Evidence of prior infection with influenza A/Texas/77 (H3N2( virus in dogs with clinical parainfluenza.

Eighty dogs exhibiting clinical signs of respiratory disease were sampled for influenza virus isolation and serologically tested for hemagglutination inhibiting antibody to influenza A/Hong Kong/68, A/Victoria/75, A/Texas/77 and A/USSR/77. Forty-one animals without clinical signs of respiratory disease were also examined serologically. Hemagglutinating agents were isolated from nasal and/or pharyngeal swabs taken from 21 of the 80 dogs with clinical respiratory disease. Twenty of these 21 isolates were canine parainfluenza virus. Twenty-one of 80 clinically ill animals (26.3%) and eight of 41 normal animals (19.5%) had low level hemagglutination inhibiting antibody to influenza A/Texas/77. There was no evidence that human influenza caused the respiratory disease in the dogs included in this study, since none had an increase in hemagglutination inhibiting antibody to influenza in convalescent sera. The presence of antibody to A/Texas/77, however, does suggest the possibility that these dogs had at some time been infected with this virus, and that dogs could play a role in the epidemiology of influenza in man.