Feline Immunodeficiency Virus (FIV)
Overview of Feline Immunodeficiency Virus (FIV)
Feline immunodeficiency virus (FIV) is a viral infection that attacks the immune system of cats. It is also known as Feline acquired immunodeficiency syndrome (Feline AIDS) and commonly referred to by the letters “F-I-V”. The immunodeficiency caused by the virus can promote a variety of symptoms including: infections caused by the poorly functioning immune system, anemia and low blood-cell counts, infections of the gums and mouth, cancer or neurologic disease.
Below is an overview of Feline Immunodeficiency Virus (FIV) followed by in-depth information about the diagnosis and treatment of this disease.
FIV is a retrovirus similar to the Human Immunodeficiency Virus (HIV also known as AIDS). FIV is not contagious to people; it is an infectious disease spread from cat to cat, primarily by biting and scratch wounds. FIV has been found in the mother’s milk and can be transmitted from mother to kitten. Experimentally, FIV can also be transmitted through semen however this is not thought to be a significant method of transmission in nature. Transmission among household cats through normal contact is thought to be unlikely. Outdoor, adult, and male cats are predisposed. Male cats are twice as likely to be infected as female cats. Adult cats are more common infected than kittens.
FIV has three stages of infection. They include an acute phase associated with various symptoms, which includes infections, fever and lymph node (gland) enlargement. The second phase is called the subclinical phase, which lasts from months to years, during which time many cats appear healthy and shows no clinical signs. The third phase is chronic infection, also known as the terminal phase, which is associated with deterioration of the immune function and that predisposes cats to a variety of infections. Clinical signs of the terminal phase are determined by how the virus affects the individual cat. Signs can be secondary to infections, tumors or neurologic dysfunction.
Infection is thought to involve between one and 14 percent of the cat population. In the United States, the prevalence is 2.5% to 6% in client owned cats and 3.5% to 23 % in stray cats.
Cats with FIV are more susceptible to stomatitis, upper respiratory tract infections, co-infection with feline leukemia virus (FeLV), toxoplasmosis, feline infectious peritonitis (FIP) and fungal infections.
What to Watch For
Many cats are diagnosed on a routine blood screening and are asymptomatic. If the FIV is causing active infections, sign will vary depending on the secondary problem caused.
Nonspecific signs of lethargy, anorexia, weight loss, depression or those associated with an infection can be seen. Infections can occur to any site including the skin, respiratory tract, neurologic system, eyes, mouth, and/or intestines.
Neurologic dysfunction can cause clinical signs of trouble walking, weakness, difficulty using a leg, seizures, and/or behavioral changes.
Diagnosis of Feline Immunodeficiency Virus
Veterinary care should include diagnostic tests and subsequent treatments. Diagnostic tests are needed to recognize FIV and exclude other diseases. Tests may include:
- Complete medical history and physical examination
- Blood test called the Enzyme-lined immunosorbent assay (ELISA) test should be done. The ELISA detects anti-FIV antibodies in the serum or saliva.
Results can be difficult to interpret in cats less than six months of age because some cats may still carry antibodies from their mother that is positive for FIV without actually being infected. These antibodies are generally gone from kitten by 6-months of age.
These tests will also be positive if the cat has been vaccinated for FIV. For this reason, only unvaccinated cats should be tested and every cat should be tested before the first FIV vaccination.
All positive test results should be confirmed with a second test called the Western blot or Polymerase chain reaction (PCR) test. Feline leukemia testing should also be completed to determine if this infection also exists.
Treatment of Feline Immunodeficiency Virus (FIV)
There has been no proven cure for FIV infection, several treatment options, supportive care, and symptomatic therapies are important, including:
- Antibiotics for bacterial infections
- Nutritional support
- Parasite control
- Keeping the cat indoors and isolated from other cats
- Biopsy and removal of tumors
Administer prescribed medications and monitor your cat’s general activity level, body weight, appetite and attitude. Provide quality nutrition and schedule veterinary visits to monitor the condition.
Keep all FIV infected cats indoors to decrease exposure to other cats. It is ideal to isolate FIV infected cats from negative cats, however, as mentioned earlier transmission among household cats through normal contact is thought to be unlikely although it is possible.
For cats with FIV, preventative health care and dental care with antibiotic coverage prior to the procedure is often recommended in infected cats. Vaccination for other diseases should be discussed with your veterinarian. If yearly vaccinations are given, only killed vaccines, which are vaccines made up of killed virus, as opposed to other types where live virus may have been modified, should be utilized to protect a potentially inadequate immune system in infected cats.
Feline immunodeficiency virus is an infectious disease that can be prevented primarily by eliminating interactions with infected cats. Keeping your cat indoors is the most effective way to prevent FIV. Test all new cats prior to bringing them into your home and exposing them to your other cats. Recently, a vaccine has been developed that can help reduce the risk of acquiring FIV in at-risk cats. This is most beneficial in indoor/outdoor cats, outdoor cats or cats exposed to many new cats.
Other prevention methods include to neuter males (to minimize or prevent fighting). It is also recommended to isolate, test and treat infected cats.
In-depth Information on Feline Immunodeficiency Virus (FIV)
Other medical problems can lead to symptoms similar to those encountered in feline immunodeficiency virus. It is important to exclude these conditions before establishing a diagnosis of FIV infection. These conditions include:
- Ehrlichiosis, an infectious disease caused by unusual bacteria called rickettsia that live inside of white blood cells or platelets
- Rocky mountain spotted fever, an infectious disease caused by another rickettsial agent
- Feline leukemia virus (FeLV) infection
- Feline infectious peritonitis (FIP), a viral disease of cats
- Fungal infections such as cryptococcosis, histoplasmosis, blastomycosis and coccidioidomycosis
- Toxoplasmosis, an infectious disease caused by a protozoa that completes its life cycle in cats
- Hemobartonella felis, an infectious disease caused by a bacterial parasite that lives in red blood cells
- Leukemia, cancer of blood-forming tissues with spread of cancer cells through the bloodstream
- Lymphoma, solid tumor of the lymphoid tissues that produce lymphocytes
- Multiple myeloma, a tumor of the antibody-producing B-type lymphocytes
- Myeloproliferative disease, cancer of the white blood cell producing bone marrow tissue
- Other forms of cancer
- Sepsis, body wide infection caused by spread of bacteria or their toxins in the bloodstream
- Systemic lupus erythematosus, a disease in which the body’s immune system mistakenly recognizes certain body tissue components as foreign and attacks them.
Diagnostic tests must be performed to confirm the diagnosis of feline immunodeficiency virus and exclude other diseases that may cause similar symptoms. Some of the following diagnostic tests may be recommended:
- A complete medical history and a thorough physical examination. Special attention is paid to mucous membrane color and lymph node size.
- Blood test for feline immunodeficiency virus. The routine screening test is called the
Enzyme-lined immunosorbent assay (ELISA). The ELISA detects anti-FIV antibodies in the serum or saliva. As mentioned earlier, Results can be difficult to interpret in cats less than six months of age. These tests will also be positive if the cat has been vaccinated for FIV. For this reason, only unvaccinated cats should be tested and every cat should be tested before the first FIV vaccination.
If positive, a second test should be done to confirm FIV status using the Western blot or Polymerase chain reaction (PCR) test. The western blot test is considered to be definitive for FIV. If the initial screening test is positive but the western blot is negative, the cat is considered negative for FIV.
False positive ELISA tests can occur in cats less than 6 months of age that still have antiboidies from their mothers or from their mothers milk (maternal or colostral antibodies), in cats that have been vaccinated and a few from test error.
False negative ELISA tests can occur in cats that were recently infected and have not yet began to produce antibodies (it can take 8 weeks from exposure to have a positive test result). If you got your cat today and he is negative and he was exposed to a cat with FIV yesterday, it may be two months before he shows a positive test result. The other cause for false negative test results can occur in cats with end-stage FIV. These cats will have such severe immunodeficiency that their bodies will no longer make detectable antibody for the test.
- Blood test for feline leukemia virus (FeLV), because FeLV infection can cause similar signs to FIV infection.
- Blood test for feline infectious peritonitis (FIP).
- Serum tests for toxoplasmosis and ehrlichiosis.
- A complete blood count (CBC) to evaluate your cat for anemia, signs of inflammation and blood platelet numbers.
- A biopsy or fine needle aspirate, which is a sample collected by aspirating cells through a syringe and needle, of any solid tumors may be performed for microscopic analysis and diagnosis.
Your veterinarian may recommend additional diagnostic tests to exclude or diagnose other conditions and to better understand the impact of FIV infection. These tests ensure optimal medical care and are selected on a case-by-case basis and may include:
- Serum biochemistry tests to evaluate the general health of your cat and to determine the impact of FIV infection on other body systems such as the kidneys and liver. Serum biochemistry tests often are normal in cats with FIV infection.
- Urinalysis to evaluate kidney function and identify protein loss in the urine or urinary tract infection. Urinalysis usually is normal in cats with FIV infection, but occasionally unless urinary tract infection may be present.
- Thoracocentesis refers to the aspiration of accumulated fluid from the chest cavity using a needle and syringe. The fluid obtained is submitted for microscopic analysis to identify other diseases such as lymphosarcoma, pyothorax (bacterial infection in the chest cavity) or feline infectious peritonitis.
- Abdominal paracentesis refers to the aspiration of accumulated fluid from the abdominal cavity using a needle and syringe. The fluid obtained is submitted for microscopic analysis to identify other diseases such as FIP and spread of cancer to the peritoneal cavity.
- Chest X-rays may be taken if your cat has difficulty breathing or abnormalities are found on listening to the chest with a stethoscope. Chest X-rays may show evidence of secondary bacterial pneumonia in some cats with FIV infection.
- Bone marrow aspiration and microscopic analysis may be recommended in some FIV-infected cats with some combination of low white cell count, anemia, and low platelet count.
- Cerebrospinal fluid (CSF) analysis may be recommended in FIV-infected cats with clinical signs of nervous system disease. The CSF fluid also can be analyzed for the presence of antibodies against FIV, abnormally high numbers of inflammatory cells and high CSF protein concentration.
Treatment of FIV infection must be individualized based on the severity of the condition and other factors that must be analyzed by your veterinarian. If your cat has no clinical signs, no treatment may be necessary. In this situation, regular follow-up visits to your veterinarian are important to ensure the condition does not progress. If immunodeficiency and secondary infection have developed, additional treatment will be necessary. Supportive care and symptomatic therapy are important and include:
- Antibiotics for secondary bacterial infections
- Nutritional support
- Fluid therapy in dehydrated cats
- Parasite control
- Isolation from other cats that may have an infection
- Biopsy and removal of tumors
Several drugs that are used to treat people with human immunodeficiency virus (HIV) infection have been used in cats with FIV infection. Drugs used may include the following:
- Zidovudine (AZT®) is an antiviral drug (a nucleoside analog) commonly used in human patients with AIDS that also has been used in FIV-infected cats. Treatment with AZT may result in clinical improvement, immune function, and quality of life. AZT has some potentially serious adverse effects and should be administered to FIV-infected cats under the supervision of a veterinarian experienced with its use.
- Alpha interferon (Roferon®) may reduce viral replication in some infected cats. It is not licensed for use in cats, but some clinical studies found increased activity, increased appetite, improvement of blood abnormalities, increased clearance of virus and prolonged survival in treated cats.
- Immunomodulators could be beneficial in cats with FIV infection by restoring immune function. Examples include Propionbacterium acnes (Immunoregulin®) and Acemannan (Carrisyn®).
- 3TC (lamivudine) is another nucleoside analog used in human patients with AIDS that also has been used in some cats with FIV infection. Like AZT, its use is associated with potentially serious adverse effects and it should be administered to FIV-infected cats under the supervision of a veterinarian experienced with its use.
- 9-(2-phosphonylmethoxylethyl) adenine (PMEA) is another drug that has been used in FIV-infected cats and has been reported to reduce the severity of chronic mouth infections in affected cats.
- Bone marrow transplantation has been performed in a limited number of FIV-infected cats and is successful in restoring white blood cell counts in some instances. Infected cats, however, remain infected with FIV. This procedure is only available at a limited number of referral research institutions.
Prognosis for Cats with FIV
Most cats with FIV will live for months to years without symptoms. Most cats will eventually have enough viral replication that they will go into the terminal phase of the disease and develop secondary illness.
Follow-up Care for Cats with Feline Immunodeficiency Virus
Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow-up is crucial. Follow-up veterinary care for FIV often includes the following recommendations:
- Administer any medications by your veterinarian as directed.
- Contact your veterinarian promptly if you are having trouble treating your cat.
- Contact your veterinarian if your cat develops any new symptoms or if existing symptoms worsen.
- Carefully observe your cat’s appetite and general activity level. These are quality of life issues important to you and your cat.
- Examine and monitor your cat’s gum color, urination, defection, and lymph node size. Your veterinarian can show you where the superficial lymph nodes are located and how to palpate them.
- The FIV lives for only minutes outside the host. Common disinfectants such as soap based products eliminate the virus.
Use the “Test and Remove” program, which is a method to eliminate FIV-infected cats in a cattery or a multiple-cat household. The principles of this program are as follows:
- Do not bring any new cats into the household.
- Remove all FIV-positive, sick cats from the household.
- Quarantine all FIV-positive cats to one area in the household. They should have no contact with FIV-negative cats in the household.
- Disinfect all bedding, food and water dishes, litter pans, and toys. Bedding, food and food dishes, water bowls, litter pans, and toys used by FIV-positive cats never should be used by FIV-negative cats.
- Test all remaining untested cats in the household for FIV.
- Quarantine all FIV-negative cats to one area. Retest these cats in three months. If they are negative at that time, they are considered free of FIV.
- Quarantine and test all new cats that enter the household and isolate them from other cats in the household for three months. Re-test these cats after three months. If negative on re-testing, these cats are considered free of FIV.
- Cats are considered free of infection when two negative test results separated by three months have been obtained.
- Retest all FIV-positive cats. Cats that test negative for FIV after having testing positive on the first test should remain isolated. Re-testing should be carried out after 3 additional months.
- Actual follow-up depends on the severity of your cat’s disease, response to therapy, your veterinarian’s recommendations and your own views.
- There is now a vaccine available to help reduce the risk of acquiring FIV. Discuss the use of this vaccine in at-risk cats with your veterinarian. The use of the vaccine is controversial and is most often used with cats at high risk that are FIV negative.
Please note: Positive titers to FIV can occur from some vaccinations. This can produce a positive test result. If your cat tests positive to FIV and is NOT sick, please determine if your cat has been vaccinated recently. Titers to the vaccine can occur for up to 13 months after vaccination. Kittens born to vaccinated queens will also be positive to do passive transfer of antibodies.