Leukemia virus (FeLV) is found in cats worldwide, but the prevalence of infection varies depending on the cat's age, health, environment and lifestyle. Cats that are persistently infected with FeLV are the source of infection. The virus is shed in high quantities in the saliva and nasal secretions, urine, feces and milk of infected cats also contain virus. Cat-to-cat transfer of the virus can occur from a bite wound and during grooming, but rarely through contact with litter boxes and feeding dishes. The virus can be transferred from an infected mother cat to her kittens, either before birth or while they are nursing.
Feline leukemia occurs as primary and secondary viremia (viremia is when leukemia virus is present in the blood). Primary viremia is the early stage of infection. During this stage, a cat's body can adjust with an effective immune response, eliminate the virus from the bloodstream and stop progression to the secondary stage.
Secondary viremia, a later stage of infection, is a chronic infection of the bone marrow and other tissues and occurs if the cat's immune system fails to respond. When cat reach this stage, they will remain infected for the rest of their lives.
People are often worried they will be infected with leukemia from their cats. There are no studies to date that prove FeLV can be transmitted from infected cats to humans. However, FeLV-infected cats tend to carry other diseases, which can be zoonotic, or transmitted to humans, especially to people at risk. If my client is elderly, immune suppressed with AIDS or receiving chemotherapy, is pregnant or has an infant, I generally advise avoiding contact with FeLV-infected cats.
FeLV affects a cat's body in many ways and may not show any symptoms early in the disease. Over time, the cat's health deteriorates. It is the most common cause of cancer in cats, causing various blood disorders, and possibly leading to a state of immune deficiency.
Symptoms can be many and include loss of appetite and weight loss, poor hair coat, enlarged lymph nodes, persistent fever, pale gums, chronic inflammation of the gums and mouth, respiratory and bladder infections, chronic diarrhea, neurologic disorders, eye problems and abortion of kittens.
We commonly use an enzyme-linked immunosorbent assay or ELISA test in the clinic to screen cats for FeLV. This test will detect both primary and secondary viremia. A second test used in diagnostic laboratories is an IFA test, or indirect immunofluorescent antibody assay. The IFA test detects secondary viremia only, so if your cat is positive for this test, it will likely be infected for life. There will be times when it is suggested that the test needs to be repeated, depending on the cat's age and circumstances.
To prevent your cat from becoming infected, the best choice is to keep it indoors and away from infected cats. Only adopt cats that have tested negative for the virus. If you find you have an infected or FeLV-positive cat in your household, have your other cats tested, keep infected cats separately from infection-free cats, and do not allow them to share water bowls or litter boxes. Vaccinate infection-free cats; the vaccine does nothing for an infected cat.
Since not all vaccinated cats are protected, preventing exposure remains important for vaccinated cats. FeLV vaccines will not cause false positive results on any FeLV test.
Moreover, feed your cat with very nutritious food, avoiding any uncooked or non-pasteurized milk products, schedule exams every six months with blood counts and chemistries, and check the cat's weight. There are currently no proven immune stimulator or anti-viral drugs that have proven to be helpful.
Your FeLV-infected cat can remain in good health with good care for many months. Unfortunately, most infected cats die from a related disease within two to three years after becoming infected.
If you had an infected cat in your household that died, use precautions before bringing in another kitten or cat. The virus doesn't live outside the cat for more than a few hours in most environments, but FeLV-infected cats often have other infections. Clean bedding and food/water dishes, litter pans and toys with disinfectant and hot water. A diluted solution of four ounces of bleach in one gallon of water makes an excellent disinfectant. Vacuum carpets and mop the floors. Make sure new pets entering the house are properly vaccinated.
Sharon E. Anderson, DVM
