Canine adenoviruses (CAdVs) consist of two types: type 1 (CAdV-1), which is the virulent strain, and type 2 (CAdV-2), which is the attenuated strain. Although they are difficult to distinguish when symptoms are atypical, there are some key differences between the two types.
Canine adenovirus type 1 (CAdV-1) is the cause of infectious canine hepatitis. It is historically recognized as a severe and often fatal disease of canids. Although uncommon, sporadic cases of CAdV-1 infection are still reported. Vaccination against CAdV-1 is necessary for the prevention of infectious canine hepatitis. Canine adenovirus type 2 (CAdV-2) cross-protects against CAdV-1, making it a core vaccine.
Canine adenovirus type 2 (CAdV-2) is related to the hepatitis virus, CAdV-1. It is used in vaccines to provide protection against canine infectious hepatitis. CAdV-2 is also one of the causes of infectious tracheobronchitis, also known as canine cough.
In summary, CAdV-1 is the virulent strain responsible for infectious canine hepatitis, while CAdV-2 is an attenuated strain used in vaccines to provide protection against canine infectious hepatitis and is also associated with infectious tracheobronchitis.