Failure to establish chronic infection of the reproductive tract of the male horse with a South African asinine strain of equine arteritis virus (EAV).

Eight sexually mature horse stallions were inoculated intranasally with a South African asinine strain of EAV, a strain that was isolated from the semen of a donkey carrier. All horses developed fever, with maximum rectal temperatures of 38.9-39.9 degrees C recorded 3-6 d post challenge. Six horses showed very mild clinical signs of equine viral arteritis and two were asymptomatic. The virus was recovered from the nasopharynxes of six horses 2-7 d after inoculation, and from buffy-coat samples of all horses, 2-11 d after inoculation. Seroconversion to EAV was detected on days 8 and 10 and peak serum-virus-neutralizing antibody titres ranging from log10 1.2-1.8, on days 14-20 after challenge. The titres varied from log10 0.9-1.2 after about 10 weeks, when the experiment was terminated. In three stallions euthanased on days 5, 7 and 9 after challenge, virus was detected inconsistently in different parts of the reproductive tract and urine. No virus was isolated from the tissues of the reproductive tract collected from stallions on days 16, 23 and 68 after challenge. Five stallions were bred to six seronegative mares between 13 and 34 d post challenge. No clinical signs of EAV were observed, and neither was seroconversion detected in any of the mares after mating. No virus was recovered from semen samples collected at the time of breeding. The results of this study demonstrated that the tissues of the reproductive tracts of the stallions did not become persistently infected with a South African asinine strain of EAV.