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==Description==

==Description==

Infectious Canine Hepatitis (ICH) is a highly contagious disease of dogs caused by [[Canine Adenovirus 1]] (CAV1). This virus is closely related to Canine Adenovirus 2, which causes respiratory disease.

Infectious Canine Hepatitis (ICH) is a highly contagious disease of dogs caused by [[Canine Adenovirus 1]] (CAV1). This virus is closely related to Canine Adenovirus 2, which causes respiratory disease.

Canine Adenovirus 1 invades via the oronasal route following excretion in the urine and faeces. Urinary excretion can persist for up to nine months after an active infection, and the virus may also be spread by contaminated fomites. Once established, CAV1 replicates in the cells of the oropharynx before a viraemia causes dissemination to other tissues. A trophism exists for hepatic parenchyma and vascular endothelium: the target organs of CAV1 are therefore the liver, vascular endothelium, kidney and eye.

Canine Adenovirus 1 invades via the oronasal route following excretion in the urine and faeces. Urinary excretion can persist for up to nine months after an active infection, and the virus may also be spread by contaminated fomites. Once established, CAV1 replicates in the cells of the oropharynx before a viraemia causes dissemination to other tissues. A trophism exists for hepatic parenchyma and vascular endothelium: the target organs of CAV1 are therefore the liver, vascular endothelium, kidney and eye.

In the liver, widespread centrilobular necrosis occurs, which may progress to become panlobular. The clinical outcome of CAV1 infection is dependent on the level of pre-existing immunity. Animals with high antibody titres usually mount an effective neutralising antibody response by day seven post-infection which clears the virus. A partial antibody response withing four to five days post-infection can lead to chronic active hepatitis and ultimately hepatic fibrosis. Latent chronic hepatic infection is also possible. Low antibody titres, such as in unvaccinated dogs, fail to prevent infection and pathology, giving potentially fatal hepatic necrosis.

In the liver, the clinical outcome of CAV1 infection depends on the level of pre-existing immunity. Animals with high antibody titres usually mount an effective neutralising antibody response by day seven post-infection which clears the virus. Outcome is variable when a partial antibody response is mounted four to five days post-infection: both chronic active hepatitis (and ultimately hepatic fibrosis) and latent hepatic infection are possible. Low antibody titres, such as in unvaccinated dogs, fail to prevent infection and pathology and lead to potentially fatal hepatic necrosis. This necrosis is initially widespread and centrilobular, but may progress to become panlobular. 

Damage caused by localisation to the vascular endothelium can lead to vasculitis and bleeding diatheses such as disseminated intravascular coagulation.  

Damage caused by localisation to the vascular endothelium can lead to vasculitis and bleeding diatheses such as disseminated intravascular coagulation.