Feline leukaemia virus (FeLV) infection in domestic pet cats in Australia and New Zealand: Guidelines for diagnosis, prevention and management.

Progressive feline leukaemia virus (FeLV) infection dramatically shortens the lives of infected cats, causing acquired immunodeficiency, aplastic anaemia, lymphoma, leukaemia and other myeloproliferative diseases. The potential impact of regressive FeLV infection on the development of disease remains largely unknown, although there is evidence it contributes to lymphoma development. Despite a perception that there has been a general decline in the incidence of progressive FeLV infection in Australia and New Zealand, it remains an important health threat and the risk of infection should not be ignored. Clinicians should therefore have a thorough understanding of the complexities surrounding the diagnosis, management and prevention of this disease. Point-of-care (PoC) antigen testing using whole blood is the first step to detect progressive FeLV infection. Clinicians should remember the increased rate of false-positive results using such kits when the disease being detected is at a low prevalence. We therefore advise that confirmatory FeLV polymerase chain reaction (PCR) testing to detect proviral DNA is essential before a PoC-positive cat can be confirmed as being FeLV-infected. Critically, progressively infected cats should not be euthanased because of a positive FeLV diagnosis, as some cats will remain healthy for many years. Regressively infected cats should not be used as blood donors, so blood donor programmes should include FeLV antigen and provirus PCR testing in their standard screening protocols. No cure currently exists for progressive or regressive FeLV infection; therefore, veterinarians should advocate to minimise the exposure of cats to FeLV as a first-line preventative strategy. The most reliable way to achieve this is for cats to be kept indoors, or with secured outdoor access (e.g., cat enclosures and secure gardens). Cats kept in this manner do not require FeLV vaccination. All animal holding facilities should aim to individually house untested adult cats to limit the spread of FeLV infection. For at-risk cats that cannot be kept indoors/enclosed, or for cats that live together with known FeLV-infected cats, vaccination should be undertaken. Two pentavalent vaccines containing inactivated whole-FeLV are currently available in Australia, whereas no FeLV vaccine is currently available in New Zealand. Given the unavailability of monovalent FeLV vaccines, we endorse the use of a pentavalent vaccine in Australia only in FeLV-endemic catteries or in situations where there is a demonstrable and substantial risk of FeLV exposure. Manufacturers are encouraged to reintroduce efficacious monovalent FeLV vaccines in Australia and New Zealand. Further research into potential antiretroviral therapy to treat FeLV infections in cats is needed.