Passive transfer, rate of decay, and protein specificity of antibodies against equine arteritis virus in horses from a Standardbred herd with high seroprevalence.

The study investigates the decay rate of antibodies for the Equine Arterivirus in foals and its mode of transmission in a Standardbred horse farm with high infection rate. The results show that foals can be safely vaccinated after 8 months and highlights the central role of stallions in spreading the virus sexually.

Objective of the Study

• The researchers aimed to understand the decay rate of passively acquired antibodies in Standardbred foals in a farm with a high prevalence of Equine Arteritis Virus (EAV).
• They sought to ascertain whether the virus transmission on the farm was vertical (direct mother-to-foal transmission) or horizontal (from other infected horses).

Methodology

• Their investigation was a repeated-measures study on 46 Standardbred horses comprising of 15 brood mares with their foals, 5 stallions, and 11 young horses.
• They conducted serum neutralization and western immunoblot analyses on serum samples from the horses to detect EAV-specific antibodies.
• The half-life of passively acquired antibodies in the foals was determined by regression analysis.

Results

• Most of the mares (14 out of 15) werefound to be seropositive for EAV. Their foals, after being suckled by the mares, also tested positive.
• The estimated average half-life of the passively acquired antibodies in the foals’ serum samples was 32 days.
• The one foal born to a seronegative dam and all 11 young horses remained seronegative for EAV.
• At least 2 of the 5 stallions were found to be long-term carriers that were shedding the EAV virus in their semen continually.
• Among the seropositive serum samples presented for immunoblot examination, the most frequently acknowledged was the M protein of the EAV.

Conclusions

• The researchers found a basis for administering a modified-live EAV vaccine to foals after they were eight months old without risk of interference from maternal antibodies, irrespective of the serologic condition of the foal’s dam.
• The data suggests that horizontal transmission of EAV via the respiratory tract was uncommon within the farm. This implies that mares were primarily infected through sexual transmission of the virus from stallions who were carriers.