////////////////////////////////////////// Shelter Medicine

To Test or Not to Test Confronting feline leukemia and feline immunodeficiency virus

By Lila Miller, D.V.M.

Lila Miller is the ASPCA’s vice Just because a cat tests positive for FIV or FeLV doesn’t mean he has a clinical disease; it only points to president of veterinary outreach possible infection. Tests are not always accurate, and no healthy cat should be euthanized based on the results of only one. Dan Brandenburg/istockphoto.com and veterinary adviser.

eline leukemia (FeLV) and feline FIV-infected cats can live for many years direct oro-nasal contact between cats, mu- immunodeficiency (FIV) viruses after diagnosis. tual grooming, and shared contaminated are always near the top of the Deciding whether to use your shel- water bowls and litter boxes. It can also be list when shelter workers discuss ter’s scarce resources to test for these transmitted across the placenta, through diseases of concern. Despite the diseases can be difficult. In order to make contaminated needles, via fomites (hands Fmore devastating effect that upper respi- the appropriate choice, shelter managers or inanimate objects that act as virus-bear- ratory infections, ringworm, and feline and veterinarians should review current ing surfaces), by nonsterile surgical instru- distemper can have on the shelter’s feline information about these two retroviruses, ments or contaminated blood transfusion. population, FeLV and FIV always seem to including the transmission, prevention Young kittens and cats less than 1 year old generate greater discussion, due to the and control, diagnostic testing protocols, are the most susceptible; healthy young fact that both diseases cause life-threat- and methods of caring for infected or test- adults are less infectable. FeLV does not ening problems, and diagnostic testing is positive animals in the shelter. live long outside the body and is readily in- required to detect infection. activated by most disinfectants. Luckily, shelter outbreaks of FeLV or Feline Leukemia Virus: Many cats who are in the early stages FIV are not common because the viruses A Common Killer of infection show no obvious clinical signs. are not highly transmissible, cause chronic This complicated disease was first re- Often, symptoms of feline leukemia infec- infection rather than acute disease, do ported in 1964, and has been one of the tion can be vague and nonspecific, and not survive outside the body long-term, most widely researched infectious feline can include vomiting, loss of appetite and and are easily killed by disinfection. And diseases. FeLV occurs worldwide, and al- weight, lethargy, and anemia. Since FeLV in shelters increasingly able to find homes though prevalence varies according to geo- can be a primary cause of leukemia or for animals with health issues, positive graphic region, it remains one of the more lymphoma—both cancers that can affect results on an FeLV and FIV test may no commonly diagnosed causes of disease and multiple organs—as the infection pro- longer constitute automatic cause to eu- death in domestic cats. The virus is shed in gresses, symptoms that correlate with the thanize otherwise healthy individuals. many bodily fluids, including urine, saliva, affected organ system may be observed. Studies have shown that with good pre- milk, tears, and blood, and in feces. It is For example, if the liver is affected, jaun- ventative health care, some FeLV- and most commonly transmitted by prolonged dice and liver enlargement might be seen;

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Test brands vary in the case of brain lesions, seizures, but prevalence varies geographically. blindness, and behavior changes may Fortunately for shelters, the virus does widely in their occur. FeLV-infected cats may be suscep- not survive longterm outside the body sensitivity and tible to other infections because infec- and is easily killed by routine disinfection. specificity, and tion suppresses the immune system; they In July of 2002, the first licensed vac- commonly succumb to other diseases. cine against FIV was introduced in the the shelter should The first FeLV vaccine became avail- United States. This is a killed product. It always bear in mind able almost 20 years ago, and there are is not 100 percent effective in prevent- that no test is accurate several vaccine products on the market ing infection but may have use for cats today that help protect cats from infec- in high-risk settings like shelters. Once 100 percent of the tion. Of the vaccines currently available, administered, a cat will test positive on time under all all are inactivated (killed) products that an antibody test, so determining the FIV conditions. are neither capable of causing disease nor status prior to vaccination and docu- replicating, and they do not interfere with menting the vaccination status of cats is It is always diagnostic testing. The vaccines are not extremely important. recommended to 100 percent effective in preventing infec- closely follow the tion, but they can significantly help cats at Is it Time to Test? risk. Individual cats should be tested prior When making a decision about testing for manufacturer’s to vaccinating because the ability to iden- any disease, there are several key things instructions for tify and isolate infected cats is considered to consider. If testing is going to be per- test performance the most effective means of protecting formed in a shelter, achieving an accurate a population of cats against exposure. diagnosis is especially important, since and storage. Vaccination will not reverse the FeLV- test results often result in life-and-death positive status, nor will it prevent the de- decisions. The sensitivity and specificity velopment or transmission of disease. of the test should be understood. The cost of testing in relation to the information FIV: The Feline AIDS gained should be evaluated. Finally, what FIV is responsible for a fatal disease syn- will be done with the resulting informa- drome in cats that is similar to HIV infec- tion? Will it be used to make a definitive tion in humans. It is often referred to as diagnosis—even though no single test is “feline AIDS,” and has not been found to 100 percent perfect—or will confirmatory be contagious to humans or other animals. testing be performed? Will it be used to Because the virus affects the immune sys- protect other animals’ health? Will it be tem, viruses, bacteria, protozoa, and other used to determine adoptability? disease organisms can cause severe ill- In the case of both viruses, there are ness in FIV-positive cats. This is obviously many brands and types of FeLV tests a big concern for shelters, where the risk available. One commonly used by shel- factors for exposure to disease increase ters is the ELISA (enzyme linked im- Since vaccination or maternal antibodies will not interfere with the test, cats of any age can be dramatically. As with HIV, cats can test munosorbent assay) test. This test is tested for feline leukemia. Monique Rodriguez/ FIV-positive years before showing any typically used for detecting FeLV anti- istockphoto.com outward signs of clinical illness. gen and FIV antibody. Test brands vary When symptoms do occur, they can widely in their sensitivity and specific- be varied and vague, ranging from fever ity, and the shelter should always bear in and lethargy to enlarged lymph nodes mind that no test is accurate 100 percent and cancer. FIV is transmitted primar- of the time under all conditions. It is al- ily through bite wounds and is therefore ways recommended to closely follow the much more common among outdoor, manufacturer’s instructions for test per- intact male cats who are most likely to formance and storage. In most circum- fight. For this reason, FIV may be found stances, testing with serum or plasma more commonly in adult males than kit- yields more reliable results than testing tens or adolescents. On rare occasions it with whole blood, saliva, or tears. may also be transmitted from mothers to When performing tests, the preva- kittens during birth and through nursing. lence of the diseases in the local commu- Like FeLV, the disease is found worldwide, nity must be considered in relation to the

56 Animal Sheltering september/october 2008 ANIMALSHELTERING.ORG ////////////////////////////////////////////// test results. Prevalence of both FIV and FeLV has been found to be as low as 1 to 3 percent in healthy, free-roaming cats in the United States. In cats with health is- sues (bite wounds and abscesses), the prevalence increases. When a negative test result is obtained in an otherwise healthy cat using a test with good sensi- tivity and specificity, odds are good that the result is correct. When a positive test result is obtained from a seemingly healthy cat, it can indicate either that a cat is infected, or the test result may be a false positive. Shelters must decide what to do if they get a positive result in an asymptom- atic cat, understanding that it could be a false positive. There are confirmatory test methods for both FeLV and FIV rec- ommended by the American Association of Feline Practitioners for every positive ELISA test, but not every shelter will be able to hold cats while awaiting confirma- tory results. Contradictory results may still be found, and the cost of confirma- tory testing may be prohibitive.

Shelters and FeLV Testing n Cats with clinical signs of illness who test positive do not necessarily have clinical illness related to FeLV—it could be something else! n To confirm positive test results: 1) Another brand of test can be used ini- tially to double check the first result; 2) an immunofluorescent antibody test (IFA) can be performed; 3) other tests, such as PCR, are available and can be utilized. n Confirmed positive test results indicate infection but do not equate with clinical disease. n Vaccination and maternal antibodies do not interfere with the test, so it can be performed on cats at any age (although newborns may not test positive for sev- eral weeks). n Queens and each member of a litter should be individually tested. n After a potential leukemia exposure, it can take a variable amount of time for testing to reveal a positive result. A minimum of 28 days is recommended before testing, and if an exposed cat

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populations, the fact that neither virus is highly transmissible, the inability of the viruses to live outside the host very long, and the inability of most programs to per- form tests that confirm positive results on healthy animals. If a decision is made to test and house FeLV- and FIV-positive cats in the shelter, several precautions should be observed. n These cats should be isolated from un- infected cats and housed individually or in stable colonies in which fighting is unlikely to occur. n FIV-positive cats should not be housed with FeLV-positive cats. n Extra sanitation measures should be observed, such as more frequent hand washing and disinfection, with staff wearing disposable aprons and utiliz- Deciding whether to use your shelter’s limited resources on testing for FIV and FeLV can be difficult. It’s ing disposable rags, towels, etc. when important to consider how the test results will be used—whether the purpose is making a definitive diag- nosis, determining adoptability, or protecting other animals’ health. ObservePhoto/istockphoto.com cleaning areas housing these animals. Although the diseases are short-lived tests negative, serial retesting at 30-day to double check the first result; 2) a outside the animal’s body, fomite trans- intervals is recommended. Western Blot test is considered confir- mission is still possible, and care must n Discrepancies between ELISA and IFA matory if positive. also be taken to not expose these cats test results may reflect differences in the to infectious disease from the unin- stage of disease. Conflicting test results Management in shelters fected cats. should be discussed with a veterinarian FeLV/FIV screening tests should be a pri- n Stress should be minimized. and the testing laboratory before a final ority in shelters that: n These animals should be vaccinated with decision is made about a cat’s health. n group house cats; the FVRCP vaccine, dewormed, treated n treat infectious disease; for external parasites, and neutered. The lowdown on FIV testing n house cats long term, especially cruelty n Cats who are very debilitated may and other legal cases; Advice for Adopters be unable to produce any antibodies, n neuter prior to adoption, as opposed to Whether a shelter performs the initial which would yield a negative test result at adoption. Given that FeLV/FIV posi- tests or not, adopters should be advised although the cat has the disease. tive cats may be more difficult to re- about these diseases and informed that n Infected mother cats can pass their an- home, shelters may want to consider establishing and tracking the FeLV/FIV tibodies to their kittens, so kittens who whether to invest in the surgery, and status of their new cat is an important are tested before 6 months of age may should keep in mind that the occasional part of preventive health care. Due to the actually test falsely positive until their post-operative infection may be more incubation period of these two retrovi- mother’s antibodies are eliminated from difficult to treat in an FeLV-positive ruses, repeating a second FelV/FIV test their bodies at around that age. So un- animal. 60 to 90 days after the cat has entered a like the feline leukemia test that can be Shelters that are involved in trap- stable environment is a good idea. performed at any age, FIV testing that neuter-return programs for management If adopting a retrovirus-positive cat, is performed before 6 months of age of feral cats often face the dilemma of adopters should be fully informed about should be repeated at 60-day intervals whether or not to perform FeLV and FIV the disease in question and the risks the if a positive result is obtained. tests. Many programs, such as Operation infection may pose to uninfected cats al- n It may take eight to 12 weeks after an Catnip (operated by the University of ready in the household. Adopters must FIV exposure to produce detectable lev- Florida) and the ASPCA in New York be advised that positive cats should els of antibodies, so it would be prudent City, have chosen not to test but to utilize be confined indoors, both to prevent to retest exposed cats 60 to 90 days the money saved to perform more spay/ spreading the disease to other cats and after the exposure. neuter surgeries. The decision not to test to keep themselves from being exposed n To confirm positive results: 1) Another is based on a variety of factors: the low to other animals that may be carrying brand of test can be used initially prevalence of infection in free-roaming infectious disease. They must be fed a

58 Animal Sheltering september/october 2008 ANIMALSHELTERING.ORG ////////////////////////////////////////////// nutritionally complete feline diet, and hunting, raw foods, and unpasteurized milk should be avoided. Routine, semi-annual visits to the veterinarian should be scheduled, with particular attention paid to oral health. Any illnesses or abnormalities should be reported to the veterinarian promptly; re- member that these animals are likely to be immune-compromised, and response to therapy may take longer. The adopter may also be advised to weigh the cat reg- ularly since weight loss may be one of the first signs of a problem.

In the Shelter’s Hands The American Association of Feline Practitioners (AAFP) recommends that the FeLV and FIV status of every cat should be known. Its guidelines also state that no healthy cat should be eu- thanized based on the results of one single test. In an ideal world, all shelter cats would be routinely screened in ac- cordance with these guidelines, and their disposition based upon repeated confir- matory testing of healthy animals with suspicious results. However, I believe the individual shelter should decide whether deter- mining the status of every cat prior to adoption is the best use of its limited resources. A positive test only indicates that the cat may be infected with the virus, not that he or she has clinical dis- ease, and the tests are not 100 percent accurate all of the time. Many shelters cannot afford to hold otherwise healthy animals for retesting, and any positive result, regardless of the health status of the animal, can result in euthanasia. In shelters that euthanize animals for space and disease, it is a questionable use of resources to test all adoptable cats, but then perhaps eu- thanize the animal a few days later just because a new home cannot be found right away. Ultimately, since resources are limited, shelters must decide which animals to test, when to test, how test results will be used, and what the risks and the benefits in testing a population of healthy cats with low prevalence of disease might be. AS

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