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Title: Low pathogenicity avian influenza viruses infect chicken layers by different routes of inoculation

Author
item Pantin Jackwood, Mary
item Smith, Diane
item Wasilenko, Jamie
item Spackman, Erica

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2011
Publication Date: 6/15/2012
Citation: Pantin Jackwood, M.J., Smith, D.M., Wasilenko, J.L., Spackman, E.V. 2012. Low pathogenicity avian influenza viruses infect chicken layers by different routes of inoculation. Avian Diseases. 56:276-281.

Interpretive Summary: Avian influenza (AI) continues to be a threat to commercial poultry. In order to develop better control measures against AI we need to understand how the virus transmits. In a previous study we found that no or minimal infection occurred in turkeys when given a low pathogenicity (LP) AI virus intranasally (IN). However, we showed that the virus could infect turkey hens by the intracloacal (IC) and intraoviduct (IO) routes, possibly explaining the drops of egg production observed in turkey breeder farms. In the present study, we demonstrated we could also infect chicken layers by the IC or IO routes. We used two LPAI viruses: a poultry origin virus, A/chicken/CA/1255/02 (H6N2), and a live bird market isolate, A/chicken/NJ/12220/97 (H9N2). Only hens IN inoculated with the H6N2 virus presented mild clinical signs. However a decrease in number of eggs laid was observed in all virus-inoculated groups when compared to non-infected hens. In conclusion, LPAI viruses can also infect chickens through other routes besides the intranasal route, which is considered the natural route of exposure.

Technical Abstract: In order to develop better control measures against avian influenza (AI) it’s necessary to understand how the virus transmits in poultry. In a previous study in which the infectivity and transmissibility of the pandemic H1N1influenza virus was examined in different poultry species, we found that no or minimal infection occurred in chicken and turkeys intranasally (IN) inoculated with the virus. However, we demonstrated that the virus can infect laying turkey hens by the intracloacal (IC) and intraoviduct (IO) routes possibly explaining the drops of egg production observed in turkey breeder farms. Such novel routes of exposure to the virus have not been previously examined in chickens and could also explain outbreaks of low pathogenicity avian influenza (LPAI) causing decrease in egg production in chicken layers and breeders. In the present study, 46-week-old specific pathogen free chicken layers were infected by the IN, IC or IO routes with one of two LPAI viruses: a poultry origin virus, A/chicken/CA/1255/02 (H6N2), and a live bird market isolate, A/chicken/NJ/12220/97 (H9N2). Only hens IN inoculated with the H6N2 virus presented mild clinical signs consisting of depression and anorexia. However a decrease in number of eggs laid was observed in all virus-inoculated groups when compared to control hens. Evidence of infection was found in all chickens inoculated with the H6N2 virus by any of the three routes, and the virus transmitted to contact hens. On the other hand, only 1 or 2 hens from each of the groups inoculated with the H9N2 virus shed detectable levels of virus or seroconverted, and did not transmit the virus to contacts regardless of route of inoculation. In conclusion, LPAI viruses can also infect chickens through other routes besides the intranasal route, which is considered the natural route of exposure. This has implications in the transmission and pathogenesis of AI viruses in poultry and can inform future management decisions for control of the virus.