Testing – Feline Immunodeficiency Virus (FIV) & Feline Leukemia Virus (FeLV)

Part of Ireland's TNR Manual

How to Help Community Cats

Note the studies and statistics quoted in this page are American statistics. There are no meaningful Irish statistics on the prevalence of FIV/FeLV in Ireland, but we could assume the data would be proportionately similar.

Adapted for Ireland from Alley Cat Allies.

FIV and FeLV are incurable viruses that only infect cats. Humans cannot catch or transmit these viruses. Not all cats that become infected will develop disease.

Many veterinary spay/neuter clinics do not test feral cats for FeLV or FIV, because most enjoy excellent health and are no more likely to be infected with these viruses than owned cats. In fact, owned cats and feral cats contract FeLV and FIV at an equally low rate (about 4%).*

CATalyst does not support testing feral cats in a TNR programme for FIV and FeLV for multiple reasons:

  • The percentage of feral cats infected with either FIV or FeLV is low. Studies detected FeLV in 4.3% of cats; FIV in 3.5%. This is similar to the rate in owned cats. Several large-scale spay/neuter clinics in the US report only a 1-2% incidence of FeLV in the early years when every cat is tested.
  • Test results can be unreliable and can result in false positives. Cats testing positive should be re-tested at least 28 days after the cat's last possible exposure to the virus.
  • Spaying or neutering cats inhibits the spread of the viruses. Since spaying and neutering reduces or eliminates the primary modes of transmission, such as fighting and breeding, infected cats pose less risk to other cats.
  • Infected cats are often asymptomatic and can remain healthy with no sign of illness for many years or for their entire life; considering all factors, more cats likely die from having positive test results than die from FIV-related disease.
  • Testing is prohibitively expensive. The cost of testing (and often re-testing because of false positive test results) hinders the success of a spay/neuter program. The goal of the program is to spay or neuter as many cats as possible. Resources are best applied to spaying and neutering more cats. And, increasing the number of cats that are spayed or neutered decreases the incidence of virus transmission.
  • FIV tests do not differentiate between FIV infection and FIV vaccination. A positive test is likely to result in euthanizing vaccinated cats that are not infected.
  • CATalyst does not support the killing of healthy cats who test positive for FeLV and FIV. The American Association of Feline Practitioners agrees (see their guidelines here), recommending against routine euthanasia of healthy FeLV- and FIV-positive cats. VICAS, the Irish veterinary association, has made no statement as to their stance.

All cats showing signs of illness or injury should be trapped and taken to a vet for medical treatment.

"Prevalence of feline leukemia virus infection and serum antibodies against feline immunodeficiency virus in unowned free-roaming cat", JAVMA, Vol 220, No. 5, March 1, 2002

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Part of Ireland's TNR Manual

How to Help Community Cats