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Study findings clear the way for better protocol to screen cats for FeLV infection

Dr. Julie Levy

A new study from Dr. Julie Levy, the Fran Marino Professor of Shelter Medicine Education at the UF College of Veterinary Medicine, and her collaborators concludes that proviral DNA load and p27 antigen concentration are associated with survival in cats naturally infected with feline leukemia virus, or FeLV.

The study, “Feline Leukemia Virus p27 Antigen Concentration and Proviral DNA Load Are Associated with Survival in Naturally Infected Cats,” was published Feb. 15 in Viruses.

“Retroviruses continue to be important pathogens of domestic cats, and studies that further the understanding of disease outcomes are valuable for informing decisions in patients with these infections,” the authors write in the paper’s introduction. “Retroviruses are unique in that they contain the necessary enzymes to make a DNA copy of their RNA genome and integrate those genes into the chromosomes of an infected cell at the time of cell division. Cells arising from that infected cell inherit the viral genes, thereby maintaining the infection.”

Feline leukemia virus, or FeLV, a gammaretrovirus, is one of four major types of retroviruses that are known to infect domestic cats. From the time of its discovery in 1964, FeLV has been known to predispose infected cats to the development of life-threatening diseases related to anemia, cancer or immunosuppression resulting in a reduced lifespan. In recent years, however, both serosurveys and individual case reports have suggested that some cats with FeLV infections survive longer than the three to five years previously described, perhaps in part due to an effective immune response that limits the extent of the infection. In a previous study, the team identified high national support for adoption of FeLV-infected cats, even though their long-term prognosis was uncertain.

Levy’s team is performing a lifetime study of 130 FeLV-infected cats adopted from Austin Pets Alive!, an animal shelter in Austin, Texas. Now in its fourth year, the researchers used a battery of blood tests to identify clues about which cats are most likely to be long-term survivors. These new findings have cleared the way for a more streamlined and cost-effective protocol to screen cats for infection, which will help stop the spread of the disease.

The researchers used a combination of quantitative results for viral p27 antigen concentration and proviral DNA loads, to establish cutoff values to classify cats into high-positive and low-positive groups that were associated with significantly different survival times over the four-year study period. Even though the course of an FeLV infection is very much dependent on the immune status of the cat, the vast majority of cats confirmed to be infected at the beginning of the study remained infected throughout the 6-month testing period and tended to maintain their high positive (higher risk for early death) or low positive (lower risk for early death) status. These results provide new support for practical implementation of international guidelines for optimizing management of both infected and uninfected cats, including accurate diagnosis, veterinary monitoring and segregating infected cats into single-cat households or with other FeLV-infected cats.

Read the full study here.