////////////////////////////////////////// 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; GET READY TO CELEBRATE YOUR SHELTER! ANIMALSHELTERING.ORG/SHELTERSROCK 55 SheLter Medicine ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 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.