PATHOGENICITY OF 3 AVIAN INFLUENZA-VIRUSES FOR LEGHORN HENS OF DIFFERENT AGES

Pronounced host effects on clinical responses to influenza virus infec tion were not observed in any of seven trials in which young (26-43 we eks) and old (65-94 weeks) leghorn hens were inoculated with low patho genic subtype H5N2, H4N8, or H3N2 virus. In two of seven trials, where hens were infected with H4N8 or H3N2 virus, morbidity rates were slig htly higher for old hens than for young hens. These observations indic ate that host age effects on the severity of uncomplicated influenza v irus infections are likely to be minimal in sexually mature chickens.