Abstract
A total of 40 viral isolates were recovered from the oral cavity in 28.4% of 141 clinically healthy horses of 5 groups. By the cross serum neutralization test, they were divided into 3 serotypes which were closely related with equine rhinovirus types 2 and 3, and strain 4442 of acid-stable equine picornavirus, respectively. Equine rhinovirus type 2 was recovered from rather young horses, and strain 4442 from both young and aged ones. Only one isolate which was identical with equine rhinovirus type 3 was isolated from a weanling. A follow-up study on virus isolation and serum neutralizing antibody detection indicated that virus titers ranging from 100.75 to 102.75 TCID50/0.1ml were detectable from the saliva of horses showing little changes in serum neutralizing antibody titer. Therefore, it is probable that equine picornavirus may normally inhabit in the oral cavity and the infection of the virus may be widespread among horses free from any clinical disease.
