Feline Leukemia Virus (FeLV): Better Diagnosis for Better Prevention

FeLV infections often go unnoticed, even by veterinarians. However, it is important to recognize the presence of the virus, as it can affect the management of cats. A new review summarizes the latest findings and methods for detecting the disease.   Feline leukemia virus (FeLV) is a retrovirus that affects domestic cats worldwide, causing a variety of symptoms such as immune deficiency, anemia, the development of tumors, secondary diseases, digestive or neurological disorders, and even leukemia. Once infected, the virus persists throughout the cat’s life. The cat will generally remain asymptomatic for a time before the onset of feline leukemia itself. For some cats, this latent phase can last months or even years. Their immune system is able to keep the virus dormant. The infection is then either arrested or in remission, and cats in this phase test negative on the screening test and are not contagious. However, these infections may eventually reactivate. For others, lacking strong FeLV-specific immunity capable of containing the virus, a progressive and frequently fatal disease sets in (50% and 80% mortality rates at 2 and 3 years, respectively). Given the impact on the patient’s health and immune system, testing for FeLV infection is strongly recommended. In addition to the need to prevent the spread of the infection from an epidemiological standpoint, a positive test result can influence the prognosis, therapeutic and epidemiological decisions, and the clinical management of each affected cat. However, diagnosing a FeLV infection remains challenging due to the different stages of the infection, which vary over time depending on the balance between the virus and the host’s immune system. Interpreting FeLV test results is not a trivial matter and requires a fundamental understanding of the disease’s pathogenesis, virus-host interactions, and the various FeLV tests and their characteristics. But technology is evolving. Diagnostic tests have become more sophisticated over the years and now incorporate various viral and immunological parameters. Combined with these new viral detection technologies, growing knowledge of the pathogenesis of FeLV infection allows for a better understanding of the virus, interpretation of test results, and thus the ability to detect the virus and more accurately determine the stage of FeLV infection, even during asymptomatic periods. A new review presents recent findings, the key characteristics to assess in FeLV infection, and commonly used methods for detecting FeLV, along with their characteristics and interpretation. In particular, it references the diagnostic algorithm developed by the European Advisory Council on Feline Diseases. The goal is to provide diagnostic expertise to enable practicing veterinarians to improve their recognition of the FeLV virus and further reduce the prevalence of the infection. Indeed, only a better understanding of this fatal feline infection and its diagnosis will make it possible to combat it effectively.