of choline, phosphocholine, and glycerol 3-phosphate on the precipitation temperature of LDL by the MAb was studied. Results: The MAb was larger than normal IgG due to hyperglycosylation of the MAb light chain. It formed cryoprecipitates with pure HDL and LDL as well as the lipids extracted from these lipoproteins. Fab fragments of the MAb lowered the temperature of its precipitation with LDL. Choline, phosphocholine, and glycerol 3-phosphate also lower the precipitation temperature. Conclusion: This is the first human IgG reported with apparent specificity for phosphocholine antigens. Its precipitation with lipids at reduced temperature suggests that it recognizes conformations of phospholipid head groups that develop below core body temperature. [ABSTRACT FROM AUTHOR]

We have developed an assay of thrombin generation in clotting whole blood. Because our goal was to study patients with red blood cell diseases that are associated with thrombosis, the initial evaluation of this assay analysed the effect of the haematocrit and haemolysate on the total amount of thrombin activity generated and the maximal concentration of thrombin achieved. Both of these parameters were proportional to the haematocrit throughout a wide range of clinically relevant cell concentrations. Red cell lysate also augmented thrombin generation. Because this effect was removed by filtration of the lysate, we propose that it was related to red cell microparticles. [ABSTRACT FROM AUTHOR]

A library of the equine herpesvirus 4 (EHV-4) genome was constructed in the λgt11 expression vector. Recombinant bacteriophage expressing EHV-4 antigens as beta-galactosidase fusion proteins were detected with rabbit antiserum raised against EHV-4 virions and convalescent horse serum. EHV-4 DNA sequences contained in the immunopositive recombinants were used as hybridization probes for mapping the genes encoding the antigens on the viral genome. The DNA sequence of the probes was determined. Screening the library with rabbit antiserum led to the identification of 40 recombinants, 26 of which were further characterized. Determination of the DNA sequence of the EHV-4 inserts revealed that 23 of the recombinants encode an identical portion of glycoprotein gB. Two of the recombinants encode a portion of the previously unidentified EHV-4 homologue of the EHV-1 immediate early protein. The EHV-4 insert of the remaining recombinant encodes a portion of the previously unidentified EHV-4 homologue of herpes simplex virus 1 (HSV-1) UL36, a tegument protein. Screening the library horse serum led to the identification of three recombinants, one of which encodes the same gB sequence as the gB recombinant recognized with the rabbit serum. The other two contain overlapping sequences that encode a portion of EHV-4 gX. [ABSTRACT FROM AUTHOR]

The international governing body of equestrian sports requires that horses be vaccinated against equine influenza within 6 months and 21 days of competing. The aim of this study was to compare the antibody response of young sport horses to six-monthly booster vaccination with equine influenza vaccines of different formulations. An inactivated vaccine was allocated to 35 horses and subunit and recombinant vaccines were allocated to 34 horses each. After vaccination, all horses were monitored for evidence of adverse reactions. Whole blood samples were collected at the time of vaccination and on nine occasions up to six months and 21 days post vaccination. Antibodies against equine influenza were measured by single radial haemolysis. Transient fever and injection site reactions were observed in several horses vaccinated with each vaccine. Only two horses failed to seroconvert post booster vaccination but there was a delayed response to the recombinant vaccine. The antibody response to the recombinant vaccine was lower than that induced by the whole-inactivated and subunit vaccines up to three months post vaccination. Thereafter, there was no significant difference. By six months post vaccination, the majority of horses in all three groups were clinically but not virologically protected. There was minimal decline in antibody titres within the 21-day grace period. [ABSTRACT FROM AUTHOR]

To facilitate the temporary importation of horses for competition and racing purposes, with a minimum risk of transmitting equine influenza, the World Organisation for Animal Health (Office International des Epizooties, or OIE), formally engaged in a public–private partnership with the Federation Equestre Internationale (FEI) and the International Federation for Horseracing Authorities (IFHA) to establish, within the context of existing OIE standards, a science-based rationale to identify the ideal time period for equine influenza vaccination prior to shipment. Field trials using vaccines based on different technologies were carried out on three continents. The antibody response post-booster vaccination at intervals aligned with the different rules/recommendations of the OIE, FEI, and IFHA, was monitored by single radial haemolysis. It was determined that 14 days was the optimum period necessary to allow horses adequate time to respond to booster vaccination and for horses that have previously received four or more doses of vaccine and are older than four years, it is adequate to allow vaccination within 180 days of shipment. In contrast, the results indicate that there is a potential benefit to younger (four years old or younger) horses in requiring booster vaccination within 90 days of shipment, consistent with the current OIE standard. [ABSTRACT FROM AUTHOR]

Cancer patients with venous access devices (VADs) often receive daily flushes of heparin. Even this relatively small heparin exposure has been reported to induce immune-mediated thrombocytopenia. To estimate how frequently this occurs we tested for heparin-related antibodies in 49 patients receiving daily heparin flushes of their VADs. Although one-third of the patients showed evidence of heparin sensitization on at least one occasion during their surveillance, their antibody titers were generally low and typical of those found in other cohorts of patients who become sensitized to heparin but do not develop secondary thrombocytopenia. However, one patient developed a positive serotonin release assay indicative of a more significant sensitization, but without thrombocytopenia. Therefore, our observations suggest that heparin-induced thrombocytopenia (HIT) related to heparin flushes of VADs is uncommon but still an important diagnosis to entertain. [ABSTRACT FROM AUTHOR]

The aim of this study was to identify respiratory viruses circulating amongst elite racehorses in a training yard by serological testing of serial samples and to determine their impact on health status and ability to race. A six-month longitudinal study was conducted in 30 Thoroughbred racehorses (21 two-year-olds, five three-year-olds and four four-year-olds) during the Flat racing season. Sera were tested for the presence of antibodies against equine herpesvirus 1 and 4 (EHV-1 and EHV-4) and equine rhinitis viruses A and B (ERAV and ERBV) by complement fixation (CF) and equine arteritis virus (EAV) by ELISA. Antibodies against equine influenza (EI) were measured by haemagglutination inhibition (HI). Only ERAV was circulating in the yard throughout the six-month study period. Seroconversion to ERAV frequently correlated with clinical respiratory disease and was significantly associated with subsequent failure to race (p = 0.0009). Over 55% of the two-year-olds in the study seroconverted to ERAV in May and June. In contrast, only one seroconversion to ERAV was observed in the older horses. They remained free of any signs of respiratory disease and raced successfully throughout the study period. The importance of ERAV as a contributory factor in the interruption of training programmes for young horses may be underestimated. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the presence of equine coronavirus (ECoV) in clinical samples submitted to a diagnostic laboratory in Ireland. A total of 424 clinical samples were examined from equids with enteric disease in 24 Irish counties between 2011 and 2015. A real-time reverse transcription polymerase chain reaction was used to detect ECoV RNA. Nucleocapsid, spike and the region from the p4.7 to p12.7 genes of positive samples were sequenced, and sequence and phylogenetic analyses were conducted. Five samples (1.2%) collected in 2011 and 2013 tested positive for ECoV. Positive samples were collected from adult horses, Thoroughbred foals and a donkey foal. Sequence and/or phylogenetic analysis showed that nucleocapsid, spike and p12.7 genes were highly conserved and were closely related to ECoVs identified in other countries. In contrast, the region from p4.7 and the non-coding region following the p4.7 gene had deletions or insertions. The differences in the p4.7 region between the Irish ECoVs and other ECoVs indicated that the Irish viruses were distinguishable from those circulating in other countries. This is the first report of ECoV detected in both foals and adult horses in Ireland. [ABSTRACT FROM AUTHOR]

Equine herpesvirus 1 (EHV-1) is an Alphaherpesvirus infecting not only horses but also other equid and non-equid mammals. It can cause respiratory distress, stillbirth and neonatal death, abortion, and neurological disease. The different forms of disease induced by EHV-1 infection can have dramatic consequences on the equine industry, and thus the virus represents a great challenge for the equine and scientific community. This report describes the progress of a major EHV-1 outbreak that took place in Normandy in 2009, during which the three forms of disease were observed. A collection of EHV-1 strains isolated in France and Belgium from 2012 to 2018 were subsequently genetically analysed in order to characterise EHV-1 strain circulation. The open reading frame 30 (ORF30) non-neuropathogenic associated mutation A2254 was the most represented among 148 samples analysed in this study. ORF30 was also sequenced for 14 strains and compared to previously published sequences. Finally, a more global phylogenetic approach was performed based on a recently described Multilocus Sequence Typing (MLST) method. French and Belgian strains were clustered with known strains isolated in United Kingdom and Ireland, with no correlation between the phylogeny and the time of collection or location. This new MLST approach could be a tool to help understand epidemics in stud farms. [ABSTRACT FROM AUTHOR]

In August 2015, Malaysia experienced an outbreak of acute respiratory disease in racehorses. Clinical signs observed were consistent with equine influenza (EI) infection. The index cases were horses recently imported from New Zealand. Rapid control measures, including temporary cancellation of racing, were implemented to minimize the impact of the outbreak. By November, the disease outbreak was resolved, and movement restrictions were lifted. The aim of this study was to confirm the clinical diagnosis and characterize the causal virus. A pan-reactive influenza type A real-time RT-PCR was used for confirmatory diagnosis. Antigenic characterization by haemagglutinin inhibition using a panel of specific ferret antisera indicated that the causal virus belonged to clade 1 of the H3N8 Florida sub-lineage. The genetic characterization was achieved by the whole genome sequencing of positive nasal swabs from clinically affected animals. Pylogenetic analysis of the haemagglutinin (HA) and neuraminidase (NA) genes demonstrated ≥99% homology with several EI strains that had recently circulated in the USA and Japan. The antigenic and genetic characterization did not indicate that the current World Organisation for Animal Health (OIE) recommendations for EI vaccine composition required modification. [ABSTRACT FROM AUTHOR]

Multiple locus typing based on sequencing heterologous regions in 26 open reading frames (ORFs) of equine herpesvirus 1 (EHV-1) strains Ab4 and V592 was used to characterise 272 EHV-1 isolates from 238 outbreaks of abortion, respiratory or neurological disease over a 28-year period. The analysis grouped the 272 viruses into at least 10 of the 13 unique long region (UL) clades previously recognised. Viruses from the same outbreak had identical multi-locus profiles. Sequencing of the ORF68 region of EHV-1 isolates from 222 outbreaks established a divergence into seven groups and network analysis demonstrated that Irish genotypes were not geographically restricted but clustered with viruses from all over the world. Multi-locus analysis proved a more comprehensive method of strain typing than ORF68 sequencing. It was demonstrated that when interpreted in combination with epidemiological data, this type of analysis has a potential role in tracking virus between premises and therefore in the implementation of targeted control measures. Viruses from 31 of 238 outbreaks analysed had the proposed ORF30 G2254/D752 neuropathogenic marker. There was a statistically significant association between viruses of the G2254/D752 genotype and both neurological disease and hypervirulence as defined by outbreaks involving multiple abortion or neurological cases. The association of neurological disease in those with the G2254/D752 genotype was estimated as 27 times greater than in those with the A2254/N752 genotype. [ABSTRACT FROM AUTHOR]

Equine influenza (EI) outbreaks occurred on 19 premises in Ireland during 2014. Disease affected thoroughbred (TB) and non-TB horses/ponies on a variety of premises including four racing yards. Initial clinical signs presented on 16 premises within a two-month period. Extensive field investigations were undertaken, and the diagnostic effectiveness of a TaqMan RT-PCR assay was demonstrated in regularly-vaccinated and sub-clinically-affected horses. Epidemiological data and repeat clinical samples were collected from 305 horses, of which 40% were reported as clinically affected, 39% were identified as confirmed cases and 11% were sub-clinically affected. Multivariable analysis demonstrated a significant association between clinical signs and age, vaccination status and number of vaccine doses received. Vaccine breakdown was identified in 31% of horses with up to date vaccination records. This included 27 horses in four different racing yards. Genetic and antigenic analysis identified causal viruses as belonging to Clade 2 of the Florida sublineage (FCL2). At the time of this study, no commercially available EI vaccine in Ireland had been updated in line with World Organisation for Animal Health (OIE) recommendations to include a FCL2 virus. The findings of this study highlight the potential ease with which EI can spread among partially immune equine populations. [ABSTRACT FROM AUTHOR]