Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2001
Publication Date: N/A
Interpretive Summary: Influenza virus can infect many different animals including chickens, turkeys, pigs, horses and humans. The original source of influenza viruses are from wild birds, like ducks and gulls, but when influenza is passed to a new animal, the virus can make genetic changes to allow it to easily grow in the new animal. These changes make the virus unique for that new animal. For example, human influenza viruses usually only infect humans and chicken influenza viruses normally only infect chickens. However, cases of human viruses infecting pigs and chicken viruses infecting people have been described. Recently a turkey flock from Missouri was diagnosed with an unusual influenza virus. This virus had genes that came from three different sources including swine, human and bird. This was the first time that an influenza virus with this mixed background was seen in turkeys, although a similar virus had been reported in swine in 1999. The turkeys farm was located next a swine farm, and the swine farm may have been the source of infection. Farms in the area were vaccinated against this virus, and that has prevented new outbreaks of disease.
Technical Abstract: 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 have been documented on several occasions. This report documents the isolation of a 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 also recently reported from pigs in Indiana. Isolation and identification of the virus required the use of non-conventional 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 eof turkey rather than chicken RBCs and identification of the neuraminidase subtype required the use of alternative reference serums 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.