[Pathogenicity of equine influenza viruses in chickens]

In the present paper the pathogenicity of equine subtype A/equi 1 (H7N7) and A/equi 2 (H3N8) for chicks was studied. Strains previously isolated in Brazil, representatives of both subtypes, were used. Eight experiments were performed for A/equi 2, using 89 chicks (4 to 18-day old). Six hundred thirty three samples of cloacal material were collected from 01 to 15 days pos-infection (p.i.) and inoculated in 11-day old chick embryos for recuperation of virus. Twelve samples showed positive results. The recuperated viruses were identified with specific antiserum in hemagglutination inhibition test (HI). Blood samples of all chicks collected prior to infection showed no antibodies to both subtypes. Chicks inoculated with A/equi 2 virus were bled 18 to 21 days p.i. Out of 89, seventy one (79.8%) serums showed different levels of antibodies at HI tests. Seventy chicks were inoculated with A/equi 1 subtype. Five hundred forty three samples of cloacal material were harvested and inoculated in embryonated chick eggs. No recuperation of virus occurred. However, all the inoculated chickens showed seroconversion. Chicks infected with A/equi 2 may shed virus in feces. No signs of disease were noted in the inoculated chicks.