Feline leukemia virus (FeLV) in cats

Cats with FeLV should be kept inside

There isn’t a more frightening diagnosis for a feline guardian than hearing their kitty has tested positive for feline leukemia virus (known as FeLV) or feline immunodeficiency virus (known as feline AIDS or FIV). As in the situation with dogs that test positive for Lyme disease, a cat who tests positive on an in-house veterinary ELISA lab test does not necessarily mean that the cat is clinically infected.

With feline leukemia virus, an IFA antibody test should always be done to confirm if a true positive result, and is often considered the gold standard of diagnosing FeLV infection. With FIV, a western blot is recommended, which is also done at an outside laboratory. As with people, many patients who test positive may not have any symptoms of disease, and with the case of FIV positive cats, these pets can often live long and healthy lives, as long as they are neutered/spayed and remain indoors and placed under as little emotional, physical or toxic stress that is possible. With true FeLV positive animals, the prognosis is somewhat different. I have often read statistics that say that up to 85% of true FeLV positive cats will die of a complication of FeLV infection within 3 years of diagnosis.

As with human AIDS, both of FeLV and FIV can suppress the immune system leading to many other clinical problems and infections. Common symptoms of illness include inflammation of the gums and mouth (sometimes to a very severe degree called gingivitis/stomatitis), chronic or recurring respiratory symptoms such as sneezing, nasal congestion and/or coughing, chronic or intermittent digestive or skin disorders, as well as tumors, both skin and internal tumors that can involve any organ system, but most commonly the lymph nodes in the cats’ bodies.

These are cats who in my opinion should be kept inside, minimally vaccinated for other diseases if they are kept indoors, other than rabies vaccination as required by law in many states. These cats should be on an all-natural diet, preferably home made, but if not possible then excellent natural commercial diets like Wysong or Pet Guard. In my practice I also recommend immune stimulants to boost the immune system of such cats. Such products as Vetri-DMG liquid and good multivitamins like VitaChews for Cats are essential. Other products I’ve used include Transfer Factor, Colostrum and extra vitamin C added to their diets. There are vaccinations for both of these diseases now available.

Because of my concern for safety and efficacy, as well as after discussing my concerns with the discoverer of the FIV virus, I do NOT recommend FIV vaccination. For cats who are freely roaming or spend a lot of time outside exposed to other cats, vaccination with one or two vaccinations of FeLV could be considered by a feline guardian. Before a guardian subjects their cat to yearly or over vaccination with FeLV, they should be made aware of a few facts. Most cats who become infected with feline leukemia virus acquire the virus under the age of one or two. In other words, there seems to be an age associated natural immunity to those cats who are older and who spend lots of time outside. Thus a 4 year old cat that is tested negative for feline leukemia is unlikely to acquire infection as they get older, even if they go outside.

Back when the first vaccination studies were done, the experimenters could not even induce disease in cats over the age of one or two when testing efficacy of the early vaccinations. And while many feline task forces and various feline political organizations recommend yearly vaccinations for cats that spend significant time outdoors and are exposed to wandering other cats, I personally do NOT recommend this practice due to the age acquired immunity most cats achieve. Also, like most viral vaccinations in dogs and cats, immunity to any vaccinations of younger cats over 4-5 months old for this virus probably lasts for years to the life of the pet.

Over the past 2 decades there has also been concern about cancers at the site of feline leukemia virus vaccinations, believed to occur in 1 in 5000 cats vaccinated. There have been newer vaccine delivery systems and technologies that are supposed to be safer; however, I am reserving my right to see how they perform over time, rather than jumping on any bandwagons.

I also have concerns about the potential genetic mutations that can occur from injecting what are called retroviruses of this class, and long term immune suppression and other diseases and/or cancers occurring in vaccinated animals. That is why it has been so difficult to develop a safe and effective human AIDS vaccine as well. Therefore for those guardians who choose to vaccinate their outdoor cats for feline leukemia virus, I would stress that they learn more about the issues/concerns I raise here, rather than blindly following every year vaccination programs for their cats.

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  1. Dr. Dym. I appreciate your conservative approach to vaccinations. You mentioned the use of immune stimulants including Vetri-DMG liquid and VitaChews for Cats, and links, but you were not specific as to your source for Transfer Factor. The only source I know for Transfer Factor is from a company I am affilated with and purchase from .. .4Life Research. They hold original patents on a few advanced formulations that will boost immune system activity by up to 437%. They also have specific formulations for pets. Can you comment please?

  2. I have 2 orphan kittens that are 8 weeks old SundayJan12. I want to buy vaccines for them,Distemper,Leukemia,?? I want 2 Rabies shots for when they’re a little older.I live in Maryland!
    Can you Please help me. Single dose with syringe needle if you carry these!Thank you.There might be one othe5r Vaccine with that 1st set but I can’t remember too long since I ‘ve had kitten. Do you follow this up for a total of 3 doses 2-3 weeks apart?? How much do they cost?Thank you for your help!

  3. Thank you soooo much. We’re very secluded back on 35 acres..Until warm weather they are indoor kitties 24/7!! I can’t remember vaccinating our kitten with all that! And I believe growing up I was told ‘cats’ don’t get rabies! If I do keep them indoors they should be fine. We’re 1/2 mile back country road,no other cats around!! We have 2- dogs,Boxer & Great Dane live inside but do go out with me!1-female already certificate to spay 2nd is male have to line up for him to be neutered when they’re 6 months if my memory serves me right!! Thank you so much for your help and good to know answers. Sincerely,Lynn Bourne

  4. Dr. Michael Dym, VMD veterinarianJanuary 13, 2014 at 12:29 am

    I am a minimalist when it comes to vaccinations. I only vaccinate for panleukopenia/rhinotracheitis virus two doses 4 weeks apart at age 10 and 14 weeks of age, should give you many years, if not life time immunity. Rabies is required by state law in most cases and should be given separately 4 weeks after last panleuk shot in my opinion. I am not fan of feline leukemia vaccination as I dont think it works or is necessary and has chronic side effects in my experience

  5. Dr. Michael Dym, VMD veterinarianJanuary 13, 2014 at 12:29 am

    Answered question already

  6. I am currently caring for 4 kittens, 3 months of age, who have all tested “slightly positive” on the FeLV test. At their first visit to the vet (at about 6 weeks of age) the vet gave them the routine first vaccinations…now I am reading about “minimal vaccinations” for kittens. We are giving them a high quality diet along with Feline Transfer Factor hoping maybe they can clear the virus. My question is…the vet is recommended another series of shots in about 2 weeks along with testing again for FeLV. I am hesitant to give them more vaccinations…should we hold off? They are kept completely indoors and not in contact with any other animals.
    Thanks for any advice.

  7. Dr. Michael Dym, VMD veterinarianJuly 25, 2014 at 9:08 pm

    Hi Roberta. I wholeheartedly agree with your concern about offering more vaccinations, especially at a time when the kittens’ immune systems are maturing and/or trying to fight off potential feline leukemia virus exposure. I love the transfer factor, although I prefer the transfer factor plus human version, even in cats. I would also considering consulting with a veterinary homeopath. To learn more about homeopathy, see the information on my website, as well as http://www.drpitcairn.com Many homeopaths like myself do offer phone consultations http://www.doctordym.com

  8. My 4 yr. old cat has feline leukemia . I heard colostrum would be great to give her. I don’t know how much or how many times a day I should give it. Can you help please! Running out of time!.

  9. Dr. Michael Dym, VMD veterinarianAugust 10, 2014 at 2:57 pm

    HI Bernadine. See my friend and colleague’s website Stephen Blake, DVM, who has excellent information on colostrum, dosing, etc as well as other supportive treatments for feline leukemia virus. http://www.thepetwhisperer.com Hope this helps.

  10. Thank you for your views on vaccinations. It’s always great to get another perspective. Have you heard about LTCI (Lymphocyte T-Cell Immunomodulator) as a treatment for cats with FIV or FeLV? http://tcyte.com

  11. Dr. Michael Dym, VMD veterinarianSeptember 12, 2014 at 4:23 pm

    I am not familiar with this product.

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