Response to West Nile Virus in Slaughtered Birds of the Order of Galliformes (Commercial Chickens, Turkeys, Guinea fowl, Pheasants, Quails), Rheas, Emus and Ostriches

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Although no natural infection or clinical signs of West Nile Virus (WNV) have been reported in domestic commercial poultry (Galliformes), and only sporadic cases of WNV infection have been reported in ostriches, the Canadian Food Inspection Agency (CFIA) will treat all situations where domestic birds show neurological signs as having the potential for hosting a foreign animal disease (FAD), such as Newcastle Disease (ND) or Highly Pathogenic Avian Influenza (HPAI). The CFIA will investigate them accordingly, as per appropriate FAD disease strategies.

Pathogenesis of West Nile Virus in commercial chickens and turkeys

Experimentally, WNV infected chickens and turkeys have not shown observable clinical signs of infection during the 21 days post infection (PI) observation period. Chickens tend to develop high level of viremia with virus titers as high as 105.0 /ml at fourth day PI, and WNV was isolated from blood plasma up to eight days PI. Turkeys however, develop viremia from 2 to 10 days PI, but the average level of viremia is low and the virus could not be isolated from plasma. WNV was also isolated from myocardium, spleen, kidney, lung and intestine collected from chickens at 3, 5 and 10 days PI; however no virus was isolated from chickens after 10 days PI. No virus was isolated from similar organs of infected turkeys. WNV does not cause gross pathological lesions in experimentally infected chickens and turkeys. After three weeks of age chickens appear to be resistant to natural WNV infection, thus commercial chickens reaching slaughter house at approximately 37-40 days of age should have passed the viremia stage and be free of virus in an unlikely event of being infected with WNV before three weeks of age.

Considering the remote possibility of natural WNV infection in chickens and turkeys, combined with experimental evidence that turkeys develop negligible levels of viremia and chickens are refractory to WN infections past three weeks of age, we can conclude that neither of those classes of poultry pose a risk of WNV transmission to humans.

Note: In 2002, the Wisconsin Division of Public Health (WDPH) investigated and found a high prevalence of WNV antibody among some farm turkey workers. Although, the mode of transmission to these workers remains unknown, the assumption was made that transmission by less typical routes might have occurred. Despite uncertainty, epidemiological evidence suggested that, in this particular situation, percutaneous injury or fecal-oral, or respiratory exposure to aerosolized-infected turkey feces could have caused human infection.

Other Galliforme slaughter birds (guinea fowl, pheasants and quails)

Limited research and indirect evidence suggests that the pathogenesis of WNV in these classes of poultry is similar to that seen in commercial chickens. There is no evidence that people become infected with WNV by handling these birds in a normal slaughterhouse environment.

Rheas, emus and ostriches

There is limited knowledge of natural WNV infection occurring in these birds, and only few cases of naturally occurring WNV infection in these species have been reported worldwide. To date, there have been no recorded cases of these birds passing WNV infection to other animals or to people.

Note: WNV is an immediately notifiable disease under the Health of Animals Regulations. All persons involved in the handling of these animals should follow occupational health and safety standards for handling slaughter animal species, as recommended in the document West Nile Virus - Protect Yourself! by Public Health Agency of Canada.

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