Isolation from turkey breeder hens of a reassortant H1N2 influenza virus with swine, human, and avian lineage genes

Type A influenza viruses can infect a wide range of birds and mammals, but influenza in a particular species is usually considered to be species specific. However, infection of turkeys with swine H1N1 viruses has been documented on several occasions. This report documents the isolation of an H1N2 influenza virus from a turkey breeder flock with a sudden drop in egg production. Sequence analysis of the virus showed that it was a complex reassortant virus with a mix of swine-, human-, and avian-origin influenza genes. A swine influenza virus with a similar gene complement was recently reported from pigs in Indiana. Isolation and identification of the virus required the use of nonconventional diagnostic procedures. The virus was isolated in embryonated chicken eggs by the yolk sac route of inoculation rather than by the typical chorioallantoic sac route. Interpretation of hemagglutination-inhibition test results required the use of turkey rather than chicken red blood cells, and identification of the neuraminidase subtype required the use of alternative reference sera in the neuraminidase-inhibition test. This report provides additional evidence that influenza viruses can cross species and cause a disease outbreak, and diagnosticians must be aware that the variability of influenza viruses can complicate the isolation and characterization of new isolates.