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Seroprevalence of Equine Rhinitis Virus in Louisiana Horses
S18
9th ICEID Abstracts / Journal of Equine Veterinary Science 32 (2012) S3-S95
Equine influenza caused by equine influenza virus (H3N8) is considered the most important respiratory disease of horses due to its rapid transmission. Inactivated vaccines are widely used for limiting the spread of disease and reducing the clinical severity in individual level. However, many outbreaks have been reported among vaccinated horses primarily because of the antigenic differences between the vaccine strains and epidemic strains. It is therefore necessary to periodically review the strain composition of vaccines. The hemagglutination inhibition (HI) test has been widely used for assessing the cross-reactive antibody responses induced by vaccines to epidemic strains. Though there is general agreement between results of HI tests and vaccine efficacies, it remains unclear whether cross-antibody titer measured by the HI test correlates with crossneutralizing reactivity. Here, we assessed the cross-reactivity of the antibodies elicited by the Japanese local vaccine strains to the current epidemic strains, by virus neutralization (VN) test. We made the horse antisera by inhalations of the Japanese vaccine strains [A/equine/La Plata/1993 (American) and A/equine/Ibaraki/1/2007 (Fc1)] [108.3 50% egg infectious dose (EID50)/horse each] to horses. Two weeks after the inhalations, each serum was taken from each horse. All the antisera were treated with trypsin-heatpotassium metaperiodate to remove non specific inhibitors before VN tests. Then the required final dilution of treated antiserum (1:8) was prepared and absorbed with packed chicken red blood cells. Two-fold serial dilutions of the antiserum were prepared and added to the equal volume of each virus (approx. 104.0 EID50/200 ml). After incubation for 60 min at 34 C, 200 ml of the mixture was injected into an embryonated hen’s egg (5 eggs per each serum dilution). After three overnights incubation at 34 C, the allantoic fluids were harvested and examined hemagglutination activities. VN titers were expressed as the log (2) of the reciprocals of the dilution of antisera which reduced infectivity to 1 EID50/200 ml. Whereas the horse antiserum raised to A/equine/Ibaraki/1/2007 (Fc1) showed significantly lower VN titer (6.2) to A/equine/Yokohama/aq13/2010 (Fc2) than that to the homologous virus (9.0), the horse antiserum raised to A/equine/La Plata/93 neutralized A/equine/Yokohama/aq13/2010 well at the similar VN titer (9.3) to the homologous VN titer (9.2). The World Organization for Animal Health (OIE) annually reports the antigenic traits of circulating viruses in the world. It is recommended that vaccines for the international market should contain both Fc1 and Fc2 viruses. Our results however showed that the inoculation of A/equine/La Plata/93, which is one of the Japanese local vaccine strains and not genetically classified into Fc2, can elicit the antibody cross-neutralizing the Fc2 viruses well in horse serum. Seroprevalence of Equine Rhinitis Virus in Louisiana Horses F.M. Andrews 1, C. Durussel 2, F. Garza, Jr. 1, P. Loftin 1, S. Zaccarato 2, M.L. Keowen 1, and R. Keene 3 1 Equine Health Studies Program, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, 2 Ecole Nationale Veterinaire De Toulouse, Toulouse, France, 3 Boehringer Ingelheim Vetmedica, Inc. St. Joseph, MO
Respiratory disease is common in race horses and infectious respiratory disease was ranked second, only to colic, among equine practitioners as the most important medical disease concern. The economic impact of viral induced infectious respiratory disease, such as Equine Influenza virus (EIV) and Equine Herpes virus (EHV), on the horse industry is substantial. However, little is known about Equine Rhinitis Virus (serotypes ERV-1 and ERV-2) in racehorses at race tracks and training facilities in Louisiana. The purpose of this study was to determine the seroprevalence of ERV in horses at a racetrack, training center, and a university farm in Southern Louisiana. Blood samples were collected from horses housed at a Louisiana racetrack (n ¼ 77), a Louisiana Thoroughbred training facility (n¼ 44) and at the Louisiana State University Equine Health Studies Program Thoroughbred and Quarter Horse research and teaching farm (n¼55). Samples were allowed to clot and centrifuged at 2000 x g for 15 minutes. Serum from each horse was harvested and placed into 2.0 ml cryogenic vials and stored at -80oC until serum titer determinations for ERV-1 and ERV-2 were made. All samples were shipped by overnight carrier for analysis. Serum neutralization (SN) titers were done using a standard cytopathologic assay performed by the federally accredited lab at the Cornell Animal Health Diagnostic Center in Ithaca, NY. Titers were reported as inverse of the ratio. Serum neutralizing antibodies to ERV-1 and ERV-2 were present in 84.1% and 94.9 %, respectively, of horses at these facilities. Mean SN titers were relatively low for ERV-2 (57.05 +/- 9.49) in horses at these facilities, while SN titers to ERV-1 were significantly higher, (p < 0.05), in horses at the racetrack (392.7 +/- 45.9) and in horse at the university farm (535.8 +/- 91.6), when compared to horses at the training center (42.6 +/- 2.3). We concluded that ERV-1 and ERV-2 SN antibodies were present in horses at a racetrack, training center, and a university farm in Louisiana. Also, SN titers to ERV-1 were higher in horses housed at the race track and university farm, compared to horses at the training facility. The difference in SN titers at these facilities was not apparent but may be due to age, as horses at the racetrack and university farm were older allowing more time for virus exposure and antibody production. ERV appears to be prevalent in horses in Louisiana and warrants further epidemiologic investigation to determine its impact on racing and training and the need for vaccine development to reduce impact. Rhodococcus equi’s Extreme Hydrogen Peroxide Resistance is Mainly Conferred by One of its Four Catalase Genes P. Bidaud 1, L. Hébert 1, C. Barbey 1, Anne-Cécile Appourchaux 1, R. Torelli 2, M. Sanguinetti 2, C. Laugier 1, and S. Petry 1 1 ANSES, Dozulé Laboratory for Equine Diseases, Unit Bacteriology and Parasitology, Goustranville, France, 2 Catholic University of Sacred Heart, Institute of Microbiology, Rome, Italy
Rhodococcus equi is the agent of rhodococcosis, one of the most important diseases in foals aged from 1 to 6 months.
9th ICEID Abstracts / Journal of Equine Veterinary Science 32 (2012) S3-S95
Equine influenza caused by equine influenza virus (H3N8) is considered the most important respiratory disease of horses due to its rapid transmission. Inactivated vaccines are widely used for limiting the spread of disease and reducing the clinical severity in individual level. However, many outbreaks have been reported among vaccinated horses primarily because of the antigenic differences between the vaccine strains and epidemic strains. It is therefore necessary to periodically review the strain composition of vaccines. The hemagglutination inhibition (HI) test has been widely used for assessing the cross-reactive antibody responses induced by vaccines to epidemic strains. Though there is general agreement between results of HI tests and vaccine efficacies, it remains unclear whether cross-antibody titer measured by the HI test correlates with crossneutralizing reactivity. Here, we assessed the cross-reactivity of the antibodies elicited by the Japanese local vaccine strains to the current epidemic strains, by virus neutralization (VN) test. We made the horse antisera by inhalations of the Japanese vaccine strains [A/equine/La Plata/1993 (American) and A/equine/Ibaraki/1/2007 (Fc1)] [108.3 50% egg infectious dose (EID50)/horse each] to horses. Two weeks after the inhalations, each serum was taken from each horse. All the antisera were treated with trypsin-heatpotassium metaperiodate to remove non specific inhibitors before VN tests. Then the required final dilution of treated antiserum (1:8) was prepared and absorbed with packed chicken red blood cells. Two-fold serial dilutions of the antiserum were prepared and added to the equal volume of each virus (approx. 104.0 EID50/200 ml). After incubation for 60 min at 34 C, 200 ml of the mixture was injected into an embryonated hen’s egg (5 eggs per each serum dilution). After three overnights incubation at 34 C, the allantoic fluids were harvested and examined hemagglutination activities. VN titers were expressed as the log (2) of the reciprocals of the dilution of antisera which reduced infectivity to 1 EID50/200 ml. Whereas the horse antiserum raised to A/equine/Ibaraki/1/2007 (Fc1) showed significantly lower VN titer (6.2) to A/equine/Yokohama/aq13/2010 (Fc2) than that to the homologous virus (9.0), the horse antiserum raised to A/equine/La Plata/93 neutralized A/equine/Yokohama/aq13/2010 well at the similar VN titer (9.3) to the homologous VN titer (9.2). The World Organization for Animal Health (OIE) annually reports the antigenic traits of circulating viruses in the world. It is recommended that vaccines for the international market should contain both Fc1 and Fc2 viruses. Our results however showed that the inoculation of A/equine/La Plata/93, which is one of the Japanese local vaccine strains and not genetically classified into Fc2, can elicit the antibody cross-neutralizing the Fc2 viruses well in horse serum. Seroprevalence of Equine Rhinitis Virus in Louisiana Horses F.M. Andrews 1, C. Durussel 2, F. Garza, Jr. 1, P. Loftin 1, S. Zaccarato 2, M.L. Keowen 1, and R. Keene 3 1 Equine Health Studies Program, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, 2 Ecole Nationale Veterinaire De Toulouse, Toulouse, France, 3 Boehringer Ingelheim Vetmedica, Inc. St. Joseph, MO
Respiratory disease is common in race horses and infectious respiratory disease was ranked second, only to colic, among equine practitioners as the most important medical disease concern. The economic impact of viral induced infectious respiratory disease, such as Equine Influenza virus (EIV) and Equine Herpes virus (EHV), on the horse industry is substantial. However, little is known about Equine Rhinitis Virus (serotypes ERV-1 and ERV-2) in racehorses at race tracks and training facilities in Louisiana. The purpose of this study was to determine the seroprevalence of ERV in horses at a racetrack, training center, and a university farm in Southern Louisiana. Blood samples were collected from horses housed at a Louisiana racetrack (n ¼ 77), a Louisiana Thoroughbred training facility (n¼ 44) and at the Louisiana State University Equine Health Studies Program Thoroughbred and Quarter Horse research and teaching farm (n¼55). Samples were allowed to clot and centrifuged at 2000 x g for 15 minutes. Serum from each horse was harvested and placed into 2.0 ml cryogenic vials and stored at -80oC until serum titer determinations for ERV-1 and ERV-2 were made. All samples were shipped by overnight carrier for analysis. Serum neutralization (SN) titers were done using a standard cytopathologic assay performed by the federally accredited lab at the Cornell Animal Health Diagnostic Center in Ithaca, NY. Titers were reported as inverse of the ratio. Serum neutralizing antibodies to ERV-1 and ERV-2 were present in 84.1% and 94.9 %, respectively, of horses at these facilities. Mean SN titers were relatively low for ERV-2 (57.05 +/- 9.49) in horses at these facilities, while SN titers to ERV-1 were significantly higher, (p < 0.05), in horses at the racetrack (392.7 +/- 45.9) and in horse at the university farm (535.8 +/- 91.6), when compared to horses at the training center (42.6 +/- 2.3). We concluded that ERV-1 and ERV-2 SN antibodies were present in horses at a racetrack, training center, and a university farm in Louisiana. Also, SN titers to ERV-1 were higher in horses housed at the race track and university farm, compared to horses at the training facility. The difference in SN titers at these facilities was not apparent but may be due to age, as horses at the racetrack and university farm were older allowing more time for virus exposure and antibody production. ERV appears to be prevalent in horses in Louisiana and warrants further epidemiologic investigation to determine its impact on racing and training and the need for vaccine development to reduce impact. Rhodococcus equi’s Extreme Hydrogen Peroxide Resistance is Mainly Conferred by One of its Four Catalase Genes P. Bidaud 1, L. Hébert 1, C. Barbey 1, Anne-Cécile Appourchaux 1, R. Torelli 2, M. Sanguinetti 2, C. Laugier 1, and S. Petry 1 1 ANSES, Dozulé Laboratory for Equine Diseases, Unit Bacteriology and Parasitology, Goustranville, France, 2 Catholic University of Sacred Heart, Institute of Microbiology, Rome, Italy
Rhodococcus equi is the agent of rhodococcosis, one of the most important diseases in foals aged from 1 to 6 months.