Effect of the South African asinine-94 strain of equine arteritis virus (EAV) in pregnant donkey mares and duration of maternal immunity in foals.

This research examines the effects of the South African asinine-94 strain of equine arteritis virus on pregnant donkeys and the subsequent maternal immunity in their offspring. The results suggest that the virus doesn’t provoke abortions in pregnant donkeys, and that the babies do not demonstrate carrier status despite maternal infection during pregnancy.

Research Methodology and Results

• The research studied the clinical, virological, and serological responses in five pregnant donkey mares after deliberately exposing them to the South African asinine-94 strain of equine arteritis virus (EAV). This is a viral infection known for causing respiratory disease and occasional abortions in equine species.
• All of the exposed mares endured fever ranging from 39.1 to 40.7 degrees Celsius, mild depression, and a serous ocular and nasal discharge. Also, mild conjunctivitis was found in three mares. The virus was detectable from nasopharynx and blood samples.
• Despite these symptoms, none of the mares aborted. This indicates that the asinine-94 strain of EAV does not trigger abortion in pregnant donkeys, contrary to its effects in other equines.
• The concentration of EAV-neutralizing antibody in donkey’s first milk post-delivery was two to eight times higher than in blood samples collected at the time of childbirth, indicating a transfer of immunity from the mother to the baby.

Maternal Immunity in Foals

• After giving birth, no virus could be isolated from the donkey’s placenta. The offspring born to infected mares were clinically normal at birth and during the subsequent observation period of 1-2 months. This hints at no viral transmission happening during birth.
• No evidence of EAV was found in the newborn’s blood samples at birth or thereafter (days 1, 2 and 7). Neither was there any EAV-specific serum-neutralizing or IgG ELISA antibody detected in sera collected immediately after birth before the newborns started nursing.
• However, the maternally obtained immunity against EAV from colostrum — the donkey’s first milk — gradually declined and was undetectable by either the VN test or ELISA within 2-3 months after birth. This suggests that the immunity provided to the offspring by the infected mothers is only temporary and may leave them susceptible to the virus later-in-life.

In conclusion, the asinine-94 strain of EAV does not cause abortion in pregnant donkeys or create a carrier state in foals born to infected mothers. The maternal antibodies transferred through the colostrum, whilst providing brief initial protection, wane within a few months.