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Background

Feline immunodeficiency virus (FIV), commonly known as Feline AIDS is a lentivirus that affects domesticated housecats worldwide. According to Richards (Dec 2005:215-217), 11% of cats worldwide are infected with FIV. According to another study, 2.5% of cats in the USA are infected with FIV (Zislin Dec 2005, p. 219-220). FIV is in the same retrovirus family as Feline leukemia virus (FeLV). 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.[4]

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 (Johnson 2005).

[edit] Transmission

The primary modes of FIV transmission are deep bite wounds and scratches, and FeLV may also spread by more casual, non-aggressive contact, since the virus is also present in mucosal surfaces such as those in the mouth, rectum, and vagina, so casual contact cannot be ruled out as a potential transmission cause.

[edit] 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[1]. Lymphocyte T-Cell Immune Modulator is manufactured by T-Cyte Therapeutics, Inc. and exclusively 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.[2] It has been shown to increase lymphocyte numbers and Interleukin 2 production in animals.[3]

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.[4]

[edit] Effects

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. 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 (American Association of Feline Practitioners 2002). 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 (Wise 2005). 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 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.