Lateral transmission of equine arteritis virus among Lipizzaner stallions in South Africa.

The research article discusses a study conducted on a group of Lipizzaner stallions in South Africa infected with the Equine Arteritis Virus (EAV). The objective of the study was to trace the spread of the virus among the stallions, identify its origin and investigate how it was transmitted among the infected stallions.

Study Background and Objective

• The research began in 1995 when seven Lipizzaner stallions in South Africa tested positive for EAV. A stallion imported from Yugoslavia in 1981 was determined to be an EAV carrier in 1988 and despite being quarantined, the virus had managed to spread to other stallions at the Lipizzaner Centre.
• This spurred a study to trace the phylogenetic relationships between the strain of EAV shed in the semen of the original carrier stallion and other strains recovered from five other stallions. The researchers also sought to determine how the lateral transmission of EAV occurred among seven nonbreeding stallions at the Centre.

Methods and Results

• The method involved isolating EAV from the semen of the infected stallions using RK-13 cells. The viral RNA was then reverse transcribed and amplified using ORF 5-specific primers and then subjected to sequence and phylogenetic analysis.
• The results confirmed that the strains of EAV in the six infected stallions were closely related and probably originated from the same source, the stallion imported from Yugoslavia. The study also confirmed lateral transmission of the EAV among the seven nonbreeding stallions at the Centre. The researchers speculate that the stallions could have been exposed to the virus from bedding or other inanimate objects (fomites) contaminated with EAV-infected semen.

Conclusions

• The research confirmed that the lateral transmission of EAV could occur from infected stallions shedding the virus to susceptible, in-contact horses, including other stallions, which may then become persistently infected.
• The findings suggest that transmission of the virus could start with the infection of one or more stallions through exposure to contaminated bedding or other fomites. This also supports the lateral spread of a single, unique strain of EAV within a group.