Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2005
Publication Date: 5/5/2005
Citation: Tang, Y., Lee, C.W., Zhang, Y., Senne, D.A., Dearth, R., Byrum, B., Perez, D., Suarez, D.L., Saif, Y.M. 2005. Isolation and characterization of h3n2 influenza a virus from turkeys. Avian Diseases 49:207-213. Interpretive Summary: Influenza is a virus that can infect man and many different domestic animals. Although all these influenza viruses are genetically similar to one another, typically influenza viruses from one species does not infect another species. However, recently an H3N2 virus was isolated from a turkey farm in Ohio. This virus caused a costly drop in egg production. Although the virus was identified as influenza using a PCR test, it was difficult to grow the virus in the laboratory using the normal techniques. The virus, when sequenced, was shown to be not an avian influenza virus, but a swine influenza virus. This is one of the first reports of a swine H3N2 virus infecting turkeys. If these infections become more common, then farmers will need to start vaccinating turkeys for this type of avian influenza also.
Technical Abstract: Five 34-wk-old turkey breeder layer flocks of 2550 birds each in a single premise in Ohio experienced a drop in egg production from late January to early February, 2004. Tracheal swabs (n = 60), cloacal swabs (n = 50), and convalescent sera (n = 110) from the flocks were submitted to the laboratory for diagnostics. Virus isolation was attempted using SPF embryonating chicken eggs, Vero and MDCK cells. Virus characterization was performed using agar gel immunodiffusion (AGID), hemagglutination (HA) test, hemagglutination inhibition (HI) test, virus neutralization (VN) test, RT-PCR, sequencing, and phylogenetic analysis. A presumptive influenza virus was successfully propagated and isolated on the first passage in MDCK cells, but not in Vero cells or SPF chicken embryos initially. After 6 passages in MDCK cells, it was possible to propagate the isolate in SPF chicken embryos. Preliminary sequence analysis of the isolated virus confirmed that it was influenza A virus with 99% (235/236) identity with the matrix gene of a swine influenza A virus, A/Swine/Illinois/100084/01 (H1N2). However, it was not possible to subtype the virus using conventional serotyping methods. The results of genetic characterization of the isolated virus showed that it was H3N2 subtype, and was designated as A/Turkey/OH/313053/04 (H3N2). Phylogenetic analysis of the 8 gene segments of the virus indicated that A/Turkey/OH/313053/04 (H3N2) isolate was most closely related to the triple-reassortant H3N2 swine viruses (A/Swine/WI/14094/99 (H3N2) circulating among pigs in the U.S. since 1998, which contains gene segments from avian, swine, and human viruses. The A/Turkey/OH/313053/04 (H3N2) isolated from turkeys in this study was classified as low pathogenic avian influenza A virus since it only caused primarily a drop in egg production with only minor clinical signs and no mortality.