Western
Meeting of Poultry
Clinicians and Pathologists
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Clinicians and Pathologists
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Inclusion Body Hepatitis in Broilers Less Than Two Weeks Old C. Riddell Western College of Veterinary Medicine University of Saskatchewan
Inclusion body hepatitis in broiler chickens in Saskatchewan has in the past occurred between 3-7 weeks of age and has been associated with immunosuppression due to early infection with infectious bursal disease. A reduction in incidence was noted subsequent to vaccination of broiler breeder flocks against infectious bursal disease. In 1997, two outbreaks of inclusion body hepatitis were diagnosed in younger broiler chickens. In both cases chicks came from outside Saskatchewan. In the first case, increased mortality was reported in 6 day old broilers. In these birds, livers were pale with a few petechiae in some. On histology multifocal to coalescing necrosis and large basophilic intranuclear inclusions were visible in livers. Similar multifocal necrosis and inclusion bodies were seen in one pancreas. No virus isolation was attempted, but electron microscopy revealed masses of viral particles suggestive of adenovirus. In the second case, increased mortality was noted in 13 day old broilers. Two hundred and fifty birds were lost over a period of 5 days on one floor of a barn on a farm, which housed a total of 42,000 broilers in two double-story barns, and one single-story barn. The dead birds had dark muscles and pale livers with petechiae. The bursae and thymuses appeared slightly smaller than normal. On histology multifocal necrosis and large basophilic intranuclear inclusion bodies were visible in livers. No significant pathology was noted in lymphoid organs. Virus isolation in embryos resulted in embryo mortality. An adenovirus was isolated in tissue culture. This adenovirus is presently being typed. There were no titers against infectious bursal disease and only on positive titer against chicken anemia agent in 10 bloods taken from the affected floor just prior to processing at 39 days of age. The mortality in very young broilers suggests that the outbreaks may be due to egg transmission of a pathogenic adenovirus. A similar disease pattern in broiler chickens due to fowl adenovirus of serotype 8, but not associated with infectious bursal disease or chicken anemia agent was recently reported in Australia. The disease was controlled in Australia by vaccinating broiler breeder replacements with serotype 8 fowl adenovirus. |
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