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Feline leukemia virus review provides update on pathogenesis and diagnosis

It is recommended that the FeLV status of every cat is known

A review published in the Journal of Feline Medicine and Surgery aims to contribute diagnostic expertise to veterinarians in practice by reviewing recent insights into feline leukemia virus (FeLV) infection pathogenesis, gained using molecular techniques.

Professors Regina Hofmann-Lehmann, of the University of Zurich, Switzerland, and Katrin Hartmann, of LMU Munich, Germany, explain that not only are there several different outcomes of FeLV infection, but that these can vary over time. Newly classified as 'progressive', 'regressive', 'focal' and 'abortive' infection, the authors describe how it can be helpful to think of these outcomes in terms of a set of balance scales, with the cat's immune response on one side and the virus on the other.

From an epidemiological point of view, it is the progressively infected cat that is most significant. In these infections, the virus has the upper hand - these cats shed high numbers of FeLV particles and pose an infection risk to other cats. Regardless of their health status, progressively infected cats need to be kept apart from FeLV-naïve companions. From a clinical point of view, progressively infected cats are a priority too: they are at high risk of succumbing to potentially fatal disease; though, if well cared for, many can continue to live a healthy and happy life, sometimes for years.

Of the other possible outcomes, abortive infection is the most favourable for the cat - these cats have strong anti-FeLV immunity. Regressively infected cats will have developed a partially effective antiviral immune response that can keep the virus in check; however, they probably never clear the infection completely, and can shed virus, and thus pose an infection risk, in the early phase of infection or if reactivation occurs. In focal infection, which is comparatively rare, the cat's immune system keeps viral replication sequestered in certain tissues.

When it comes to FeLV testing, seemingly perplexing or 'discordant' test results are not uncommon, particularly in the early phase of infection, and can pose considerable challenges for the practitioner needing to establish the FeLV status and implement appropriate therapeutic and epidemiological measures. The authors discuss the most frequently used methods for FeLV detection, including free FeLV p27 antigen testing, viral RNA testing and FeLV provirus testing, focusing on when to test and how to interpret a positive or a negative result. The detection of anti-FeLV antibodies, including a point-of-care test for FeLV p15E introduced recently onto the European market, is also discussed. A diagnostic algorithm produced by the European Advisory Board on Cat Diseases (ABCD) that provides guidance on which test to choose in which scenario is incorporated within the review article.

As well as being expert members of the ABCD, both authors were members of an expert panel for consensus guidelines from the American Association of Feline Practitioners (AAFP) on feline retrovirus testing and management and together the guidelines and review article present the current state of knowledge about this virus.


Hofmann-Lehmann, R., Hartmann, K. (2020). Feline leukaemia virus infection: A practical approach to diagnosis. Journal of Feline Medicine and Surgery, 22(9), 831-846, doi: 10.1177/1098612X20941785

Little, S., Levy, J., Hartmann, K., Hofmann-Lehmann, R., Hosie, M., Olah, G., Denis, K. S. (2020). 2020 AAFP Feline Retrovirus Testing and Management Guidelines. Journal of Feline Medicine and Surgery, 22(1), 5-30, doi: 10.1177/1098612X19895940

Article details

  • Date
  • 10 September 2020
  • Source
  • SAGE
  • Subject(s)
  • Dogs, Cats, and other Companion Animals