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Equine viral arteritis
New Information about
From The Horse Report Jan. 1999
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ine viral arteritis
Equine arteritis virus (EAV) is distributed throughout the world and causes periodic outbreaks of equine viral arteritis (EVA) in horses. Since the mid-1980s, the incidence of EVA has increased and has become a significant concern to the equine industry. EAV infection can cause pneumonia in very young foals, influenza-like illness in adult horses, abortion in pregnant mares and persistent infection of stallions. Persistently infected stallions act as a natural reservoir and shed the virus in their semen. During natural or artificial breeding, the virus is transmitted to susceptible mares precipitating new outbreaks of EVA, spreading the virus to other susceptible horses. Export/import restrictions on horses, particularly stallions and/or their semen, have a major economic impact on the equine industry. Recently, the number of EAV-carrier stallions and infected semen imported into the United States, particularly from Europe, has increased. Some of these stallions and semen have been responsible for causing economically damaging outbreaks of EVA, including abortions, in the United States. The situation is exacerbated by the current lack of adequate control measures for EVA, thus, the United States has become a virtual "dumping ground" for EAV shedding stallions and infected semen. In response to these recent outbreaks of EVA, the American Horse Industry Council has appointed a working group to develop a breeding code to identify carrier stallions who shed the virus in their semen. Critical to the success of this program is the development of a very specific, highly sensitive, rapid and more accessible test to detect EAV in semen as well as in other clinical specimens. The current test for the detection of EAV in stallion semen is time consuming, expensive and cumbersome. Information from this study will be used to develop a more reliable and less expensive test for the detection of this virus. The development of a more accurate and more easily run test will not only facilitate the rapid detection of carrier stallions, but will also allow for easier identification of the virus in other clinical Samples such as blood, tissue from aborted fetuses, and nasal swabs. Therefore, a new and improved diagnostic assay is under development at The University of California, Davis, by amplifying a highly conserved region of the EAV genome by RT-PCR. Sensitive reverse transcription and polymerase chain reaction (RT-PCR) based methods for detection of EAV in equine semen recently have been developed, although they are not yet widely available. In this study, the researchers propose to further improve this RT-PCR based assay by 1) eliminating several sample manipulation steps using an improved enzyme, 2) reducing false positive results by eliminating sample carryover, and 3) using a colorimetric substrate detection system to measure the absorbence in microwell plates. The test will be validated using semen from EAV carrier stallions and clinical specimens. The research team is headed by N. James MacLachlan, and includes Udeni B. R. Balasuriya, Jodi F. Hedges, Peter J. Timoney, William H. McCollum, W. David Wilson, and Irwin K. M. Liu.
176
JOURNAL OF EQUINE VETERINARY SCIENCE
From The Horse Report Jan. 1999
~
ine viral arteritis
Equine arteritis virus (EAV) is distributed throughout the world and causes periodic outbreaks of equine viral arteritis (EVA) in horses. Since the mid-1980s, the incidence of EVA has increased and has become a significant concern to the equine industry. EAV infection can cause pneumonia in very young foals, influenza-like illness in adult horses, abortion in pregnant mares and persistent infection of stallions. Persistently infected stallions act as a natural reservoir and shed the virus in their semen. During natural or artificial breeding, the virus is transmitted to susceptible mares precipitating new outbreaks of EVA, spreading the virus to other susceptible horses. Export/import restrictions on horses, particularly stallions and/or their semen, have a major economic impact on the equine industry. Recently, the number of EAV-carrier stallions and infected semen imported into the United States, particularly from Europe, has increased. Some of these stallions and semen have been responsible for causing economically damaging outbreaks of EVA, including abortions, in the United States. The situation is exacerbated by the current lack of adequate control measures for EVA, thus, the United States has become a virtual "dumping ground" for EAV shedding stallions and infected semen. In response to these recent outbreaks of EVA, the American Horse Industry Council has appointed a working group to develop a breeding code to identify carrier stallions who shed the virus in their semen. Critical to the success of this program is the development of a very specific, highly sensitive, rapid and more accessible test to detect EAV in semen as well as in other clinical specimens. The current test for the detection of EAV in stallion semen is time consuming, expensive and cumbersome. Information from this study will be used to develop a more reliable and less expensive test for the detection of this virus. The development of a more accurate and more easily run test will not only facilitate the rapid detection of carrier stallions, but will also allow for easier identification of the virus in other clinical Samples such as blood, tissue from aborted fetuses, and nasal swabs. Therefore, a new and improved diagnostic assay is under development at The University of California, Davis, by amplifying a highly conserved region of the EAV genome by RT-PCR. Sensitive reverse transcription and polymerase chain reaction (RT-PCR) based methods for detection of EAV in equine semen recently have been developed, although they are not yet widely available. In this study, the researchers propose to further improve this RT-PCR based assay by 1) eliminating several sample manipulation steps using an improved enzyme, 2) reducing false positive results by eliminating sample carryover, and 3) using a colorimetric substrate detection system to measure the absorbence in microwell plates. The test will be validated using semen from EAV carrier stallions and clinical specimens. The research team is headed by N. James MacLachlan, and includes Udeni B. R. Balasuriya, Jodi F. Hedges, Peter J. Timoney, William H. McCollum, W. David Wilson, and Irwin K. M. Liu.
176
JOURNAL OF EQUINE VETERINARY SCIENCE