Experimental exposure of pregnant mares to the asinine-94 strain of equine arteritis virus.

The research is about the study of impacts when pregnant mares are exposed to equine arteritis virus (EAV) – asinine-94 strain. Clinical observations, virological testing and serological responses are explored for the mother mares and their offspring post exposure.

Study Methods and Initial Results

• Using the asinine-94 strain of equine arteritis virus (EAV), 10 pregnant mares were purposefully exposed through different methods: intranasal, intramuscular, intravenous and contact exposure.
• All the mares that were inoculated showed signs of pyrexia (fever), and five also demonstrated mild symptoms related to EAV infection while two showed no symptoms.
• Viraemia (the presence of the virus in the bloodstream) was found in all the inoculated mares. Six mares proved to be shedding the virus from their respiratory tract.

Re-challenge and Testing Results

• Five of the mares were re-challenged with the EAV virus via the intranasal method at 7 weeks and 15 weeks after the initial inoculation. Mild conjunctivitis was the only observed clinical sign after re-inoculation.
• Two of the re-inoculated mares displayed EAV in their blood a few days post-re-challenge, as per buffy coat cultures.
• The virus wasn’t detected in colostrum and milk samples taken postpartum during the first week. And, all inoculated mares converted to the presence of EAV antibodies 8-12 days after exposure and also post-re-exposure.
• Some of the mares that were kept in close contact during post-inoculation and re-challenge phase showed no clinical signs of EAV. Interestingly, serum neutralising antibodies were found in one such mare, while EAV-specific IgG was detected in another mare’s colostrum.

The Effect on Offspring

• Eight out of the ten exposed mares gave birth to healthy foals, except one who was born prematurely.
• However, seven foals developed fever along with variable clinical symptoms shortly after birth. These lead to severe conditions, with three dying in less than a week and two being euthanized due to septicemia (blood poisoning) at one month of age.
• Despite these outcomes, no EAV was recovered from the placenta, from neonate’s blood samples, or from tissues of the deceased and euthanized foals.
• Also, no EAV was isolated from one mare and her fetus three weeks after the mare was re-challenged.