H3N8 is an influenza virus subtype that affects horses, resulting in equine influenza, a highly contagious respiratory disease. This virus is characterized by its ability to spread rapidly among equine populations, leading to symptoms such as fever, coughing, nasal discharge, and reduced performance. H3N8 is part of the Orthomyxoviridae family and is known for its potential to mutate, which can complicate control and prevention efforts. Vaccination is a common preventive measure, and biosecurity practices are employed to limit transmission. This page compiles peer-reviewed research studies and scholarly articles that explore the virology, epidemiology, and impact of H3N8 on equine health, including vaccine development and outbreak management strategies.
Paillot R, Prowse L, Donald C, Medcalf E, Montesso F, Bryant N, Watson J, Jeggo M, Elton D, Newton R, Trail P, Barnes H.An outbreak of H3N8 Equine Influenza virus (EIV) that occurred in vaccinated horses in Japan was caused by a genetically divergent EIV isolate of the Florida clade 1 sub-lineage. This virus subsequently entered Australia where it infected thousands of immunologically naïve horses. The objective of this study was to evaluate the ability of a non-updated whole inactivated equine influenza (EI) vaccine to protect if used in the face of an outbreak induced by a virus similar to the ones circulating in Japan and Australia in 2007. Seven naïve Welsh mountain ponies were immunised twice with the co...
Nishiura H, Satou K.An outbreak of equine influenza (H3N8) occurred among fully vaccinated racehorses in Japan from August to September, 2007. To assess the potential effectiveness of public health interventions other than vaccination (i.e. movement restriction, isolation and quarantine), which started immediately on the date of detection of the first febrile case, a simple epidemiological model was developed and applied to the observed data. The epidemic curves in five racehorse facilities revealed consistent temporal patterns: (i) a sharp increase in symptom onset of cases during the first 3 days, which is thou...
Qi T, Guo W, Huang W, Dai L, Zhao L, Li H, Li X, Zhang X, Wang Y, Yan Y, He N, Xiang W.During the 2007 outbreak of equine influenza (EIV) in China, an influenza virus designated A/donkey/Xinjiang/5/2007 (donkey/Xinjiang/2007) was isolated from a symptomatic donkey in Xinjiang Uygur Autonomous Region, China. To analyze the genetic evolution of the new isolate, the hemagglutinin (HA) gene of donkey/Xinjiang/2007 was amplified and sequenced. Sequence alignment, prediction of glycosylation sites and phylogenetic analysis of the HA1 protein of donkey/Xinjiang/2007 showed most similarity to the Florida sublineage clade 2 of the American lineage of equine influenza viruses. The HA1 seq...
Virmani N, Bera BC, Singh BK, Shanmugasundaram K, Gulati BR, Barua S, Vaid RK, Gupta AK, Singh RK.An outbreak of equine influenza (EI) was reported in India in June, 2008 after a gap of two decades. The outbreak started from Jammu and Kashmir (Katra), northern state of India and spread to the other parts of the country affecting equines in 11 states. The virus (H3N8) was isolated from nasal swabs obtained from clinical cases in various locations in the country including Katra (Jammu and Kashmir), Mysore (Karnataka) and Ahmedabad (Gujarat) using embryonated chicken eggs. The virus isolates were identified as H3N8 by haemagglutination inhibition (HI) test titration with standard serum and by...
Soboll G, Hussey SB, Minke JM, Landolt GA, Hunter JS, Jagannatha S, Lunn DP.Equine influenza virus remains an important problem in horses despite extensive use of vaccination. Efficacy of equine influenza vaccination depends on the onset and duration of protective immunity, and appropriate strain specificity of the immune response. This study was designed to test the protective immunity resulting from vaccination with the North American commercial ALVAC equine influenza vaccine (RECOMBITEK Influenza, Merial, USA)(1) against challenge with American lineage influenza viruses. In experiment 1, 12 ponies were vaccinated twice, at a 35 day interval, using the ALVAC-influen...
Lu Z, Chambers TM, Boliar S, Branscum AJ, Sturgill TL, Timoney PJ, Reedy SE, Tudor LR, Dubovi EJ, Vickers ML, Sells S, Balasuriya UB.The objective of this study was to develop and evaluate new TaqMan real-time reverse transcription-PCR (rRT-PCR) assays by the use of the minor groove binding probe to detect a wide range of equine influenza virus (EIV) strains comprising both subtypes of the virus (H3N8 and H7N7). A total of eight rRT-PCR assays were developed, targeting the nucleoprotein (NP), matrix (M), and hemagglutinin (HA) genes of the two EIV subtypes. None of the eight assays cross-reacted with any of the other known equine respiratory viruses. Three rRT-PCR assays (EqFlu NP, M, and HA3) which can detect strains of th...
Yamanaka T, Nemoto M, Tsujimura K, Kondo T, Matsumura T.In horse populations, influenza A virus subtype H3N8 (equine influenza virus, EIV) is a very important pathogen that leads to acute respiratory disease. Recently, EIV has emerged in dogs, and has become widespread among the canine population in the United States. The interspecies transmission route had thus far remained unclear. Here, we tested whether the interspecies transmission of EIV to dogs could occur as a result of close contact with experimentally EIV-infected horses. Three pairs consisting of an EIV-infected horse and a healthy dog were kept together in individual stalls for 15 conse...
Bryant NA, Rash AS, Russell CA, Ross J, Cooke A, Bowman S, MacRae S, Lewis NS, Paillot R, Zanoni R, Meier H, Griffiths LA, Daly JM, Tiwari A....Equine influenza virus (EIV) surveillance is important in the management of equine influenza. It provides data on circulating and newly emerging strains for vaccine strain selection. To this end, antigenic characterisation by haemaggluttination inhibition (HI) assay and phylogenetic analysis was carried out on 28 EIV strains isolated in North America and Europe during 2006 and 2007. In the UK, 20 viruses were isolated from 28 nasopharyngeal swabs that tested positive by enzyme-linked immunosorbent assay. All except two of the UK viruses were characterised as members of the Florida sublineage w...
Müller I, Pinto E, Santibáñez MC, Celedón MO, Valenzuela PD.The equine influenza virus is the causal agent of influenza in horses. In July 2006, horses from various regions of Chile presented fever, serious nasal discharge, dry cough, anorexia and depression. Here we describe the isolation and characterization of the virus responsible for this outbreak. The virus was identified as equine influenza virus H3N8, since haemagglutination was inhibited by an anti-A/equi/1/H3N8 serum, but not by an anti-A/equi/1/H7N7 serum. The isolate was named A/equi/2/Lonquén/06 (H3N8). In addition, we describe the isolation and sequencing of the haemagglutinin, neuramini...
Foord AJ, Selleck P, Colling A, Klippel J, Middleton D, Heine HG.Equine influenza (EI) virus (H3N8) was identified in the Australian horse population for the first time in August 2007. The principal molecular diagnostic tool used for detection was a TaqMan real-time reverse transcription-polymerase chain reactions (RT-PCR) assay specific for the matrix (MA) gene of influenza virus type A (IVA). As this assay is not specific for EI, we developed a new EI H3-specific TaqMan assay targeting the haemagglutinin (HA) gene of all recent EI H3 strains. The IVA and the EI H3 TaqMan assays were assessed using in vitro transcribed RNA template, virus culture, diagnost...
Ito M, Nagai M, Hayakawa Y, Komae H, Murakami N, Yotsuya S, Asakura S, Sakoda Y, Kida H.In August 2007, an outbreak of equine influenza occurred among vaccinated racehorses with Japanese commercial equine influenza vaccine at Kanazawa Racecourse in Ishikawa prefecture in Japan. Apparent symptoms were pyrexia (38.2-41.0 degrees C) and nasal discharge with or without coughing, although approximately half of the infected horses were subclinical. All horses had been shot with a vaccine that contained two inactivated H3N8 influenza virus strains [A/equine/La Plata/93 (La Plata/93) of American lineage and A/equine/Avesta/93 (Avesta/93) of European lineage] and an H7N7 strain (A/equine/...
Yamanaka T, Niwa H, Tsujimura K, Kondo T, Matsumura T.On August 2007, we encountered equine influenza epidemic by Florida sub-lineage strain (H3N8) in Japan Racing Association's facilities where 4142 racehorses in total were stabled. The number of new febrile cases sharply increased, but the occurrence was rapidly calmed down within 2 weeks. The morbidity rate in these facilities was 12.8% and the subclinical infection rate of healthy racehorses examined by rapid antigen detection tests was 19.4% at the early stage of epidemic. The serological studies along with the low morbidity rate and the existence of numbers of asymptomatically infected race...
Barbic L, Madic J, Turk N, Daly J.In April 2004 an outbreak of equine influenza occurred at the Zagreb hippodrome, Croatia. Clinical respiratory disease of the same intensity was recorded in vaccinated and non-vaccinated horses. The equine influenza vaccine used in Croatia at the time of the outbreak contained the strains A/equine/Miami/63 (H3N8), A/equine/Fontainebleau/79 (H3N8) and A/equine/Prague/56 (H7N7). At the same time, the usual strains in vaccines used in Europe were, in accordance with the recommendation of the World Organisation for Animal Health (OIE) Expert Surveillance Panel on equine influenza, A/equine/Newmark...
Daly J, Daas A, Behr-Gross ME.In 2004, the Office International des Epizooties (OIE) Expert Surveillance Panel on equine influenza recommended that the American lineage component (H3N8) of equine influenza vaccines (A/eq/Newmarket/1/93-like) be updated to an A/eq/South Africa/4/03-like virus. As a consequence the common European Pharmacopoeia (Ph. Eur.) - OIE reference for equine influenza subtype 2 American-like antiserum had to be complemented by an antiserum raised in horses against an A/eq/South Africa/4/03 strain. An international collaborative study run by the European Directorate for the Quality of Medicines (EDQM) ...
Paillot R, Grimmett H, Elton D, Daly JM.In the horse, conventional inactivated or subunit vaccines against equine influenza virus (EIV) induce a short-lived antibody-based immunity to infection. Alternative strategies of vaccination have been subsequently developed to mimic the long-term protection induced by natural infection with the virus. One of these approaches is the use of immune-stimulating complex (ISCOM)-based vaccines. ISCOM vaccines induce a strong antibody response and protection against influenza in horses, humans, and a mouse model. Cell-mediated immunity (CMI) has been demonstrated in humans and mice after ISCOM vacc...
Daly JM, Sindle T, Tearle J, Barquero N, Newton JR, Corning S.Surveillance of equine influenza viruses has suggested that strains included in currently licensed vaccines are a poor match for those predominantly circulating in the field. Objective: To assess the ability of Duvaxyn IE-T Plus to provide cross protection against the newly evolved South Africa/4/03 (H3N8) strain of equine influenza virus. Methods: The vaccine efficacy was evaluated by challenge infection with influenza strain A/eq/South Africa/4/03 (H3N8) 2 weeks after a primary course of 2 vaccinations with Duvaxyn IE-T Plus given at a 4-week interval. The outcome of challenge in vaccinated ...
Minke JM, Toulemonde CE, Dinic S, Cozette V, Cullinane A, Audonnet JC.A classical limitation of early life immunization is the interference by maternally derived antibodies, which are known to inhibit the immune response to modified-live and killed vaccines. Several studies have convincingly shown that even minute amounts of maternally derived antibodies against equine influenza can strongly interfere with successful vaccination of foals born to immune mares. In this study we evaluated the response of foals born to vaccinated mares to immunization with a canarypox-vectored recombinant vaccine against equine influenza virus H3N8. The recombinant vaccine was able ...
Minke JM, Toulemonde CE, Coupier H, Guigal PM, Dinic S, Sindle T, Jessett D, Black L, Bublot M, Pardo MC, Audonnet JC.To determine onset and duration of immunity provided by a 2- or 3-dose series of a new canarypox-vectored recombinant vaccine for equine influenza virus (rCP-EIV vaccine) expressing the hemagglutinin genes of influenza H3N8 virus strains A/eq/Kentucky/94 and A/eq/Newmarket/2/93 in ponies. Methods: Forty-nine 1- to 3-year-old male Welsh Mountain Ponies that were seronegative for equine influenza virus. Methods: Vaccinated and control ponies were challenged with aerosolized influenza virus A/eq/Sussex/89 (H3N8), representative of the Eurasian lineage of circulating influenza viruses. In trial 1,...
Martella V, Elia G, Decaro N, Di Trani L, Lorusso E, Campolo M, Desario C, Parisi A, Cavaliere N, Buonavoglia C.In December 2005, equine influenza virus infection was confirmed as the cause of clinical respiratory disease in vaccinated horses in Apulia, Italy. The infected horses had been vaccinated with a vaccine that contained strains representatives from both the European (A/eq/Suffolk/89) and American (A/eq/Newmarket/1/93) H3N8 influenza virus lineages, and the H7N7 strain A/eq/Praga/56. Genetic characterization of the hemagglutinin (HA) and neuraminidase (NA) genes of the virus from the outbreak, indicated that the isolate (A/eq/Bari/2005) was an H3N8 strain closely related to recent representative...
Yamanaka T, Tsujimura K, Kondo T, Hobo S, Matsumura T.We investigated the efficacy of the oral administration of oseltamivir phosphate (OP) in horses experimentally infected with equine influenza A virus (H3N8). Nine horses were divided into three horses each of control, treatment and prophylaxis groups. An administration protocol for the treatment group (2 mg/kg of body weight, twice a day for five days) was started immediately after the onset of pyrexia (above 38.9 degrees C). An administration protocol for the prophylaxis group (2 mg/kg of body weight, once a day for five days) was started on a day before viral inoculation. In the treatment gr...
Boliar S, Stanislawek W, Chambers TM.The hemagglutination inhibition test is used by many diagnostic and surveillance laboratories for detection of antibodies to influenza viruses. It is well known that the hemagglutination inhibition test is affected by nonspecific inhibitors present in equine serum. Several serum treatments are in use to remove these inhibitors, including treatment with kaolin. Discrepant results were observed in the authors' laboratories when using kaolin treatment before testing equine sera for antibodies against equine influenza virus (EIV) subtype-1 (H7N7). It is demonstrated here that kaolin treatment lead...
Paillot R, Kydd JH, Sindle T, Hannant D, Edlund Toulemonde C, Audonnet JC, Minke JM, Daly JM.In horses, equine influenza virus (EIV) is a leading cause of respiratory disease. Conventional inactivated vaccines induce a short-lived immune response. By comparison, natural infection confers a long-term immunity to re-infection. An aim of new equine influenza vaccines is to more closely mimic natural infection in order to achieve a better quality of immunity. A new live recombinant vaccine derived from the canarypox virus vector and expressing haemagglutinin genes of EIV (subtype H3N8) has been developed. Stimulation of the immune system was studied after immunisation with this canarypox-...
Newton JR, Daly JM, Spencer L, Mumford JA.Between March and May 2003, equine influenza virus infection was confirmed as the cause of clinical respiratory disease among both vaccinated and unvaccinated horses of different breeds and types in at least 12 locations in the UK. In the largest outbreak, 21 thoroughbred training yards in Newmarket, with more than 1300 racehorses, were affected, with the horses showing signs of coughing and nasal discharge during a period of nine weeks. Many of the infected horses had been vaccinated during the previous three months with a vaccine that contained representatives from both the European (A/eq/Ne...
Abd El-Rahim IH, Hussein M.This study describes an epizootic of respiratory tract disease caused by influenza virus infection in a large population of equines in Luxor and Aswan, Upper Egypt, during the winter of 2000. The epizootic started in January and the infection rate reached its peak in February before gradually decreasing until the end of April, 2000. Horses, donkeys and mules of all ages and both sexes were affected. Free movement of the infected equines and direct contact between the animals at markets facilitated the rapid spread of the disease. The cause of the epizootic was established by use of serological...
Edlund Toulemonde C, Daly J, Sindle T, Guigal PM, Audonnet JC, Minke JM.Fifteen influenza-naive Welsh mountain ponies were randomly assigned to three groups of five. A single dose of a recombinant ALVAC vaccine was administered intramuscularly to five of the ponies, two doses, administered five weeks apart, were administered to five, and the other five served as unvaccinated, challenge controls. Two weeks after the completion of the vaccination programme, the ponies were all challenged by exposure to an aerosol of influenza virus A/eq/Newmarket/5/03. Their clinical signs were scored daily for 14 days according to a standardised scoring protocol, and nasal swabs we...
Borchers K, Daly J, Stiens G, Kreling K, Kreling I, Ludwig H.Reported here are the results of antigenic and genetic characterisation of equine influenza strains causing local outbreaks reported to the Equine Diagnostic Centre in Berlin, Germany. In 2000, equine influenza virus was detected in a nasal swab from a non-vaccinated horse using a rapid diagnostic kit, but was not successfully isolated. Partial direct sequencing of the haemagglutinin (HA1) gene, indicated that the virus was a European lineage H3N8 subtype strain representative of strains isolated in several European countries during 2000. In 2002, two equine influenza viruses were isolated fro...
Crouch CF, Daly J, Hannant D, Wilkins J, Francis MJ.Protective responses generated by vaccination with an immuno-stimulating complex (ISCOM)-based vaccine for equine influenza (EQUIP F), containing a new 'American lineage' H3N8 virus, were studied. Seven ponies in the vaccine group received two intramuscular injections of EQUIP F given 6 weeks apart. Aerosol challenge with an A/eq/Newmarket/1/93 reference strain 4 weeks after booster vaccination resulted in clinical signs of infection and viral shedding in 7 influenza-naive control animals whereas the vaccinated ponies were significantly protected from both clinical signs and virus excretion. I...
Daly JM, Yates PJ, Newton JR, Park A, Henley W, Wood JL, Davis-Poynter N, Mumford JA.Two lineages of antigenically distinct equine influenza A H3N8 subtype viruses, American and European, co-circulate. Experiments were conducted in ponies to investigate the protection induced by vaccines containing virus from one lineage against challenge infection with homologous or heterologous virus. Regression analysis showed that vaccinated ponies with average pre-challenge single radial haemolysis (SRH) antibody levels (i.e. 45-190mm2) had a higher probability of becoming infected if they were vaccinated with virus heterologous to the challenge strain than if they were vaccinated with ho...
Daly JM, Newton JR, Mumford JA.Influenza A viruses of the H3N8 subtype are a major cause of respiratory disease in horses. Subclinical infection with virus shedding can occur in vaccinated horses, particularly where there is a mismatch between the vaccine strains and the virus strains circulating in the field. Such infections contribute to the spread of the disease. Rapid diagnostic techniques are available for detection of virus antigen and can be used as an aid in control programmes. Improvements have been made to methods of standardising inactivated virus vaccines, and a direct relationship between vaccine potency measur...
Balasuriya UB.Equine influenza (EI) is a highly contagious disease of horses caused by the equine influenza virus (EIV) H3N8 subtype. EI is the most important respiratory virus infection of horses and can disrupt major equestrian events and cause significant economic losses to the equine industry worldwide. Influenza H3N8 virus spreads rapidly in susceptible horses and can result in very high morbidity within 24-48 h after exposure to the virus. Therefore, rapid and accurate diagnosis of EI is critical for implementation of prevention and control measures to avoid the spread of EIV and to reduce the economi...
Burashev Y, Strochkov V, Sultankulova K, Orynbayev M, Sansyzbay A, Sandybayev N, Nurabayev S, Savitskaya I, Rock DL, Tulman ER.Here, we report the complete genome sequencing of strains A/equine/Kostanay/9/2012(H3N8) and A/equine/LKZ/9/2012(H3N8) of the equine influenza virus belonging to Florida sublineage, clade 2. The strains were isolated in 2012 in the northern and southern regions of Kazakhstan, respectively.
Cook RF, Sinclair R, Mumford JA.An antigen capture indirect enzyme linked immunosorbent assay (ELISA) was developed to detect influenza nucleoprotein antigen in nasal secretions from horses infected with A/equine/H3N8 viruses. Results from this assay were compared with conventional virus isolation in embryonated hens eggs.
Heldens JG, Weststrate MW, van den Hoven R.Using the area under the curve (AUC) concept as is commonly used in pharmaceutical bioequivalence studies, the bioequivalence of three equine influenza vaccines was demonstrated. A retrospective analysis was performed using this technique on data generated in three trials in which each of the three vaccines had been used. In total, data from 63 pony and horse foals were used. The AUC of the single radial hemolysis (SRH) titres against Influenza A/equi-1/Prague/56 (Pr/56), A/equi-2/Newmarket-1/93, and A/equi-2/Suffolk/89 (Suf/89) were calculated for each horse. It was concluded that calculation...
Brister H, Barnum SM, Reedy S, Chambers TM, Pusterla N.We validated 2 multiplex real-time PCR (rtPCR) assays based on single nucleotide polymorphisms (SNPs) of the hemagglutinin-1 ( HA1) gene of H3N8 equine influenza A virus (EIV) to determine clade affiliation of prototype and field isolates. Initial validation of the 2 multiplex rtPCR assays (SNP1 and SNP2) was performed using nucleic acid from 14 EIV Florida sublineage clade 1 and 2 prototype strains. We included in our study previously banked EIV rtPCR-positive nasal secretions from 341 horses collected across the United States in 2012-2017 to determine their clade affiliation. All 14 EIV prot...
van Maanen C, van Essen GJ, Minke J, Daly JM, Yates PJ.An outbreak of equine influenza H3N8 in a riding school is described retrospectively with emphasis on diagnosis and putative vaccine failure. In March 1995 an outbreak of equine influenza occurred among 11 horses in a riding school, where most horses had received basic primary immunizations and several booster vaccinations against influenza. Six of the 11 diseased horses had received their last booster vaccination within 5 months of the outbreak. Nevertheless, the influenza infection spread rapidly and clinical manifestations were prominent with frequent, harsh, dry coughing often accompanied ...
Jurado-Tarifa E, Daly JM, Pérez-Écija A, Barba-Recreo M, Mendoza FJ, Al-Shuwaikh AM, García-Bocanegra I.Equine influenza is a highly contagious respiratory disease considered the most important respiratory disease in equids. Although influenza A virus (IAV) has caused outbreaks in equids worldwide, surveillance in these species in Spain has not been conducted. A cross-sectional study was carried out to determine the individual and herd prevalence of antibodies against H3N8 and H7N7 IAV in equids in Andalusia (southern Spain). Antibodies againsts IAV were measured by the single radial haemolysis assay. A spatial scan statistical analysis was carried out using a Bernoulli model. Risk factors assoc...
Na W, Lyoo KS, Yoon SW, Yeom M, Kang B, Moon H, Kim HK, Jeong DG, Kim JK, Song D.Equine influenza virus (EIV) causes a highly contagious disease in horses and other equids. Recently, we isolated an H3N8 EIV (A/equine/Kyonggi/SA1/2011) from a domestic horse in South Korea that exhibited symptoms of respiratory disease, and found that the EIV strain contained a naturally mutated NS gene segment encoding a truncated NS1 protein. In order to determine whether there was an association between the NS gene truncation and viral virulence, a reverse genetics system was applied to generate various NS gene recombinant viruses using the backbone of the H1N1 A/Puerto Rico/8/1934 (PR/8)...
Nishiura H, Satou K.An outbreak of equine influenza (H3N8) occurred among fully vaccinated racehorses in Japan from August to September, 2007. To assess the potential effectiveness of public health interventions other than vaccination (i.e. movement restriction, isolation and quarantine), which started immediately on the date of detection of the first febrile case, a simple epidemiological model was developed and applied to the observed data. The epidemic curves in five racehorse facilities revealed consistent temporal patterns: (i) a sharp increase in symptom onset of cases during the first 3 days, which is thou...
Hemida MG, Perera RAPM, Chu DKW, Alnaeem AA, Peiris M.Equine influenza virus (EIV) is one of the main causes of viral respiratory affections in horses. Little is known about the prevalence of EIV in Saudi Arabia especially the H3N8 serotype. Objective: To assess prevalence of equine influenza in horse populations in Eastern and Central Saudi Arabia. Methods: Cross-sectional study. Methods: We collected 145 sera, 323 nasal and 323 rectal swabs from horses from six major cities in Eastern and Central regions. None of the horses were vaccinated against EIV. Sera were tested in ELISA assays for influenza A type-specific antibodies and by haemagglutin...
Gahan J, Garvey M, Asmah Abd Samad R, Cullinane A.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 ...
Gahan J, Garvey M, Gildea S, Gür E, Kagankaya A, Cullinane A.In 2013, there was an outbreak of acute respiratory disease in racehorses in Turkey. The clinical signs were consistent with equine influenza (EI). The aim was to confirm the cause of the outbreak and characterise the causal virus. 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 cha...
Yamanaka T, Bannai H, Nemoto M, Tsujimura K, Kondo T, Muranaka M, Hobo S, Minamijima YH, Yamada M, Matsumura T.Equine influenza A virus (EIV) of the H3N8 subtype is an important pathogen causing acute respiratory disease in horses. Peramivir is a selective inhibitor of the influenza virus neuraminidase (NA). The characteristics of peramivir are not only its capacity for parenteral administration, but also its strong affinity for NA and slow off-rate from the NA-peramivir complex, suggesting that it could lead to a prolonged inhibitory effect and thus allow a lower dosing frequency. The aims of this study were to evaluate the inhibitory efficacy of peramivir against the NA activities of EIV in vitro and...
Murakami Y, Nerome K, Yoshioka Y, Mizuno S, Oya A.Growth characteristics of a wide range of influenza A viruses from different mammals and bird species were examined in an established line of canine kidney (MDCK) cells at an ordinary (37 degrees C) and a high temperature (42 degrees C). Although all viruses employed in the present study possessed a capability of replicating at 37 degrees C, virus growth at 42 degrees C showed considerable variation and reflected differences in the natural hosts of the isolates. All reference strains and isolates from bird species grew well in the MDCK cells maintained at 42 degrees C, but human viruses did no...
Oxburgh L, Hagström A.In this paper we describe the development of a nested RT-PCR assay for the rapid diagnosis and characterisation of influenza virus directly from clinical specimens. Viral RNA is extracted from nasal swabs by the guanidine thiocyanate extraction method, and subsequently reverse transcribed. The complementary DNA is then used as template in a nested PCR reaction. Primers designed for use in this assay are specific for three templates; (1) the nucleoprotein (NP) gene, (2) the haemagglutinin gene of the H7N7 equine influenza virus (A1), and (3) the haemagglutinin gene of the H3N8 equine influenza ...
Lee J, Park JH, Min JY.The non-structural protein of influenza A virus (NS1A protein) is a multifunctional protein that antagonizes host antiviral responses and contributes to efficient viral replication during infection. However, most of its functions have been elucidated by generating recombinant viruses expressing mutated NS1 proteins that do not exist in nature. Recently, the novel H3N8 A/Equine/Kyonggi/SA1/2011 (KG11) influenza virus was isolated in Korea from horses showing respiratory disease symptoms. KG11 virus contains a naturally truncated NS gene segment with the truncation in the NS1A coding region, res...
Lee K, Pusterla N, Barnum SM, Lee DH, Martínez-López B.Equine influenza virus (EIV) is a major infectious pathogen causing significant respiratory signs in equids worldwide. Voluntary surveillances in the United States recently reported EIV detection in horses with respiratory signs even with adequate vaccine protocols and biosecurity programs and posed a concern about suboptimal effectiveness of EIV vaccine in the United States. This study aims to determine the genetic characteristics of 58 field EIV H3N8 strains in the United States from 2012 to 2017 using the phylogenetic analysis based on the haemagglutinin (HA) gene. Amino acid substitution a...
Hannant D, Mumford JA.Cytotoxic cell precursors and/or cytotoxic memory cells were demonstrated in the peripheral blood of ponies after aerosol infection with influenza A/equine/Newmarket/79 (H3N8). In order to reveal their cytotoxic potential, peripheral blood mononuclear cells required a secondary antigenic stimulation. In vitro induced cytotoxic cells showed activity against influenza infected target cells in a 3-4 h 51Cr-release assay. The reactivity of cytotoxic cells was markedly influenced by the conditions of the secondary induction culture. If high concentrations of exogenous crude equine IL-2 were used, v...
BMC research notesSeptember 24, 2015
Volume 8 471 doi: 10.1186/s13104-015-1441-0
Boukharta M, Azlmat S, Elharrak M, Ennaji MM.Three equine influenza viruses, A/equine/Nador/1/1997(H3N8), A/equine/Essaouira/2/2004(H3N8), and A/equine/Essaouira/3/2004(H3N8), were isolated from different Equidae during local respiratory disease outbreaks in Morocco in 1997 and 2004. Their non-structural (NS) genes were amplified and sequenced. Results: The results show high homology of NS nucleotide sequences of A/equine/Nador/1/1997 with European strains (i.e., A/equine/newmarket/2/93 and A/equine/Grobois/1/1998) and clustered into the European lineage. However, NS gene of A/equine/Essaouira/2/2004(H3N8) and A/equine/Essaouira/3/2004(H...
Kwasnik M, Gora IM, Rola J, Zmudzinski JF, Rozek W.The phylogenetic analysis of influenza virus is based mainly on the variable hemagglutinin or neuraminidase genes. However, some discrete evolutionary trends might be revealed when more conservative genes are considered. We compared all available in GenBank database full length NS sequences of equine influenza virus including Polish isolates. Four nucleotides at positions A202, A237, T672 and A714 and three amino acids at positions H59, K71 and S216 which are also present in A/eq/Pulawy/2006 and A/eq/Pulawy/2008 may be discriminating for the Florida sublineage. Threonine at position 83 seems t...
Pavulraj S, Bergmann T, Trombetta CM, Marchi S, Montomoli E, Alami SSE, Ragni-Alunni R, Osterrieder N, Azab W.Equine influenza (EI) is a highly contagious acute respiratory disease of equines that is caused mainly by the H3N8 subtype of influenza A virus. Vaccinating horses against EI is the most effective strategy to prevent the infection. The current study aimed to compare the kinetics of EI-specific humoral- and cell-mediated immunity (CMI) in horses receiving either identical or mixed vaccinations. Two groups of horses were previously (six months prior) vaccinated with either Calvenza 03 EIV EHV (G1) or Fluvac Innovator (G2) vaccine. Subsequently, both groups received a booster single dose of Calv...
Virmani N, Bera BC, Shanumugasundaram K, Singh BK, Gulati BR, Singh RK, Vaid RK.India faced an epizootic of equine influenza in 2008-2009. The isolated viruses were typed as H3N8 and grouped with the clade 2 viruses of Florida sublineage on the basis of haemagglutinin (HA) gene sequence analysis. This report describes the genetic analysis and selection pressure of matrix (M) and non-structural 1 (NS1) genes of the Indian isolates. All isolates shared 98.41% and 99.54% homology with other clade 2 viruses of Asian origin for M1 and M2 amino acid (aa) sequences, respectively. There were 3 and 4 unique aa residue changes respectively in M1 and M2 proteins in all Asian isolate...
Chambers TM, Reedy SE.Serologic tests for equine influenza virus (EIV) antibodies are used for many purposes, including retrospective diagnosis, subtyping of virus isolates, antigenic comparison of different virus strains, and measurement of immune responses to EIV vaccines. The hemagglutination-inhibition (HI), single radial hemolysis (SRH), and serum micro-neutralization tests are the most widely used for these purposes and are described here. The presence of inhibitors of hemagglutination in equine serum complicates interpretation of HI assay results, and there are alternative protocols (receptor-destroying enzy...
Yamanaka T, Bannai H, Nemoto M, Tsujimura K, Kondo T, Matsumura T.In 2010, the World Organisation for Animal Health recommended the inclusion of a Florida sublineage clade2 strain of equine influenza virus (H3N8), which is represented by A/equine/Richmond/1/07 (Richmond07), in equine influenza vaccines. Here, we evaluate the antigenic differences between Japanese vaccine strains and Richmond07 by performing hemagglutination inhibition (HI) assays. Ferret antiserum raised to A/equine/La Plata/93 (La Plata93), which is a Japanese vaccine strain, reacted with Richmond07 at a similar titer to La Plata93. Moreover, two hundred racehorses exhibited similar geometr...
Ji Y, Guo W, Zhao L, Li H, Lu G, Wang Z, Wang G, Liu C, Xiang W.An antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) was developed for the detection of the equine influenza virus (EIV), employing monoclonal and polyclonal antibodies against the A/equine/Xingjiang/2007 (H3N8) nucleoprotein (NP). Immunoglobulin G antibodies were purified and used as capture or detector antibodies. The specificity of the optimized AC-ELISA was evaluated using EIV, equine herpesvirus 1 (EHV-1), equine herpesvirus 4 (EHV-4), equine arteritis virus (EAV) and Japanese encephalitis virus (JEV), resulting in only EIV specimens yielding a strong signal. A minimal concentr...
Müller I, Pinto E, Santibáñez MC, Celedón MO, Valenzuela PD.The equine influenza virus is the causal agent of influenza in horses. In July 2006, horses from various regions of Chile presented fever, serious nasal discharge, dry cough, anorexia and depression. Here we describe the isolation and characterization of the virus responsible for this outbreak. The virus was identified as equine influenza virus H3N8, since haemagglutination was inhibited by an anti-A/equi/1/H3N8 serum, but not by an anti-A/equi/1/H7N7 serum. The isolate was named A/equi/2/Lonquén/06 (H3N8). In addition, we describe the isolation and sequencing of the haemagglutinin, neuramini...
Watson J, Halpin K, Selleck P, Axell A, Bruce K, Hansson E, Hammond J, Daniels P, Jeggo M.Before 2007, equine influenza had never been diagnosed in Australia. On 22 August 2007, infection was confirmed in horses at Eastern Creek Animal Quarantine Station near Sydney. The virus subsequently isolated (A/equine/Sydney/2888-8/2007) was confirmed by sequence analysis of the haemagglutinin (HA) gene as an H3 virus of the variant American Florida lineage that is now referred to as Clade 1. The HA sequence of the virus was identical to that of a virus isolated from a contemporaneous outbreak in Japan and showed high homology to viruses circulating in North America.
Berg M, Desselberger U, Abusugra IA, Klingeborn B, Linné T.Comparative analysis by RNA oligonucleotide fingerprints of total genomic RNA as well as the individual RNA segments of equine 2 influenza A virus strains from 1963, 1968, 1979, 1984, 1987 and 1988 revealed genetic diversity. Strains from the epizootic outbreak during 1978-1979 showed minor differences among their genomes. The Swedish isolates from 1979 up to 1988 showed increasing genomic heterogeneity indicating genetic drift.
Yamanaka T, Nemoto M, Bannai H, Tsujimura K, Kondo T, Matsumura T, Gildea S, Cullinane A.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. Objective: 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 ...
Ibañez LI, Caldevilla CA, Paredes Rojas Y, Mattion N.H3N8 influenza virus strains have been associated with infectious disease in equine populations throughout the world. Although current vaccines for equine influenza stimulate a protective humoral immune response against the surface glycoproteins, disease in vaccinated horses has been frequently reported, probably due to poor induction of cross-reactive antibodies against non-matching strains. This work describes the performance of a recombinant protein vaccine expressed in prokaryotic cells (ΔHAp) and of a genetic vaccine (ΔHAe), both based on the conserved stem region of influenza hemagglut...
