There are two distinct canine adenoviruses, canine adenovirus type 1 (CAV-1) which is mainly associated with infectious canine hepatitis canine adenovirus type 2 (CAV-2), which only seems to be associated with respiratory disease. Both types have been isolated from naturally occurring cases of respiratory disease, and experimentally both can induce mild respiratory disease if given by aerosol. However, CAV-2 is more commonly associated with respiratory disease than CAV-1.
Both viruses induce similar respiratory lesions with a necrotising bronchitis and bronchiolitis and focal necrosis of the turbinates and tonsillar epithelium
Although lesions are restricted to the respiratory tract, virus can be isolated from both respiratory tract and intestinal epithelium. The normal shedding time for CAV-2 is 8-9 days post infection: although virus can persist in the tissues of clinically recovered dogs for several weeks after infection, unlike in ICH this is probably not epidemiologically important.
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