Austin Pets Alive! is a large shelter in Austin Texas that adopts out approximately 400 FeLV foster cats a year. The shelter receives hundreds of FeLV+ cats from other shelters across the country and confirms the infection upon arrival with a SNAP FeLV test. However, there is much controversy about the best testing strategy and type of blood sample to use for FeLV diagnosis. For animal shelters, test accuracy, short turn-around time, and cost are important features.
To answer the question, “What is the best test for FeLV?” the Shelter Medicine Program at the University of Florida collaborated with Austin Pets Alive! and IDEXX Laboratories in a study funded by Maddie’s Fund and the EveryCat Foundation to run all of the most popular tests side-by-side every month for 6 months. A total of 127 FeLV+ cats were enrolled in the study. They lived in foster homes for the first 6 months and were then adopted into their lifelong homes (often by their fosters) to continue their long-term follow-up.
Phase I: Search for the best FeLV test
Once a month for 6 months a blood sample was collected for an extensive panel of FeLV diagnostic tests:
- SNAP ELISA using whole blood, plasma, and serum: FeLV soluble antigen
- Quantitative Petchek plate ELISA with plasma and serum: FeLV soluble antigen
- Immunofluorescent antibody (IFA): cell-associated FeLV antigen
- Quantitative PCR: FeLV proviral DNA
Phase 2: The FeLV Lifetime Study
We’ll continue to follow the outcomes of all of the cats enrolled in the study to learn more about their longevity and how it’s related to the results from the test panels. We are now in the 7th year of tracking the cats, the longest follow-up ever performed in a large cohort of FeLV+ cats.
An important discovery: FeLV virus level at the time of diagnosis predicts long-term survival
After sifting through the results of the FeLV testing panels, an important connection was made. Cats with a high level of FeLV provirus in their blood at the time of diagnosis had a high risk for early death. We termed these High Positive cats. In contrast, cats that were infected, but had a low level of provirus and cats that were positive for p27 antigen but had undetectable provirus were likely to have a long survival similar to uninfected cats. We termed these Low Positive cats. This finding led to a new testing protocol used by the Shelter Medicine Program at the University of Florida starting with point-of-care screening tests for p27 soluble antigen and adding follow-up testing with laboratory p27 tests in combination with quantitative PCR when indicated.
