Susceptibility of birds to type-B influenza virus.

Among Zoo birds and migrating wild birds examined serologically during an outbreak due to influenza B virus, 4.1% were found to have serum antibodies to the agent. Evidence of avian susceptibility to the agent was emerging from reisolations of the virus and primary and secondary HI antibody response of the birds in subsequent infection experiments performed on adult pheasants and mallards, as well as one-day-old domestic ducklings and chicks. The virus persisted in the pheasants for at least three weeks, and adult pheasants, mallards and domestic ducklings were found to transmit it by contact to part of their susceptible mates.