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Facts About Feline Leukemia Virus

Feline leukemia virus (FeLV) is second only to trauma as the leading cause of death in cats, killing 85% of persistently infected felines within three years of diagnosis. The virus commonly causes anemia or lymphoma, but because it suppresses the immune system, it can also predispose cats to deadly infections. However, exposure to the feline leukemia virus doesn’t have to be a death sentence; about 70% of cats who encounter the virus are able to resist infection or eliminate the virus on their own.

How Feline Leukemia Virus Is Transmitted

Feline leukemia is a disease that only affects cats -- it cannot be transmitted to people, dogs, or other animals. FeLV is passed from one cat to another through saliva, blood, and to some extent, urine and feces. The virus does not live long outside the cat’s body -- probably just a few hours. Grooming and fighting seem to be the commonest ways for infection to spread. Kittens can contract the disease in utero or through an infected mother’s milk. The disease is often spread by apparently healthy cats, so any cat may transmit the virus even if it appears normal.

Your Cat’s Risk Factors

Exposure to infected cats raises your cat’s risk of contracting FeLV, especially for kittens and young adult cats. Older cats are less likely to contract the infection, because resistance seems to increase with age. For indoor-only cats, the risk of contracting FeLV is very low. Cats in multi-cat households or in catteries are more at risk, especially if they share water and food dishes and litter boxes.

Only about 3% of cats in single-cat households have the virus, but for cats that spend time outdoors, the rate is much higher. Still, the prevalence of FeLV has decreased over the last 25 years because of vaccines and reliable tests.

Symptoms of Feline Leukemia Virus

Cats infected with FeLV may exhibit one or more of the following symptoms:

  • Pale gums
  • Yellow color in the mouth and whites of eyes
  • Enlarged lymph nodes
  • Bladder, skin, or upper respiratory infections
  • Weight loss and/or loss of appetite
  • Poor coat condition
  • Progressive weakness and lethargy
  • Fever
  • Diarrhea
  • Breathing difficulty
  • Reproductive problems like sterility in unspayed female cats

Diagnosing Feline Leukemia Virus

Your veterinarian can diagnose the disease by conducting a simple blood test called an ELISA, which identifies FeLV proteins in the blood. This test is highly sensitive and can identify cats with very early infections. It is important to remember that some cats will manage to clear the infection within a few months and will subsequently test negative.

A second blood test, the IFA, detects the progressive phase of the infection, and cats with positive results for this test are unlikely to clear the virus. The IFA test is performed at a laboratory, rather than in your vet’s clinic. In general, cats that are IFA-positive have a poor long-term prognosis.

 

WebMD Veterinary Reference

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