APPLICATION OF BIOLOGICAL AND MOLECULAR TECHNIQUES TO THE DIAGNOSIS AND CONTROL OF AVIAN INFLUENZA AND OTHER EMERGING POULTRY PATHOGENS
Location: Exotic and Emerging Avian Viral Diseases Research Unit
Title: Novel routes of transmission of influenza viruses in poultry species
Submitted to: Options for the Control of Influenza Conference
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 2010
Publication Date: September 3, 2010
Citation: Pantin Jackwood, M.J., Swayne, D.E., Spackman, E., Suarez, D.L., Wasilenko, J.L., Kapczynski, D.R., Cagle, C.A. 2010. Novel routes of transmission of influenza viruses in poultry [abstract]. Options for the Control of Influenza Conference, September 2-7, 1010, Hong Kong, SAR, China. p. 111.
In order to develop better control measures against influenza it’s necessary to understand how the virus transmits in different species. The presence of avian and swine influenza virus genes in the 2009 novel H1N1 pandemic virus (pH1N1) raises the potential for infection in poultry following exposure to infected humans or swine. This is especially true for turkeys because of their known susceptibility to type A influenza viruses and the history of infection with triple reassortant viruses. To study infectivity and transmissibility of the pH1N1 virus in poultry, turkeys, chickens, domestic ducks, and Japanese quail were intranasally challenged with a pH1N1 virus. No clinical disease was produced, detection of virus replication was infrequent and only in the oropharyngeal swabs of intranasally inoculated Japanese quail. There was no contact transmission of the viruses for any of the species. This first study suggested turkeys, chickens, and domestic ducks have low risk for field infection, but Japanese quail might become infected. As in this study, several others showed that turkeys were not easy to infect when the virus was given through the intranasal route, which is considered the natural route of infection. However, outbreaks of pH1N1 have been reported in turkey breeder farms in several countries all presenting drops in egg production. In our second study, laying turkey hens were inoculated by the intranasal, intracloacal, and intrauterine route with a pH1N1 virus and it was demonstrated that the virus can infect turkeys by the intracloacal and intrauterine route, but not the intranasal route. Replication of the virus in the reproductive tract of turkey hens after intrauterine inoculation caused decreased egg production but no clinical signs. Such a route of exposure is realistic in modern turkey production when turkey hens are handled for intrauterine insemination in order to produce fertile eggs and could explain the introduction of the virus into turkey flocks. Outbreaks of low pathogenicity avian influenza (LPAI) causing drops in egg production have also been reported in chicken layers; however alternate routes of transmission of the virus have not been examined. In our third study, chicken layers were infected by the intranasal, intracloacal, or intrauterine route, with one of two LPAI viruses: a chicken adapted virus (A/Ck/CA/1255/02 H6N2) and a live bird market isolate (A/Ck/NJ/1220/97 H9N2). All chickens became infected with the H6N2 virus when exposed by any of the three routes and transient drops in egg production were observed. On the other hand, only 1 or 2 hens from each of the groups inoculated with the H9N2 virus presented evidence of infection. This indicates that LPAI viruses can also transmit in chickens through other routes besides the intranasal route. In conclusion, influenza viruses can transmit to poultry by different routes of exposure; however this transmission is host and virus dependent.