Just Say YES: Why FeLV Vaccines are Important to your Kitten’s Health

A few weeks ago, I wrote about FIV vaccines and why you should never, EVER give them to your cat. But let’s get one thing clear – I love vaccines. Vaccines are awesome. They’re an integral part of public heath (including pet health!), and your cats need them. The FIV vaccine is a special case in which the negative effects of vaccination outweigh the potential benefits.

With that being said, I want to talk about another non-core vaccine; one that you should ABSOLUTELY get for your kitten: the Feline Leukemia vaccine. (*Note: If you were thinking that FIV and FeLV are the same thing or you’re confused about the difference, read our blog post about the two diseases.)

Feline Leukemia is a potentially deadly disease that affects cats. Kittens are the most susceptible to becoming infected, and so they are the ones for whom the vaccine is most important. The American Association of Feline Practitioners (AAFP) recommends that all kittens be vaccinated for FeLV, although it is not considered a “core” vaccine for all cats.

It is most important if your cat is allowed outdoors. Although the prevalence of FeLV has declined (thanks to testing/isolation and vaccination programs), FeLV is still present throughout the United States, and your cat is at risk any time they go outside and have contact with another cat.

My kitten will be indoor-only, so why should I bother?

That’s fantastic! All cats should be indoor-only. But sometimes things happen, and your indoor kitten may slip outside for a jaunt around the neighborhood, where he could be exposed to various diseases including FeLV. He could get lost, he could get in a fight, and before you know it, you have a cat that is FeLV positive.

Why does Calvin’s Paws vaccinate all incoming cats for FeLV?

In the spring of 2015, the Calvin’s Paws Board of Directors made the decision to make FeLV vaccinations a part of the routine care that all new cats receive. We chose to do this for a number of reasons:

  1. Vaccination is a key part of any effort to eradicate any disease. Imagine if no one had to worry about FeLV anymore! That is the ultimate goal.
  2. The AAFP recommends the vaccination of all kittens, as well as adult cats that are kept in group-housing situations with other unrelated cats (as is often the case in foster homes).
  3. While we require our adopters to keep our cats indoor-only, the reality of the situation is that not everyone will comply. By vaccinating our cats, we are ensuring that they have minimal risk of developing the disease should they ever be exposed.

But all of your cats are tested for FeLV and FIV before they integrate with other animals in the program – so what’s the point of vaccinating if everyone is negative?

This is where things get interesting. FeLV is a sneaky disease, and in my experience, no case is “typical.” Recent research has shown that around 10% of cats that test negative on the standard in-house tests for FeLV actually do have the virus – it’s just extremely well-contained and suppressed by their immune system. FeLV is a retrovirus, and its modus operandi is to integrate into the DNA of its host. Once this happens, the immune system can’t get rid of it, even if it clears all of the active virus from its system. These cats are not shedding the virus and so are not contagious, and it’s unlikely that they’ll develop any FeLV-associated diseases. This is called a regressive infection. However, there’s a chance that if the cat later becomes immunosuppressed that the FeLV virus could become active again, and the cat would suddenly start testing positive and potentially develop FeLV-related diseases. As of now, it’s unclear how often this happens, or how significant it is. Because these cats test negative on the in-house tests that vets and rescues routinely use, there is no way for us to know if a cat has a regressive infection or if they are truly completely negative. Therefore, since many of our cats live in foster homes with other cats, the safest course of action is to vaccinate all of our cats. That way, if anyone later develops an active FeLV infection, the others in the household are protected.

Why doesn’t everyone already vaccinate their cats for FeLV?

One reason is that it’s not considered a “core” vaccine, so not all vets routinely recommend it – it just depends on the vet and the cat’s lifestyle.

FeLV vaccines are often criticized for not being 100% effective. However, some brands are better than others (Whole Inactivated vaccines are most effective, while recombinant vaccines are almost useless), and an adult, vaccinated cat has an extremely low risk of contracting FeLV upon exposure to the virus.

There has also been concern about vaccine-associated sarcomas developing after FeLV vaccination. A sarcoma is an extremely invasive type of cancer that can be difficult to treat. When FeLV vaccinations first started becoming common, vets noticed that the rate of sarcomas increased, and everyone panicked. Research has since shown that while there is a link between ALL vaccines (not just FeLV) and sarcomas, the incidence of a sarcoma developing at a vaccine site is roughly 1 in 10,000 cats. Considering that the prevalence of FeLV is roughly 2 in 100 cats (2.3% in a study done on the prevalence of FeLV in North America conducted in 2006), I’d rather take my chances with a sarcoma developing than my cat contracting FeLV, which can cause various cancers anyway. Besides, the rabies vaccine (which is required by law in North Carolina) has just as much risk as causing a vaccine sarcoma as the FeLV vaccine, but it has to be done. The benefit outweighs the risk.

The bottom line:

The FeLV vaccine is an important vaccine, especially for kittens. If we’re ever going to eradicate this deadly virus, vaccination is a key step. Be a part of the movement: vaccinate your kittens and keep all of your cats indoors.

References:

From the AAFP Retroviral Management Guidelines: (https://ca.idexx.com/pdf/en_ca/smallanimal/snap/triple/aafp-feline-retrovirus-management-guidelines.pdf)

  • FeLV Vaccinations: The decision to vaccinate an individual cat against FeLV should be based on the cat’s risk of exposure. Cats that live in a FeLV-negative, indoor environment are at minimal risk. FeLV vaccination is recommended for:
    • all kittens because the lifestyles of kittens frequently change after acquisition and they may subsequently become at risk for FeLV exposure
    • cats that go outdoors
    • cats that have direct contact with cats of unknown status or in high turnover situations such as foster homes or other group housing
    • cats that live with FeLV-positive cats

From the 2013 AAFP Vaccination Advisory Panel Report: (http://jfm.sagepub.com/content/15/9/785.full.pdf)

  • The Advisory Panel recommends that all cats under 1 year of age be vaccinated against FeLV and receive a booster vaccination 1 year later. After 1 year of age, the need for subsequent vaccination is determined by risk factors that the individual is exposed to.
  • Recommendations for Shelters – Feline leukemia (FeLV):
    • Administer a single dose of vaccine at the time of intake if group-housed. If group (rather than individual) housing for kittens is used, vaccinate as early as 8 weeks of age.
    • Revaccinate once, 3–4 weeks following administration of the initial vaccine.
    • Unlike group-housed cats, risk of FeLV transmission is very low for individually housed cats. FeLV vaccination is recommended for cats in long-term shelters or in group-housing of unrelated cats. Vaccination is not a substitute for testing and segregation of infected cats

Calvin’s Paws is a 501(c)(3) rescue. We work through a network of foster homes throughout the Triangle area to save homeless cats and dogs. We are a dedicated group of volunteers with common goals: rescuing animals (both positives and non-infected felines), finding the best fitting homes for each animal, and educating the public on animal health and responsible pet ownership.
www.calvinspaws.com

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Just Say YES: Why FeLV Vaccines are Important to your Kitten’s Health

5 thoughts on “Just Say YES: Why FeLV Vaccines are Important to your Kitten’s Health

  1. Shannon says:

    Our rescue does not administer this vaccine. It is adjuvanted (carries a greater risk of injection site sarcoma), only partially effective, and unnecessary in low risk populations. Many rescues in our area do administer it, but we choose not to. We do, however, follow strict retesting protocols for FIV and FeLV (which some rescues in our area do NOT do, unfortunately).

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    1. We (Calvin’s Paws) didn’t used to do it for those exact same reasons. However, we’ve seen a definite uptick in the number of cats testing positive over the last couple of years, and between that and AAFP recommendations, we decided to start doing it. We don’t have a central facility, and most of our cats are in foster homes where unrelated cats are co-mingled (adults with kittens, longtimers with new intakes, etc.). With cats coming in and out frequently in these foster homes, that counts as a higher risk population, especially since any cat can be harboring the virus and not test positive until they are stressed or immunocompromised. Most of the current vaccines are actually a lot more effective than the original ones developed, with about 85-98% efficacy (this is one of the more recent studies we looked at when deciding what kind of vaccine to use: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2822011/?tool=pubmed). Another factor in our decision was comparing the risk of vaccine sarcoma (about 1/10,000) to the risk of contracting FeLV (about 3/100) (http://jfm.sagepub.com/content/15/9/785.full.pdf – the discussion of vaccine sarcomas is on page 796). When faced with those numbers and our own personal experience, we decided that our best option was to start vaccinating for FeLV.

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    1. No – the test for FeLV looks for actual viral proteins (antigens), not antibodies. This is different from the FIV test, which looks for antibodies, which will be produced in response to a vaccine. A FIV vaccine will cause a cat to test positive for FIV, but a FeLV vaccine will not cause a cat to test positive for FeLV.

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