Feline immunodeficiency virus (feline AIDS) | Vets & Clinics

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Feline immunodeficiency virus (feline AIDS)

Feline immunodeficiency virus was first identified in the United States in 1986. The infection subsequently spread to the rest of the world.

Veterinary medicine and care

Feline immunodeficiency virus

Feline AIDS is caused by the feline immunodeficiency virus (FIV). It is a retrovirus (family Retroviridae) belonging to the Lentivirus subfamily.

Transmission of feline AIDS

In cats, feline AIDS is transmitted exclusively by bites. No other means of transmission have yet been identified. This singular mode of transmission means that most animals affected by the virus are semi-wild, adult entire male cats. Scientific studies conducted to date have not found any evidence that feline AIDS can spread to humans through bites or by any other routes.

Upon entering the body, FIV replicates in the lymph nodes nearest to the bite. From there it passes into the bloodstream, which leads to the viremic phase. At this stage the cat forms antibodies against the virus’ structural proteins p15 and p24 (nucleocapsid proteins) and gp40 (envelope glycoprotein), and may present transient signs of disease.

In subsequent years, the patient is seropositive for feline AIDS but remains asymptomatic. This is the period when cats can spread the disease. The patient will then gradually enter the immunodeficiency phase. Immunosuppression occurs because the virus selectively attacks and destroys CD4+ T-lymphocytes, thereby altering the CD4/CD8 ratio.

Clinical course of feline AIDS

Feline AIDS results in chronic and opportunistic infections. But this is not the only consequence of feline immunodeficiency virus. It also has a tropism for central nervous system cells, which can cause cortical lesions.

The acute infection phase can cause fever, diarrhoea, lymphadenopathy and neutropaenia. The chronic infection phase, that is, the immunodeficiency phase, provokes frequent chronic infections which respond poorly to routine treatments.

The most common infections during the course of feline AIDS, in order of frequency, are:

  • proliferative, ulcerative chronic gingivostomatitis
  • chronic upper respiratory infections
  • chronic pyoderma, subcutaneous abscesses and otitis
  • chronic enteritis and chronic lower urinary tract infections


The most common opportunistic infections associated with feline AIDS are:

  • haemobartonellosis
  • demodicosis
  • toxoplasmosis

Other symptoms caused by feline AIDS

Cats with feline AIDS may also have severe cachexia, fever of unknown origin, leukopaenia, nonregenerative anaemia and even glomerulonephritis due to chronic immune stimulation.

There is no cure for feline AIDS. The prognosis is poor. Once cats enter the terminal phase, they need to be euthanised as opportunistic diseases cannot be controlled.

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