Feline Immunodeficiency Virus (FIV) stands as a globally prevalent and significant infectious disease affecting domestic cats. This virus targets the immune system, rendering infected cats susceptible to a wide array of secondary infections. While cats with FIV can appear healthy for extended periods, they eventually develop immunodeficiency, making them vulnerable to opportunistic infections from everyday bacteria, viruses, protozoa, and fungi that would typically be harmless. Despite the absence of a definitive cure for FIV, current research indicates that FIV-positive cats can often live full lifespans, particularly if they are not concurrently infected with feline leukemia virus (FeLV).
Understanding FIV Transmission and Risk Factors
The primary route of FIV transmission in cats is through deep bite wounds inflicted by an infected cat. Casual contact, like sharing food and water bowls or grooming, is considered an inefficient means of spreading the virus. Consequently, cats residing in stable, non-combative multi-cat households face minimal risk of FIV infection. Mother cats can, in rare instances, transmit FIV to their kittens, especially if the mother contracts FIV during pregnancy. Sexual contact is not considered a significant transmission pathway for FIV.
FIV is found worldwide, but its prevalence varies considerably. In North America, roughly 2.5-5% of healthy cats are infected. This rate significantly increases to 15% or higher in cats that are sick or at high risk. Due to the bite wound transmission, unneutered male cats with outdoor access, particularly those prone to fighting, are at the highest risk of acquiring FIV. Currently, there is no commercially available vaccine against FIV in North America. The most effective preventative measures include keeping cats indoors to limit contact with potentially infected cats and testing all cats within a household for FIV.
Clinical Stages of FIV Infection: Recognizing the Symptoms
FIV infection progresses through three distinct stages: the acute phase, the asymptomatic (or latent) phase, and the progressive phase.
The Acute Phase
The acute phase typically emerges 1-3 months post-infection. During this initial stage, the virus travels to the lymph nodes, where it replicates within T-lymphocytes, a type of white blood cell crucial for immunity. The virus then disseminates to lymph nodes throughout the body, causing temporary lymph node enlargement, often accompanied by fever, lethargy, and reduced appetite. This phase can be subtle and easily overlooked or misattributed to other common causes of fever in cats.
The Asymptomatic (Latent) Phase
Following the acute phase, cats enter an asymptomatic phase, which can last from months to years. During this latent period, the virus replicates slowly within immune system cells, and cats exhibit no outward signs of illness. Bloodwork might reveal subtle abnormalities, such as decreased white blood cell counts or elevated blood protein levels. Some cats may remain in this asymptomatic phase indefinitely and never progress to more severe disease.
The Progressive Immunodeficiency Phase
As FIV continues to weaken the immune system, cats enter a progressive immunocompromised state, making them increasingly susceptible to secondary infections. The majority of FIV-related illnesses stem not from the virus itself, but from these opportunistic infections or immune system dysfunction. Cats may develop chronic or recurring infections affecting the skin, eyes, urinary tract, or upper respiratory system. Gingivostomatitis, a severe inflammation of the gums and dental tissues, is frequently observed in FIV-infected cats. They also have a significantly higher risk of developing cancer and immune-mediated blood disorders compared to healthy cats. Other possible symptoms include weight loss, seizures, behavioral changes, and neurological disorders. The severity of these illnesses can vary widely, but once cats develop multiple severe infections or cancers, their survival time is often limited to a few months.
Diagnosing FIV: Antibody and PCR Testing
Determining a cat’s FIV status is crucial upon initial acquisition, if illness occurs, and regularly for cats at risk of exposure.
FIV diagnosis typically involves detecting antibodies against the virus in a blood sample. These antibodies develop as the cat’s immune system responds to the infection and persist throughout the cat’s life. The enzyme-linked immunosorbent assay (ELISA) test is commonly used and can be performed in veterinary clinics. Positive ELISA results are often confirmed with more specific tests like the Western blot or immunofluorescence assay (IFA) at a reference laboratory.
It’s important to understand that antibody tests detect the immune response to FIV, not the virus itself. This can lead to certain scenarios where a single test may not definitively determine a cat’s FIV status.
Interpreting FIV Antibody Test Results
A negative antibody test usually indicates the cat is not infected, as it means no FIV antibodies were detected. However, false negatives can occur in two situations:
- Early Infection: It takes 2-6 months for a cat to produce detectable antibody levels after infection. A recently infected cat may test negative even if truly infected. If recent exposure is suspected, retesting after at least 60 days is recommended.
- Late-Stage FIV: In rare cases, cats in the very late stages of FIV, with severely compromised immune systems, may test negative because they can no longer produce detectable antibodies.
A positive antibody test generally indicates FIV infection because antibodies persist once produced. However, false positives are also possible:
- Maternal Antibodies: Kittens born to FIV-infected mothers receive FIV antibodies through colostrum and may test positive up to six months of age. Most of these kittens are not truly infected. Kittens testing positive under six months should be retested every 60 days until they are at least six months old to clarify their status. A positive test after six months usually confirms true infection.
- FIV Vaccination: FIV vaccines, available in some countries outside North America (and discontinued in North America since 2016), cause vaccinated cats to produce FIV antibodies, leading to positive test results indistinguishable from natural infection. Vaccination history is crucial for interpreting test results.
PCR Testing for FIV
Polymerase chain reaction (PCR) tests detect FIV viral DNA directly, rather than antibodies. While PCR can be useful in specific situations, it’s not the preferred screening test due to a higher rate of false positives and negatives compared to antibody tests. PCR can be helpful as a confirmatory test in some ambiguous cases.
FIV Treatment and Management: Supporting Quality of Life
Currently, there is no cure for FIV. However, it’s crucial to understand that with proper management, FIV-positive cats can live long, healthy lives. Prognosis becomes less favorable once a cat develops severe FIV-related illnesses, persistent fever, or weight loss.
The primary management goals for healthy FIV-positive cats are minimizing the risk of secondary infections and preventing FIV transmission to other cats. Keeping FIV-positive cats indoors and separated from uninfected cats achieves both goals. Spaying or neutering prevents transmission through mating and reduces roaming and fighting tendencies if outdoor access occurs. A nutritionally balanced diet is essential, and raw food, eggs, and unpasteurized dairy should be avoided to minimize foodborne infections.
Regular veterinary wellness exams, at least every six months, are crucial. Veterinary check-ups include thorough physical examinations, focusing on gum, eye, skin, and lymph node health. Weight monitoring is important, as weight loss is often an early sign of health deterioration. Annual complete blood counts, serum biochemistry analyses, and urinalyses are recommended.
Close monitoring of an FIV-infected cat’s health and behavior is even more critical than for uninfected cats. Prompt veterinary attention is needed at the first sign of illness. FIV-positive cats may require extended or more intensive treatments for infections. Antibiotics may be recommended prophylactically for procedures like dental cleanings or surgery.
Treatment targeting the FIV virus itself is limited and primarily involves antiviral drugs developed for human HIV treatment. Zidovudine (AZT) can benefit cats with severe stomatitis or neurological disease but hasn’t been shown to extend overall survival and can have side effects. Ongoing research is exploring combination antiviral therapies for FIV.
Preventing FIV Infection in Cats: Key Strategies
Preventing exposure to the virus is the only definitive way to protect cats from FIV. Since cat bites are the main transmission route, keeping cats indoors significantly reduces their risk by limiting contact with potentially infected cats. When introducing new cats to a household, ensuring they are FIV-free is ideal. If FIV-positive cats must be integrated, separation from uninfected cats within the household is recommended when feasible.
In situations where FIV-positive cats have lived with other cats for extended periods before diagnosis, testing all cats in the household is essential. Ideally, infected cats should be separated from uninfected cats to eliminate transmission risk. However, in stable multi-cat households with minimal fighting, transmission risk is considerably lower.
FIV has limited environmental survival, lasting only a few hours. However, FIV-positive cats may carry other infectious agents. When introducing a new cat to an environment where an FIV-positive cat previously lived, thorough cleaning and disinfection or replacement of food/water dishes, bedding, litter boxes, and toys is prudent. A diluted bleach solution (four ounces bleach per gallon of water) is an effective disinfectant. Vacuuming carpets and mopping floors are also recommended. New cats should be appropriately vaccinated against other feline infectious diseases before entering the household.
FIV and Human Health: No Risk of Transmission
While FIV is related to HIV and causes a similar immunodeficiency syndrome in cats, it is highly species-specific and infects only felines. There is no evidence that FIV can infect or cause disease in humans. FIV poses no health risk to humans.
Last updated 2021
