June 30, 2018

Audience: Executive Leadership, Shelter/Rescue Staff & Volunteers, Veterinary Team

Organization: University of Florida
Investigator(s): Julie Levy
Grant Amount: $160,000
Project Type: Basic Research
Project Status: Research Complete

Project Summary

The University of Florida evaluated whether cats at Austin Pets Alive! who tested positive for Feline Leukemia Virus (FeLV) at intake would remain positive upon retesting, by 4 different methods, at one month intervals for 6 months. The study found that a single test, or a test given at a single point in time, may not be sufficient to determine if a cat has FeLV or not, and that commonly used confirmatory tests may not be definitive. Practical follow-up tests are needed to help determine disease status with the understanding that FeLV disease states may be better represented as a continuum instead of discrete states.

Objective(s)

To find out how many cats will test negative within six months of their initial FeLV diagnosis

Methods

A total of 130 FeLV positive (96 juveniles and adults, 34 under 2 months of age) and 130 negative cats were enrolled based on test results at intake. Cats were screened on intake to Austin Pets Alive! using anticoagulated whole blood. Collection of monthly whole blood, plasma and serum samples began once cats weighed at least two pounds. Samples were tested by SNAP Combo, a quantitative p27 antigen ELISA, a semi-quantitative real-time PCR for proviral DNA, and FeLV IFA. Cats were classified as "progressively infected" if they consistently tested positive across all 4 testing methods during the study period.

Results

• 50% (17) of the cats under 2 months of age who tested positive at intake were deemed "progressively infected" at the end of the 6-month study, as compared to 78% (75) of the cats over 2 months of age.
• 50% (17) of cats under 2 months of age and 22% (21) of juvenile/adult cats were deemed "regressive/discordant;" 5% (6) cats "recovered" (meaning that all tests were negative by 6 months).
• Two antigen-negative cats (1.5%) had evidence of proviral DNA by PCR.

Conclusions

A test taken at a single point in time, or even a single test, may not be sufficient to determine a cat's FeLV status. As shown, a notable portion of cats may test negative or regressive upon retesting. These cats typically do not develop FeLV-associated diseases and live a normal lifespan. Lack of awareness, understanding and adequate guidance on this issue can often result in the euthanasia based upon a single positive screening test. More research is required to: develop guidelines for shelter managers and private practice veterinarians; and continue to evaluate the costs and value of FeLV testing in shelters. Practical follow-up tests are needed to help determine disease status with the understanding that FeLV disease states may be better represented as a continuum instead of discrete states.