Cat > Feline Immunodefiency Virus (FIV)
Information
Feline immunodeficiency virus (FIV) is a type of virus called a retrovirus. It is in the same family as feline leukemia virus (FeLV) and human immunodeficiency virus (HIV, the virus that causes AIDS). It attacks the immune system, and as a result, the cat is unable to fight off various infections and cancers.
Retroviruses are species-specific. This means a feline retrovirus like FIV will only infect cats; a human retrovirus such as HIV will only infect humans.
Retroviruses are made up of RNA. In the host, the RNA is transcribed into DNA and incorporated into the DNA of the host’s cells.
Retroviruses are fragile, being easily inactivated by ultraviolet light, heat, detergents, and drying.
FIV is NOT transmitted by prolonged close contact, as is the case for FeLV. FIV is shed in the saliva and is transmitted by bite wounds.
How common is FIV?
FIV is found worldwide in domestic cats, and also infects wild felines including snow leopards, lions, tigers, jaguars, Florida panthers, and bobcats. Although the virus was first isolated in 1987, we know the virus has existed for many years. It is most common in outdoor, free-roaming cats. In the United States, 1-8 percent of apparently healthy cats are infected with FIV.
Male cats are twice as likely to become infected with FIV as female cats. Free-roaming cats are also more likely to be infected since they too are more susceptible to bite wounds. Unlike FeLV, FIV infection is rare in catteries since few bite wounds would be expected in a cattery situation.
How does the virus cause disease?
FIV infection in cats has three stages, just like HIV infection in humans. The initial or acute stage of FIV infection is often characterized by fever, swollen lymph nodes, and a susceptibility to skin or intestinal infections. This stage generally occurs 4-6 weeks after being exposed to the virus.
The second stage is a latent or subclinical stage in which we see no signs of disease. This stage can last for many years. During this stage, the immune system may slowly be destroyed. When the immunodeficiency becomes severe, the third stage of infection occurs.
The third stage is the final or AIDS-like stage, and occurs most commonly in cats 5-12 years of age. (FeLV is seen most often in cats 1-5 years of age.) During this final, clinical stage, the cat's immune system is not functioning correctly since the virus kills essential cells in the system. Because of this, the cat is very prone to infections. These infections, which are usually chronic, may be bacterial, fungal, or parasitic. Often, they are caused by organisms which normally do not cause severe disease in cats. But since the immune system cannot keep them in check, they multiply rapidly and cause disease. These are called opportunistic infections.
We can see chronic upper respiratory tract infections, intestinal infections, and skin/ear diseases. Certain cancers may develop in some cats; researchers are determining how FIV is involved. Other cats may show neurologic signs although FIV generally has less effect on the nervous system of cats when compared to the effect of HIV in humans. Anemia can occur and may be a result of a parasitic infection. Once a cat is in the late stages of disease, life expectancy is 1 year or less.
What are the clinical signs of disease?
FIV-infected cats may show nonspecific signs such as lethargy, loss of appetite, fever, swollen lymph nodes (lymphadenopathy), and weight loss. The signs of FIV infection and FeLV infection are very similar.
Oral Infections: Chronic oral infections occur in approximately 50% of cats with FIV-related disease. Cats may show pain when touched on the face, have difficulty eating or refuse to eat, and may have a bad odor around the mouth. These infections can be difficult to control. Oral infections are more common in cats with FIV infection than those infected with FeLV.
Respiratory Disease: Approximately 30% of FIV-infected cats have chronic upper respiratory disease with sneezing and nasal discharge. These symptoms may be due to chronic infections with feline herpes (rhinotracheitis) or calicivirus. In some cats, pneumonia can develop and cause coughing and difficulty breathing.
Eye Disease: Along with signs of upper respiratory disease, cats may also show ocular signs such as redness of the eyes, discharge, and cloudiness of the cornea. Glaucoma is sometimes seen, as well.
Gastrointestinal Disease: Chronic diarrhea is seen in 10-20% of FIV-infected cats. It may be due to cancer, bacterial infection, parasitic infestation, or FIV itself.
Skin and Ear Infections: Recurrent or chronic infections of the skin and ears may be the first sign of an FIV infection. Because of the immunodeficiency, parasites, yeast and bacteria overgrow and cause symptoms such as hair loss, itching, and pustules. Demodectic and notoedric mange, which are unusual in healthy cats may be seen. Chronic ear mite infections and aggressive ringworm lesions have also been reported. Chronic abscesses can also occur.
Neurologic Disease: Changes in behavior, loss of house-training, and dementia can be seen in FIV-infected cats. These symptoms may be caused directly by FIV or by parasitic (Toxoplasmosis) and fungal (Cryptococcosis) infections, which occur more often in immunosuppressed animals.
Lymphadenopathy: Lymph nodes in the abdomen and other parts of the body are often enlarged.
Anemia: Anemia is observed in approximately 1/3 of FIV-infected cats. Mycoplasma haemofelis, formerly known as Haemobartonella felis, is a parasite of red blood cells that may be responsible for many of these cases.
Neoplasia: FIV-infected cats are 5 times more likely to develop lymphoma and leukemia than uninfected cats. The exact mechanism for this is unknown.
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