INFECTIOUS CANINE HEPATITIS

BY SANA GHAFFAR,

DVM Student, FVS, UAF.

Hepatitis means inflammation of the liver. Your pet's liver is a very complex organ that processes nutrients soon after they are absorbed through its intestines. This makes it the first organ to come in contact with toxins and harmful products absorbed from your pet’s foods.

The liver plays a major role in metabolism, detoxification, energy storage and blood protein synthesis. It also produces bile, which aids in digestion. Your pet's liver has a very large reserve capacity - so it has to be severely damaged before any signs of illness will become apparent to you.

The following information relates to infectious canine hepatitis that is a condition that affects the liver and kidneys, causing inflammation of the organ tissue that in turn can lead to the development of fibroids, liver disease, jaundice, disorientation and changes in personality, bleeding disorders and lesions. In the later stages, it can affect many other organs, including the spleen and lungs as well. Understandably, infectious canine hepatitis is highly unpleasant for your dog, is painful, and can make them quite sick and even, in some cases, prove fatal.

Causative agent:Infectious canine hepatitis is caused by canine adenovirus-1 (CAV-1), which is found world-wide and can infect most canine species, although some, including the domestic dog, are more sensitive than others. The virus is relatively hardy and can survive for months in the environment under ideal conditions.

There is also a canine adenovirus type 2, which causes respiratory disease.

Species affected:

Infectious canine hepatitis is a rapid-onset and potentially fatal condition that can affect dogs of all ages, breeds, shapes and sizes. It can also affect and be spread by foxes, and in other countries where rather more exotic animals roam freely, coyotes, wolves and bears too.

Something interesting about CAV-1 :

Canine Adenovirus 1 invades via the oronasal route following excretion in the urine and faeces and spread via fomites. Once established, CAV-1 replicates in the cells of the oropharynx before a viraemia causes dissemination to other tissues 4-8 days later.In the liver, CAV-1 replicates in Kuppfer cells and damages adjacent hepatocytes when released. Other parenchymal organs, namely the kidney, and the eye may also be affected in infectious canine hepatitis. When an adequate antibody response is mounted, organs may be cleared of virus within 10-14 days, but urinary excretion can persist for up to nine months after an active infection.

In the liver, the clinical outcome of CAV-1 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 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. In the kidney, virus localisation or deposition of circulating immune complexes causes glomerular damage and thus proteinuria. Immune complexes may also be deposited in the cornea and uveal tract, damaging the eye. In addition to glomerular localisation, CAV-1 persists in the renal tubular epithelium which accounts for the extended period of urinary excretion. Virus replication in the vascular endothelium leads to vasculitis and bleeding diatheses, and direct cytoxic damage to the eye is also possible.

Transmission:

Infectious canine hepatitis is highly infectious to other dogs, because it can be transmitted in a wide variety of ways.

> Infectious canine hepatitis is not an airborne disease, but it is present in the faeces, blood, saliva and urine of affected dogs, so directly touching the snout or back end of another dog that is suffering from or carrying the condition it can be transmitted.

>The virus that causes the condition is very virulent, and so your dog may even be able to contract the condition by contact with food or water bowls that have been used by an infected dog, as well as by other methods. It is important not to allow your dog to drink from any communal water bowls when out and about if at all possible; take a bottle of water and a dish with you when out on walks.

> Furthermore, dogs that have recovered from this disease can still be infectious to other dogs for more than six months.

> Young puppies are particularly susceptible to the disease.

What type of dogs are most at risk?Any unvaccinated dog can contract the disease, Unvaccinated dogs under one year old are the most likely to contract the condition and be worst affected by it, although the disease can affect dogs of any age.

Incubation period:The incubation period of infectious canine hepatitis is 4 to 7 days.

Clinical signs:Infectious canine hepatitis can be very quick in its development, and usually presents itself as an acute condition. Signs and symptoms to watch out for include:>Sickness and vomiting >Coughing>Cuts and small grazes not clotting properly>Cloudy eyes >Drinking and peeing a lot>Loss of appetite or disinterest in food>Light colored poop>Pain or enlargement of the abdomen>Pale gums and tongue

>Sudden weight loss Post mortem:

The liver is enlarged and friable on post-mortem examination.

>Extensive centrilobular necrosis leads to a pale, mottled appearance, but widespread haemorrhage is also apparent. These haemorrhages are particularly obvious on the serosal surface.

>This hepatitis leads to ascites, and fibrinous or fibrino-haemorrhagic adhesions can sometimes be seen between the lobes of the liver.

>Other organs may also show changes. For example, the wall of the gall bladder may be oedematous, and lymph nodes can be enlarged, reddened and haemorrhagic.

> In chronic cases, the liver may be small, fibrotic or cirrhotic.

>Histopathology reveals centrilobular necrosis. Haematoxylin and eosin staining reveals basophilic intranuclear inclusion bodies in hepatocytes and macrophages.

Diagnosing ICH-1:

In order to definitively diagnose infectious canine hepatitis, vet will run a variety of tests, including:

>blood tests,

>antibody tests and

>possibly immune-fluorescence scanning.

Treatment:

Infectious canine hepatitis is a severe and sometimes fatal condition, but surprisingly, it does often resolve itself and in mild cases, go away on its own as the body develops the necessary antibodies to fight off the virus.

Because the condition is usually acute and can potentially be fatal, however, veterinary intervention and treatment is usually recommended. This may consist of various different treatment methods, including a combination of some of the following treatment protocols:

>IV fluid therapy and inpatient monitoring

>Broad-spectrum antibiotics may be administered to kill the virus

>In serious cases and if available, a blood transfusion may be considered

>Reactive treatment to minimise the pain and discomfort of the condition, such as painkillers and creams to treat problems with the eyes.

Prognosis: Peracute cases carry a very poor prognosis and die within hours. The prognosis for acute cases is variable from guarded to good. It is also possible that recovered patients may develop chronic renal or hepatic disease.

Vaccination:A vaccine is available for infectious canine hepatitis and is a "core" canine vaccine. Thevaccine is a modified live strain of CAV-2, which confers cross-protection against CAV-1. The primary course consists of two vaccinations given three to four weeks apart, and boosters are required at least every two to three years.

Prevention:Infectious canine hepatitis can almost always be prevented by vaccination against the canine adenovirus. Most veterinarians recommend an initial “puppy series” of vaccinations, followed by a booster at one year and then boosters every 3 years thereafter, although specific vaccines and vaccination protocols can be controversial even within the veterinary community.

Can people catch infectious canine hepatitis?Infectious canine hepatitis is not a zoonotic condition, which means that it is not possible to catch the condition yourself from an affected dog. It is important to remember that you may carry the virus on your skin or clothes if you have been in contact with an affected dog, however, and could potentially pass it on to other canines that you meet.Conclusion:

Infectious canine hepatitis is a very contagious disease of dog that can cause inflammation of liver. It is not zoonotic but humans can be a source of its transmission if carry virus on skin and cloths. It is also transmitted by contact with water and food bowls of infected dogs (as by some other methods) so not allow your dog to drink in communal water bowls. Treatment is symptomatic and it is almost always be prevented by vaccination against the canine adenovirus.