Viral cat killers- The Invincible Triad

Many cat succumb to virus attacks every year. There are three major viruses responsible for the majority of cat fatalities worldwide: Feline Leukemia Virus (FeLV), Feline Immuno-deficiency virus (FIV), and Feline Infectious peritonitis Virus (FIP).

FeLV and FIV are viruses called Retroviruses. They attack the immune system, causing problems with the body defense mechanisms and consequent multi-system disease.

FeLV causes Feline Leukemia. Cats can develop two forms- neoplastic, which manifest in tumors involving various locations, and non-neoplastic, which manifest in infections and signs related to immunodeficiency. The disease is more common in outdoor cats and in multi-cat households. It is transmitted via saliva by bites or mutual grooming, and from mother to offspring. Signs include tumors in various sites, weakness, lethargy, weight loss and wasting, respiratory and digestive system infections, nervous system and eye problems. Affected cat receiving specific treatment may survive for a while, however the disease has no cure and is almost always fatal.

Every cat introduced into the house should be tested for the disease and quarantined prior to exposure to the other household cats. In households where there is exposure to outside cats, whether cats go outside or outdoor cats are introduced inside, every cat should be vaccinated against FeLV. Periodic screening in multi cat households is also advocated.

FIV causes a disease similar to AIDS in humans, and is being studied as a model for AIDS. The disease is clinically indistinguishable from the non-neoplastic form of Feline leukemia. The transmission occurs via bites and therefore male cats are at higher risk. Treatment modalities and prognosis are similar to those of Feline leukemia. There is no vaccine available and therefore keeping cats indoors is the only way of prevention. However a screening blood test can and should be done in a similar manner to FeLV.

Feline infectious peritonitis (FIP) is a deadly disease caused by a Virus called coronavirus. Many different strains of coronavirus commonly infect cats, but do not cause a serious disease. FIP-producing strains invade white blood cells and induce an intense immune mediated inflammation in different tissues. The virus is transmitted by inhalation or ingestion of saliva or feces directly or indirectly.

FIP is typically a familial or a community disease and it is thought that FIP strains are mutants of the less aggressive coronavirus that infect the population. That might explain, at least in part, why only some cats in the group will develop lethal FIP.

There are two forms of FIP- effusive (wet), noneffusive (dry). A combination of both is also seen. Effusive FIP is characterized by the fluid accumulation within the abdomen and/or chest and possible breathing difficulty. Signs tend to appear quickly (especially in kittens). The onset of noneffusive FIP is usually slower and may take months or even years. Cats may show intermittent fever, inappetence, and depression and develop rough hair coat and weight loss. Signs of kidney failure (increased water consumption and urination), liver failure (jaundice), pancreatic disease (vomiting, diarrhea, diabetes), neurologic disease (loss of balance, behavioral changes, paralysis, seizures), enteritis (vomiting, diarrhea), or eye disease (inflammation, blindness) may be seen in various combinations.

FIP is difficult to diagnose because signs mimic those of many other diseases. There is no specific test available, and currently we can only detect presence of coronavirus, which is very common in cats. The diagnosis is based on clinical signs, tissue and fluid analysis and other laboratory tests.

There is no cure for FIP and it is routinely fatal. Treatment is supportive and consists in suppressing the immune system, preventing secondary infections and treating the involved organ systems.

Multiple cat households, breeding catteries and shelters are at high risk of devastating FIP outbreaks. Ideally they should be kept free of coronavirus, which is often very difficult to accomplish. When this is not feasible, FIP vaccination should be done. In the real world, FIP is very difficult to eradicate once a colony is infected. The problem is especially severe in breeding colonies, where cats may develop FIP at any time, despite all preventative efforts.