Hepatitis In Dogs And Cats
Ron Hines DVM PhD
This article is now mostly a stub to take you to other, newer and more detailed liver-related articles and others regarding health issues that could affect your dog or cat’s liver. If you have a cat and your veterinarian has told you that they suspect cholangiohepatitis, go here. If your vets suspect your cat has hepatic lipidosis, go here. If your veterinarian believes your dog has a portosystemic liver shunt problem, go here. If they suspect hepatic microdysplasia go here. If they believe your pet’s mental decline is due to hepatic encephalopathy go here. If your dog or cat’s liver tests are abnormal, go here and here to look up the specific tests and the various reasons they might be high. When hepatitis is a complication of your dog catching leptospirosis go here. When liver issues might be a complication of your cat catching toxoplasmosis go here.
Hepatitis is an inflammation of the liver. In can occur suddenly or be a long-standing process of decline (chronic). Your pet’s liver is a very complex organ with many functions. It processes nutrients soon after they are absorbed through your pet’s intestines. One of its jobs is to detoxify compounds that have been eaten. That is why it is the first organ to come in contact with toxins and harmful products absorbed from your pet’s foods. That is also why it is often the organ most affected when dogs and cats react badly to medications.
Your pet’s liver also plays a major role in metabolism, energy storage and blood protein synthesis. It also produces bile, which aids in your pet’s digestion of food. It is quite common for both the liver and the bile-storing gallbladder to be affected simultaneously. Your pet’s liver has a very large reserve capacity – so it has to be severely damaged before signs of illness become apparent to pet owners.
The following information relates to some of the more common causes of hepatitis in dogs and cats – there are many more, less-frequent, causes that I do not discuss here. You will find better and more thorough discussions of the cause and treatment of some of those forms of liver disease through the links at the top of this article.
How Might My Veterinarian Diagnose Liver Disease In My Cat Or Dog?
Until liver problems are quite advanced, the signs of the disease can be vague and non-specific. They are often accompanied by weight loss (although in advanced cases, dogs and cats can actually weigh more due to the fluid that accumulates around a malfunctioning liver). In sudden liver damage, such as the ingestion of toxins, the liver is often enlarged. Enlarged livers also occur when cancers, particularly lymphoma, have invaded the organ. A key to diagnosing liver disease in your dog or cat is to measure the level of liver enzymes that are circulating in your companion’s blood. The most common enzyme to elevate in lever disease is ALT. Elevated ALT tells your veterinarian that your pet has liver damage, but it does not tell him/her much about the specific damage that has occurred. Other enzymes that are often elevated in hepatitis are AST and AP (alkaline phosphatase). A metabolite called bilirubin is often also be elevated, and your pet’s blood albumin might be low. You can read the normal values for those and other tests here. When any of those compounds are suspiciously high without explanation, your veterinarian will probably perform or request an ultrasound examination. During that examination, the veterinarian performing it may suggest they remove a very small piece of liver tissue (a biopsy) through a needle directed into the liver through ultrasound directed guidance. From that biopsy, a veterinary pathologist can determine the type of liver damage present. The pathologist’s interpretation of what is going on in your pet’s liver is very important for your veterinarian in developing the most appropriate treatment plan.
Infectious Canine Hepatitis Of Dogs (ICH, CAV-1)
Infectious canine hepatitis was once high on the list of causes when a veterinarian suspected liver disease in your dog. However, effective, long-lasting vaccines have made the disease uncommon. It is caused by a virus that is part of a group of similar virus called adenovirus (in this case, CAV-1). This disease is not infectious to people or cats, but foxes, wolves and bears can also catch and carry it. Dogs catch this disease by sniffing or ingesting the virus when it is present in the urine, nasal discharge, eyes and other secretions of infected dogs. Dogs can carry and pass on the virus for up to a year after recovering. Canine Adenovirus is part of the vaccine combinations your puppy receives when it is 12 -16 weeks old. Although the virus in the vaccine is Canine Adenovirus 2, it protects against type 1 as well. The canine adenovirus-1 does not only affect your dog’s liver, symptoms often include a cough, fever, depression and lack of appetite and occasionally neurological signs. (read here)
After entering the blood stream, this virus attacks the cells of the liver, eyes, kidneys and the inner linings of blood vessels throughout the body. Thankfully, most cases of CAV-1 are not that serious. The pets show few, generally mild, symptoms and recover spontaneously. In other dogs, only a cough develops. In these mild forms, dogs simply lose their appetite, or act mopey and run a low fever for a few days. But one or two weeks later, a few develop a temporary bluish discoloration of the cornea of their eyes called “blue eye”.
It is believed that dogs that recover from ICH are immune to the disease for the rest of their lives (at least no case of a second infection I know of has ever been reported). But a few unvaccinated puppies do become severely ill when they catch infectious canine hepatitis. Those pups can develop liver disease, internal bleeding, tonsillitis, and inflammation of the mouth and eyes. Those severe cases have been known to lead to shock and death.
After the virus gains entry into the dog, it localizes in the cervical lymph nodes and tonsils before traveling throughout the body. It generally takes approximately five days for the infection to become apparent to the owners. By that time, symptoms relate to the virus being in the liver, eyes, kidneys, brain and lungs. Infected dogs shed the virus in their stool, saliva and urine. The course of ICH is quite variable. As I said, most cases are mild. But over the next few weeks, some severely affected dogs will go on to develop chronic hepatitis and cirrhosis of the liver or even die. A few dogs will develop chronic kidney disease (pyelonephritis), glaucoma or circulatory and blood clotting abnormalities (vasculitis & DIC).
Once a dog has become infected with the CAV-1 virus, there is no current treatment that will destroy the virus. The best your veterinarian can do is to support the dog with good nursing care, intravenous fluids and medications and nutrients to lighten the workload of its liver. Antibiotics are usually also included in the treatment plan to prevent secondary infections. Despite what Zoetis and other pharmaceutical companies say about the desirability of yearly vaccination boosters, after receiving this vaccination at 12 and 16 weeks of age, your dog will be immune to CAV-1 and CAV-2 for many years – probably for life. Yearly booster vaccinations are unnecessary. Read about that here. Because of the effectiveness of these vaccines, cases of Canine Infectious Hepatitis/ICH have become quite rare in dogs in the United States and Europe.
Leptospirosis In Dogs
Very few cats are diagnosed with leptospirosis. That is odd, since rodents are a cat’s common prey. (read here) But when dogs catch leptospirosis, along with kidney and other organ damage, sudden hepatitis occasionally occurs as well. Read about leptospirosis in dogs here.
Chronic Active Hepatitis (CAH)
This disease is sometimes called Chronic Canine Inflammatory Hepatic Disease. Chronic active hepatitis is more common in dogs than in cats. It can occur in any breed of dog, male or female. CAH can occur at any age, although most of the pets that develop it are middle-aged or older. The fact that it is chronic means that the disease has been going on for weeks or months as opposed to acute forms of hepatitis.
In CAH, continuous liver inflammation and cell death eventually lead to the replacement of the pet’s normal liver tissue with scar tissue (cirrhosis). In many cases the exact cause of your pet’s problem will remain unknown.
Certain breeds are predisposed to CAH, these include Bedlington Terriers, Doberman Pinschers, Skye Terriers, Standard Poodles, Cocker Spaniels and West Highland White Terriers. In many of these pets, copper is found in excessive quantities in their liver. Other diseases that can lead to chronic active hepatitis are infectious canine hepatitis, leptospirosis, autoimmune disease and drug and chemical toxicities. Aflatoxins found in moldy grain (especially corn) can cause this disease as well. High-quality pet food manufacturers screen the grains they use for these toxins. Even grain-free dog and cat diets can contain aflatoxins in the non-grain carbohydrate sources they contain. You can read about some of the problems associated with these high-corn-content products here.
A study of chronic hepatitis in English springer spaniels in the UK found that it occurred at a younger age in that breed and with increased frequency in female dogs. No infectious cause could be found, and the authors suggest that, perhaps, many cases of chronic hepatitis in this dog breed are a form of autoimmune disease. (read here)
What Are Some Of The Signs of Chronic Active Hepatitis?
Symptoms of chronic active hepatitis are quite variable because your pet’s liver does so many things. The most common signs are increased lethargy, loss of appetite and diarrhea. These pets often drink and urinate more. As the disease progresses, many cases develop a swollen abdomen that is filled with fluid (ascites), low serum albumin protein levels and yellowish gums, eyes and skin (= icteric = jaundiced). In some cases, failing livers affects the pet’s nervous system. They become obtuse or appear blind. Read about that form of liver failure here. It can progress to seizures, coma and death.
How is Chronic Active Hepatitis Diagnosed?
Diagnosis relies on blood chemistry results that show an increase in the level of hepatic enzymes and on biopsies of the liver that show abnormal structure. Physical examination of your dog or cat can suggest the disease when jaundice is present; but there are many non-liver explanations for jaundice as well. Pets with chronic active hepatitis generally have smaller than normal livers. That can be often seen on x-rays and ultrasound images your veterinarian obtains. The texture of the liver seen in those images also changes when serious cirrhosis is present.
How Can My Dog Or Cat Be Helped?
Treatment of cirrhosis is quite difficult because we have no medicines as yet to encourage regeneration of the liver. Hospitalized dogs usually receive intravenous fluids and general supportive care. We often place them on antibiotics, anti-inflammatory agents and lower protein diets. Veterinarians market various “liver support” medications but none have been adequately tested for effectiveness.
Copper-Associated Hepatitis In Dogs
Although copper is an essential nutrient for your pet, too much copper accumulating in the liver is toxic. Your dog or cat is unlikely to be exposed to too much copper in its food. But genetic diseases exist that cause an excess of copper to accumulate in a pet’s liver. We know that problem is an occasionally inherited disorder in doberman pinschers, bedlington terriers, Labrador retrievers and dalmatians. (read here & here) The end result is liver cirrhosis. Diagnosis requires a liver biopsy. Veterinarians attempt to disease is treated with medications (chelators) that bind with excess copper and allow its excretion from the body. D-penicillamine is generally the chelator of choice along with low copper/high zinc diets. Read more about those special diets here. Similar liver problems involving the metabolism of copper have been identified in Westies, Skye terriers.
Hepatitis Of Unknown Origin
Even the most thorough veterinarians or referral specialists can’t always give you a reason why your dog or cat developed liver disease. Hepatitis of unknown origin (= idiopathic) hepatitis or periportal hepatitis is sometimes diagnosed in dogs and cats. When it occurs, it is most common in pets in that are middle-aged. All breeds and both sexes appear equally susceptible. Signs include vomiting, diarrhea, weight loss, jaundice, ascites, depression and weakness as well as increased thirst and urination. Laboratory tests usually show an increase in the liver enzymes ALT and AP as well as increases in bilirubin, bile acids and globulin and a decrease in blood albumin and red blood cell numbers. Veterinarians treat these forms of liver damage with supportive care, antibiotics, lower-protein diets and sometimes immunosuppressants. How the disease progresses or resolves depends on the amount of functional liver tissue that can be saved.
Hepatic Lipidosis In Cats
This is a disease of cats. It occurs when your cat will not eat for a variety of health or environmental reasons. You can read considerably more about hepatic lipidosis here. Cats that are affected are often overweight. They may have stopped eating because of a change made in their diets or because of a stressful situation at home – such as moving, kenneling or health problems affecting their owners. Secondary hepatic lipidosis also occurs in cats that suffer from diabetes, intestinal disease, pancreatitis or any other serious systemic disease. Read about pancreatitis in your cat here. Many of those underlying conditions fall in the group I call triaditis. You can read about triaditis/cholangiohepatitis here. No mater what the cause of this problem, all cats develop an over-accumulation of triglycerides (fat) within their liver which blocks their normal liver activity. Signs of this disease include weight loss, vomiting, diarrhea, listlessness, drooling and jaundice. Laboratory tests often reveal elevated liver enzymes. In treating this condition veterinarians try to address any underlying health issues in order to get the cat to eat normally. Until this is done, cats often need to be hospitalized and tube-feed energy-rich, high caloric foods.
You are on the Vetspace animal health website
Visiting the products that you see displayed on this website help pay the cost of keeping these articles on the Internet.