Feline Leukemia Virus (FeLV) - Literature review

SUMMARY Background: Continuing the series on the most important feline pathogens in the Retroviridae family, the authors describe the aetiology, epidemiology, pathomechanism, clinical findings, diagnostics, therapy and prevention of Feline leukemia virus (FeLV). Aetiology, epidemiology: Feline leukemia virus is a virus in the Gammaretrovirus genus, Orthoretrovirinae subfamily, Retroviridae family. It is a worldwide spread pathogen, formerly causing one-third of deaths of domestic cats. Nowadays due to successful screening attempts and vaccination, prevalence of FeLV has decreased to 1–8%, however, it can be significantly higher among free-roam cats. Transmission requires close contact, generally occurring via fighting, biting and social contact, but also vertical transmission from queen to kittens is possible in utero or with milk. Patomechanism: FeLV first replicates in regional lymphoid tissues after infection, then it is causing viraemia if the cat is immunocompetent. Beside the importance of cat’s immunostatus and age, severity of infection depends on the pathogenicity and titre of virus. Forms of disease can be progressive, regressive, abortive and atypical. Clinical findings: As it was discussed in the case of Feline immunodeficiency virus, main clinical findings are general, not informative, usually during the viraemic phase: lethargy, anorexia, fever and malaise. However, in case of FeLV, haematopoietic disorders, neoplasia are strongly connected to the progressive disease, thus anaemia (90% non-regenerative), leukemia, lymphoma are frequently seen. Secondary infections also can happen due to immunosuppression, and rarely neuropathy, reproductive disorders are diagnosed. Diagnostics: Different approaches are available for the diagnostic. The most commons are ELISA-type tests and PCR methods (mostly used for confirmatory testing or research intents). Treatment: As in the case of FIV, we are not able to eliminate the pathogen from the body, only to alleviate the symptoms and treat secondary diseases. Prevention: There is a commercially available recombinant vaccine, which is highly effective, and had an enormous role in the eradication of the virus from cat populations