Abstract
Nine horses were inoculated intramuscularly with the modified Bucyrus strain of equine arteritis virus. Of them, eight showed body temperature elevated slightly or moderately and all experienced mild lymphopenia. No other clinical signs of disease occurred at all. Relatively low titers of both serum neutralizing and complement fixation antibodies were detected. Their highest titers did not last long. Virus recovered transiently from nasal and rectal swabs and buffy coat of 2 horses and continually from buffy coat of another 2 horses. The distribution and concentration of virus in tissues and body fluids of horses could be tested on the 5th day post inoculation (PI). No virus was detected from horses sacrificed on the 7th, 9th, 11th or 13th day PI. Virus was contained, however, in the submandibular lymph nodes, liver, and ovary of a horse sacrificed on the 34th day PI. The challenge exposure to the virulent virus was conducted in 2 horses on the 36th day PI and one in the 9th month PI. None of these horses showed any sign of arteritis. No contact infection of the modified virus was suggested in one horse which had been kept with an inoculated horse for 9 months, since the former was negative for immunological response, and then showed acute arteritis after exposure to the virulent virus.
