challenge. First, because we knew that the vaccine is not fully effective, being unable to test for infection was a significant drawback. Second, vaccinated cats who ended up in shelters or rehomed could be wrongly suspected
of having FIV infection when, in fact, they were merely vaccinated. Given these challenges associated with vaccination, FIV vaccination fell out of favor. An FIV vaccine has not been commercially available in the United States since 2016.
DIAGNOSIS OF FELV/FIV: A SUMMARY
antigen; this test will often be positive within six weeks of exposure. When screening for FIV, in contrast, the ELISA is an antibody test; it may take up to 60 days post-infection for antibody levels to be detectable on an ELISA. These two tests also differ in the appropriate response to a positive ELISA. For both FeLV and FIV, a positive result requires a confirmatory test. However, a confirmed positive FeLV result also requires repeated testing to determine whether the infection is regressive or progressive.
Veterinary practices perform countless FeLV/FIV ELISA tests every day, but it is relatively uncommon to obtain a positive result for FeLV or FIV. Therefore, it is important to review the differences in testing between these two viruses and be aware of how to proceed when a positive result is encountered. While FeLV and FIV have similar indications for testing, they differ in their testing strategy. Initial screening for FeLV is typically performed using an ELISA test that detects FeLV
FeLV
FIV
Type of Test
Antigen
Antibody
Indications for testing • Illness
• Illness • Potential exposure • Unknown history
• Potential exposure • Unknown history
Time from infection to positive test result What to do with a positive ELISA test
6 weeks
60 days
• Confirm the positive result (PCR). • In kittens <4 months of age that test positive and repeat test after 4 months of age to rule out maternal antibodies as source of a false positive.
• Confirm the positive result (another brand of ELISA test, saliva RT-PCR test, or a blood provirus PCR test). • If positive result is confirmed, determine whether infection is progressive or regressive (retest at 6 wks, +/- 12 wks).
CONSIDERATIONS FOR SHELTER/RESCUE CATS
virus, which is considered less transmissible between housemates, posed less of a threat to adoption; 49% said they would place an FIV-positive cat in a multi-cat home. However, these are not the only possible outcomes. In this study, 43% of shelters routinely euthanized cats testing positive for FeLV and 26% routinely euthanized FIV-positive cats; euthanasia was more common in municipal shelters, high-volume shelters, and rural areas. The AAFP recommends that FeLV- and FIV-positive cats be afforded the same adoption opportunities as other cats (Little et al., 2020). These cats are suitable candidates for adoption, as long as adopters receive appropriate education. Additionally, these cats can attend adoption events and be housed in shelter adoption rooms, as long as they can be housed individually (Little et al., 2020). Expanding the adoption of FeLV- and FIV-positive cats can support shelters in their mission to successfully rehome pets and decrease euthanasia rates. When cats do become infected with one of these retroviruses, practitioners should remain mindful of the fact that many cats exposed to FeLV will successfully suppress the infection; less than half of infected cats will develop progressive FeLV infection. This is in direct contrast to FIV, where all cats that become infected with the virus will eventually develop signs of infection. Although FeLV and FIV are both initially diagnosed using a combined ELISA SNAP test, a positive result for either test should be confirmed through further testing. Because of the possibility of regressive infection, even
In the shelter setting, approximately 5% of cats will test positive for FeLV or FIV (Dezubiria et al., 2022). This can present a challenge for shelter veterinarians, who must decide how to address these cats while using limited resources efficiently. According to a survey of 139 animal shelters in Florida, 83% of shelters conduct some form of FeLV/FIV point-of- care screening in cats (Dezubiria et al., 2022). However, these shelters do not necessarily test every cat that comes through their doors. Of those shelters offering testing, just 49% test all cats for FeLV and 45% test all cats for FIV. Testing rates are higher in private rescue groups than in municipal animal shelters. Shelters differed in how they handled cats that tested positive for FeLV or FIV. Most shelters said they would only adopt an FeLV-positive cat to a home with no other cats; however, 10% said they would place an FeLV-positive cat in a home with other cats. Feline immunodeficiency Conclusion Feline leukemia virus and feline immunodeficiency virus can both have significant impacts on the health of feline patients. Although there are many similarities between the two viruses, including their impacts on the immune system and ability to produce neoplasia, it is important for veterinary practitioners to remain mindful of the differences between the viruses. When thinking of epidemiology, it may be helpful to remember that FeLV is typically a disease of “friendly” cats that are in close social contact, whereas FIV is a greater concern in cats that fight and receive bite wounds.
Page 67
Book Code: VFL1526
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