Infectious canine hepatitis is a viral disease caused by the canine adenovirus CAV-1, a virus that causes upper respiratory tract infections. This virus targets the parenchymal parts of the organs like liver, kidneys, eyes and endothelial cells of the blood vessels.
The virus first houses in the tonsils after nose and mouth exposure and then spreads to the bloodstream – a condition know asviremia – and then deposits in the Kupffer cells (specialized white blood cells located in the liver) and endothelium of the liver. Ideally, these white cells, called macrophages, defend the body against infectiions, but some viruses have the ability to use macropahages as vehicles for replication and spread. CAV-1 is one such virus, taking advantage of the Kupffer cells to replicate and spread, in the process damaging the adjacent hepatocytes (liver cells that are involved in protein synthesis and storage, and transformation of carbohydrates). During this stage of the infection, the virus is also excreted into the feces and saliva, making them infectious for other dogs.
In a healthy dog with an adequate antibody response, the viral cells will clear the organs in 10 to 14 days, but will remain localized in the kidneys, where the virus will continue to be excreated in the urine for 6 to 9 months.
In dogs with compromised antibody response, chronic hepatitis takes place. This severe condition often results in cytotoxic ocular injury due to inflammation and death of the cells in the eye with inflammation of the front of the eye (anterior uveitis). This condition leads to one of the more outwardly visible and classic signs of infectious hepatitis: “hepatitis blue eye.”
There are no breed, genetic, or gender associations for acquiring the CAV-1 virus, but but it is primarily seen in dogs that are less than one year of age.
Symptoms will depend on the immunologic status of the host and degree of initial injury to the cells (cytotoxic):
Peracute (very severe) stage will have fever, collapse of blood vessels, coagulation disorder (DIC). Death frequently occurs within hours
Acute (severe) stage will show symptoms of fever, anorexia, lethargy, vomiting, diarrhea, enlarged liver, abdominal pain, abdominal fluid, inflammation of the vessels (vasculitis), pinpoint red dots, bruising of skin (petechia), DIC, swollen, enlarged lymph nodes (lymphadenopathy), and rarely, inflammation of the brain (nonsuppurative encephalitis)
Uncomplicated infection will have symptoms of lethargy, anorexia, transient fever, tonsillitis, vomiting, diarrhea, lymphadenopathy, enlarged liver, abdominal pain
Late stage infection will result in 20 percent of cases developing eye inflammation and corneal swelling