Feline immunodeficiency virus

Feline immunodeficiency virus (FIV), occasionally referred to as Feline or Cat AIDS is a lentivirus that affects domesticated housecats worldwide. Approximately 11% of cats worldwide, and about 2.5% of cats in the USA, are infected with FIV. More than 90% of African lions in some zoos tested positive for the virus. FIV differs taxonomically from two other feline retroviruses, feline leukemia virus (FeLV) and feline foamy virus (FFV). Within FIV, five subtypes have been identified based on amino acid sequence differences coding for the viral envelope. FIV is not a death sentence for cats, as they can live relatively healthy as carriers and transmitters of the disease for many years. A vaccine is available although its efficiency remains uncertain, and cats will test positive for FIV after vaccination.

FIV was first discovered in 1986 in a colony of cats that had a high prevalence of opportunistic infections and degenerative conditions, and has since been identified as an endemic disease in domestic cat populations worldwide .


The primary modes of FIV transmission are deep bite wounds and scratches, where the infected cat's saliva enters the other cat's bloodstream. FIV may also be transmitted from pregnant females to their offspring in utero. It must be noted that such claims that FIV is transmittable by simply "touching noses" have been discredited.

This differs from FeLV, which may be spread by more casual, non-aggressive contact, such as petting, since the virus is also present at mucosal surfaces such as those in the mouth, rectum, and vagina, so casual contact cannot be ruled out as a potential transmission cause.

Therefore, FeLV (feline leukemia virus) is often known as a "friendly cat disease" whereas FIV (feline immunodeficiency virus) is known as an "unfriendly cat disease."


Veterinarians will check a cat's history, look for clinical signs, and possibly administer a blood test for FIV antibodies. FIV affects 2-3% of cats in the US and testing is readily available. It should be noted that this testing identifies those cats that carry the FIV antibody, and does not detect the actual virus. Therefore, a positive test does not necessarily mean the cat is a carrier of FIV.

False positives occur when the cat carries the antibody (which is harmless), but does not carry the actual virus. The most frequent occurrence of this is when kittens are tested after ingesting the antibodies from mother's milk, and when testing cats that have been previously vaccinated for FIV. For this reason, neither kittens under 8 weeks, nor cats that have been previously vaccinated are tested.

Kittens and young cats that test positive for the FIV antibody may test negative at a later time due to seroreversion, provided they have never been infected with FIV and have never been immunized with the FIV vaccine.

Cats that have been vaccinated will test positive for the FIV antibody for the rest of their life due to seroconversion, even though they are not infected. Therefore, testing of strays or adopted cats is inconclusive, since it is impossible to know whether or not they have been vaccinated in the past. For these reasons, a positive FIV antibody test by itself should never be used as criteria for euthanasia.

Tests can be performed in a vet's office with results in minutes, allowing for quick consultation. Early detection helps maintain the cat's health and prevents spreading infection to other cats. With proper care, infected cats can live long and healthy lives.

The American Association of Feline Practitioners, an organization of veterinarians with a special interest in the health of cats, urges regular testing but not euthanasia of infected cats. Infected cats can live for years if diagnosed early and managed properly.


A vaccine for FIV is available, and was developed using isolates of two of the five FIV subtypes (or clades): A and D. The vaccine was shown to be moderately protective (82% of cats were protected) against subtype A FIV, but a later study showed it to offer no protection against subtype A. It has shown 100% effectiveness against two different subtype B FIV strains. Vaccination will cause cats to have positive results on FIV tests, making diagnosis more difficult. For these reasons the vaccine is considered "non-core", and the decision to vaccinate should be made after discussion with a veterinarian and consideration of the risks vs. the effectiveness.

Approved Treatment

In 2006, the United States Department of Agriculture issued a conditional license for a new treatment aid termed Lymphocyte T-Cell Immune Modulator. Lymphocyte T-Cell Immune Modulator is manufactured by T-Cyte Therapeutics, Inc. and sold by IMULAN BioTherapeutics, LLC.

Lymphocyte T-Cell Immune Modulator is intended as an aid in the treatment of cats infected with feline leukemia virus (FeLV) and/or feline immunodeficiency virus (FIV), and the associated symptoms of lymphocytopenia, opportunistic infection, anemia, granulocytopenia, or thrombocytopenia. The absence of any observed adverse events in several animal species, suggests that the product has a very low toxicity profile.

Lymphocyte T-Cell Immune Modulator is a potent regulator of CD-4 lymphocyte production and function. It has been shown to increase lymphocyte numbers and Interleukin 2 production in animals.

Lymphocyte T-Cell Immune Modulator is a single chain polypeptide. It is a strongly cationic glycoprotein, and is purified with cation exchange resin. Purification of protein from bovine-derived stromal cell supernatants produces a substantially homogeneous factor, free of extraneous materials. The bovine protein is homologous with other mammalian species and is a homogeneous 50 kDa glycoprotein with an isoelectric point of 6.5. The protein is prepared in a lyophilized 1 microgram dose. Reconstitution in sterile diluent produces a solution for subcutaneous injection.

Other Unapproved Treatments

FIV TREATMENT (Probably helps with FELV too) Helps strengthen immune system to fight the virus. Enables FIV cat to live longer. The effect likely to vary depending on state of cat’s immune system and present disease progression. As with most treatments, start as early as you can in the disease progression. Cellular Forte Max Inositol Hexaphosphate (IP6) Capsules Inositol Hexaphosphate (IP-6) is derived from soybeans, rice, sesame seeds, beans, legumes and cereals. IP-6 is a polysaccharide (long-chain sugar) found in fiber that has anti-oxidants. Agaricus Bio Capsules for Dogs and Cats Contains Beta Glucans from the Agaricus blasei mushroom. Beta glucans have the ability to stimulate macrophage activity which could help reduce the impact of viruses, bacteria and malignant cells. The proper does is 300 mg/day in one dose. Agaricus Liquid Liquid form of Agaricus Bio. The dosage is One drop per pound/day. Milk Thistle Helps prevent depletion of glutathione, raises glutathione levels up to 35 percent and protects the liver from damage. It can be used in pets on chemotherapy to help the liver process and detoxify drugs. T-Cyte Terry Beardsley, Ph.D., is the researcher and the driving force behind this recently FDA approved product. The active protein in this injectable product serves as a growth factor to restore lymphocytes which are depressed by retroviral infections.


FIV can attack the immune system of cats, much like the human immunodeficiency virus (HIV) can attack the immune system of human beings. FIV infects many cell types in its host, including CD4+ and CD8+ T lymphocytes, B lymphocytes, and macrophages. FIV can be tolerated well by cats, but can eventually lead to debilitation of the immune system in its feline hosts by the infection and exhaustion of T-helper (CD4+) cells.

FIV and HIV are both lentiviruses; however, neither can infect the other's usual host: humans cannot be infected by FIV nor can cats be infected by HIV. FIV is transmitted primarily through saliva (bites), such as those incurred during territorial battles between males. Cats housed exclusively indoors are much less likely to be infected, provided they do not come in contact with infected cats.

Consensus whether there is a need to euthanize FIV infected cats has not been established, although this is a pragmatic approach towards protecting the general population and is a wise option for cats testing positive turned in to animal shelters. The American Associations of Feline Practitioners, as well as many feral cat organizations, recommend against euthanizing FIV+ cats, or even spending funds to test for the virus, as spaying or neutering cats seems to effectively control transmission - as neutered cats are less likely to engage in territorial fights. A vigilant pet owner who treats secondary infections can assist an infected cat live a reasonably long life. The chance that an FIV infected cat will pass the disease on to other cats within a household remains, and increases with serious fighting or biting . There is a quantifiable risk that cats living outside of a home can spread the disease to others and can also spread the disease in a group setting in a shelter. Cats living alone as a single pet, rarely left to roam free, pose a diminished, but not non-existent risk.

The disease occurs in three stages: First is the Acute Stage (1-2 months after transmission) in which fever, depression, and generalized lymphadenopathy are observed . Second is the Subclinical Stage (4 weeks to X months after transmission), in which symptoms of the disease decrease or disappear; however, all cats remain viremic for life. Third is the Chronic Stage, in which cats eventually succumb to chronic infections due to suppressed immune system function. Cats may incur stomatitis, odontoclasia, periodontitis, gingivitis, rhinitis, conjunctivitis, pneumonitis, enteritis, and dermatitis in the later stages of infection. FIV+ cats are less likely to develop AIDS-like symptoms than HIV+ humans.

FIV infects other feline species, and in fact is endemic in some large wild cats, such as African lions. Unlike domestic cats, these species do not necessarily exhibit symptoms, perhaps because they have developed evolutionary mutations that confer resistance.

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