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The James A. Hueholt Memorial Foundation for Animals


Feral Cat Health: FeLV/FIV Testing
by Beth Mersten, Best Friends Animal Society & Anita Frullani, Castaway Critters

*Note: While this article pertains mainly to feral cats, this information also is useful for friendly stray and pet cats.


Whether you are a colony caretaker or a program director of a feral cat spay/neuter program, there are some issues regarding the testing of retroviruses such as Feline Leukemia (FeLV) and Feline Immunodeficiency Virus (FIV) to consider.


There are many sources of information regarding feral cats and testing these cats for FeLV/FIV. Here, we give you scientific data based upon published research performed by veterinarians and scientists; information from the American Association of Feline Practitioners, a chapter of the American Veterinary Medical Association; as well as recommendations from some of the largest and most well-respected feral cat organizations in the United States, including Alley Cat Allies, a leader in the TNR field.

If a cat initially tests positive for FIV or FeLV, it does NOT mean the cat is positive. The words "test positive" are specifically used because "we are not talking about cats who have the disease or even are positive, but cats who test positive and that's a very important distinction", says Nathan Winograd, former Director of the San Francisco SPCA and current Director of the Tompkins County Humane Society.


Nathan Winograd states "the San Francisco SPCA realized that the incidence rate of positive cats is the same for feral cats as it is for the pet cat population. Twenty percent of cats who test positive will be false positive cats ... higher with kittens. Besides wasted funds and false positives, in the end only about 10% of cats who are infected with FIV actually come down with the disease. Ninety percent -- 9 out of 10 infected cats -- will lead completely normal lives."


"Essential to the decision-making process is an understanding of the nature of both viruses and the limitations of the tests used to detect them," cautions Alley Cat Allies. The tests are not always accurate, reports the American Association of Feline Practitioners. For FIV, the testing method used most widely is the ELISA (Enzyme Linked Immunoabsorbent Assay) test, which detects whether FIV antibodies are present in the blood -- not whether the virus itself is present, explains Neighborhood Cats. "As a result, the test is completely unreliable for cats under six months of age who may have received FIV antibodies from their nursing mother, but may never have been exposed to the actual virus. For adult cats, because of the recent introduction of the FIV vaccine, there is now the possibility a positive test result means a cat has been vaccinated, not infected. Also, a positive result may only indicate recent exposure, not infection."

The most commonly used ELISA is the IDEXX SNAP test. Neighborhood Cats continues, "The ELISA is also used for FeLV. The test is extremely sensitive and is prone to false positives from improper handling. In addition, a cat in the early stages of FeLV infection can still fight it off."


The AAFP guidelines state that a cat testing positive after a single test must be re-tested using a second method of testing after a specific period of time. It is usually impractical if not impossible to hold a feral cat for the period of time necessary for re-testing purposes (AAFP/Griffin).


TNR experts Alley Cat Allies recommend that "before making a decision on testing, it is important to assess the cats you are planning to trap and formulate a management plan first. Are the cats truly feral or are the cats strays? Will the cats go back to the colony or be homed? Clearly, tamable kitten and strays should be tested before being placed in foster or adoptive homes so they can be cared for properly. But what about untamable adults who will be returned to the colony site?"


Studies performed by Dr. Julie Levy, DVM, founder of Operation Catnip-Gainesville-FL, and other veterinarians and scientists published in the Journal of the American Veterinary Medical Association have shown that "there is no greater incident of disease in feral cats than there is in tame, owned free-roaming cats." The average rate of infection is 3 to 6% of both pet cats and feral/stray cats, reports Dr. Brenda Griffin, Veterinarian and Professor at Scott-Ritchey Research Center, College of Veterinary Medicine, Auburn University.


Studies show that using our scarce economic resources to sterilize more cats than otherwise would be sterilized given the cost of testing, actually works to more quickly reduce the number of FeLV positive cats considering that our area has a euthanasia rate of over 50% for cats (AZCats, AAFP, CPAA). In addition, removing a cat who has initially tested positive from a colony does not "eliminate the risk of infection to other cats, who have likely already been exposed to the virus, anyway." (Neighborhood Cats). In addition, exposure does not mean infection (AzCATS).

Neighborhood Cats says the "primary cause of infection relates more to proper colony management than to a particular positive cat or cats. In our experience, colonies with lots of sick cats are ones that are poorly managed - poor nutrition, inadequate shelter and/or unneutered animals. These conditions lead to weakened immune systems and susceptibility to disease. Indeed, some veterinarians believe it is rare for a healthy adult cat to ever catch FeLV. The best way to prevent the spread of disease is thus not by killing individual cats, but by improving the quality of food, making sure the cats have warm, dry shelter in winter and getting them neutered."


Alley Cat Allies says that "despite their being concern over viruses, there is no feline disease that kills more cats than overpopulation." Viruses can be reduced by simply by implementing a high volume sterilization program. In fact, Alley Cat Allies, AzCats and Operation Catnip all state that sterilization reduces or eliminates the behaviors which spread disease---roaming, fighting, mating, and the production of kittens.


Feral cats who are cared for by a caretaker are sterilized, and live in managed colonies are very healthy, studies show. It is unaltered cats, regardless of whether they are from feral colonies or private homes, that wander, fight, reproduce, and have the potential to spread disease. Sterilization reduces or eliminates the behaviors which spread disease (AZCats/Operation Catnip).


Some caretakers believe that placing cats that initially test positive for either FIV, FeLV or both, together is a viable option. It is important to keep in mind that the cats may be in the process of fighting off a virus. If one makes the decision to test, it is important to follow the AAFP testing guidelines and re-test.

Even if a cat happens to be FIV+, Neighborhood Cats founder Bryan Kortis says "An FIV cat especially should not be around FeLVs, because an FIV cat could lead a very long life around other, non-FIV cats. But putting them around FeLV positives means they'll catch that virus too, being immune-compromised, and die early."


Removing a cat that tests positive will not necessarily prevent the spread of infection within the colony since the colony's exposure to the virus would already have occurred. Kortis and AzCATS suggest these positive cats have a much better chance when left in their colonies and monitored for if and when the day comes that they reach a terminal stage (AzCats/Neighborhood Cats).


FIV is transmitted primarily through deep, penetrating bite wounds made by male unneutered cats, who roam and fight other unneutered males over territory and females. It is unlikely for a mother cat to infect her kittens with FIV (Alley Cat Allies). Nathan Winograd explains that because the primary modes of transmission of FIV are bites, neutering will go a long way to prevent the spread of FIV because altering affects both:  


"reducing or eliminating fighting as well as roaming and mating." 


Veterinarian and researcher of feral cat issues, Dr. Julie Levy, states FeLV is transmitted primarily from mother to kittens. It also is transmitted via saliva by mutual grooming and sharing food dishes. Therefore, spaying these cats reduces the primary transfer of the virus by eliminating the capacity for reproduction.

When talking with Alley Cat Allies, Dr. Levy of Operation Catnip posed two provocative questions: "Will testing cats reduce the number sterilized?" and "Will returning sterilized infected cats reduce the spread of disease?"


Dr. Levy's scientific model below, excerpted from Alley Cat Allies "Overpopulation Kills More Cats Than Any Disease", is based on two assumptions. One being that the female cat produces 5.7 kittens per year that survive to adulthood; and two, 75% of an FeLV infected queen's kittens also become infected.


Effect of Test and Removal on FeLV prevalence

  Without Operation Catnip Operation Catnip, testing and euthanizing FeLV+ cats Operation Catnip, no testing
# cats sterilized 0 833 1500
# cats left intact 1500 667 0
# intact females (65% of population) 975 434 0
# cats tested and euthanized 0 58 0
# FeLV positive cats (7% of population) 105 (all intact) 47 (all intact) 105 (all altered)
# kittens born in one year (5.7 per female) 5,558 2,474 0
# FeLV positive kittens born 292 130 0
Total # FeLV Cats and kittens 397 177 105


As you can see, this model shows the "effectiveness of sterilizing a greater number of cats over testing and neutering or not doing anything at all" (Alley Cat Allies).


As a result of the scientific studies regarding testing and feral cat population control, numerous organizations operating large-scale feral cat spay/neuter clinics have changed their policies regarding the testing of FeLV and FIV. Among the many organizations which no longer test nor recommend testing are:

*Alley Cat Allies,
*Neighborhood Cats,
*Operation Catnip, Gainesville, FL, (Note: This group also has clinics operating in Richmond, VA and Raleigh, NC),,,;
*Feral Cat Coalition,
*Azcats (note Azcats has merged with Altered Tails),


Best Friends' Veterinarian, Dr. Richard Allen says "FIV is not limited to domestic (house) cats but can be found in the big cats as well, 84% of Seregenti lions harbor FIV and the virus has been identified in 25 species of cats around the globe, from cougars in Wyoming to snow leopards in the Himalayas. It appears that felines have gradually developed the ability to live with the FIV virus for long periods of time. FIV should not be a sentence or a stigma. It's time to end the fear and misinformation about this virus and to spread the truth about FIV." Dr. Allen also says it is possible to keep a FIV-infected cat in the same household (or colony) as a healthy cat with little risk of transmission as long as the cats tolerate each other and are not fighting.

In closing, Dr. Levy said "it is important to remember that we are in the midst of a crisis. Shelters all over the country are killing stray and feral cats at an alarming rate. Increasing the number of animals who are spayed and neutered is the single most effective way to help control the crisis and reduces the suffering of stray and feral cats" (Operation Catnip Interview).

Sources for this fact sheet:

*Central Pennsylvania Animal Alliance, 2003 Statistics
*FIV Ӣ Catching a bad Case of Rumors, Kristi Littrell,

*Brenda Griffin, DVM, Feral Cat Q & A for Veterinarians,
*Neighborhood Cats, Releasing FIV/FeLV Positive Cats,
*NMHP Forum, Best Friends Network Coordinator Beata Liebetruth,
*Should We Release Feral Cats Who Test Positive for FIV?, Nathan Winograd,
*To Test or Not to Test,
*AZ Cats (note: AZ Cats has merged with Altered Tails),
*American Association of Feline Practitioners Testing Guidelines, 
*Building the Body of Evidence that TNR Works, Julie Levy, DVM
*American Feline Association of Feline Practitioner's Position Statement,
*Interview with Operation Catnip's Dr. Julie Levy,
*Overpopulation Kills More Cats than Any Disease,

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