Feline immunodeficiency virus | |
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Virus classification | |
Group: | Group VI (ssRNA-RT) |
Order: | Unassigned |
Family: | Retroviridae |
Subfamily: | Orthoretrovirinae |
Genus: | Lentivirus |
Species: | Feline immunodeficiency virus |
Feline immunodeficiency virus (FIV) is a lentivirus that affects cats worldwide. From 2.5% up to 4.4% of cats worldwide are infected with FIV. FIV differs taxonomically from two other feline retroviruses, feline leukemia virus (FeLV) and feline foamy virus (FFV), and is more closely related to human immunodeficiency virus (HIV). Within FIV, five subtypes have been identified based on nucleotide sequence differences coding for the viral envelope (env) or polymerase (pol). FIV is the only non-primate lentivirus to cause an AIDS-like syndrome, but FIV is not typically fatal for cats, as they can live relatively healthily as carriers and transmitters of the disease for many years. A vaccine is available although its efficacy remains uncertain. Cats will test positive for FIV antibodies after vaccination.
FIV was first isolated in 1986 by Dr. Smith at the UC Davis School of Veterinary Medicine in a colony of cats that had a high prevalence of opportunistic infections and degenerative conditions and was originally called Feline T-lymphotropic Virus (FTLV). It has since been identified as an disease in domestic cat populations worldwide.
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, 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.
A vigilant pet owner who treats secondary infections can assist an infected cat to 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 existent risk.