FeLV

FeLV, or feline leukemia virus, is a retrovirus that infects domestic cats and some wild felids. It is primarily spread through saliva during close contact such as grooming, sharing food or water bowls, or fighting, and can be transmitted from mother to kitten before or during birth. Infected cats may become persistently infected or clear the virus temporarily; persistent antigenemia carries a higher risk of disease. Young, outdoor, or multi-cat environments have higher risk.

Within the host, FeLV targets immune system and bone marrow, leading to immune suppression, anemia, and increased susceptibility to secondary infections. It can also contribute to cancer, notably lymphoma. FeLV exists in several subtypes; FeLV-A is the most readily transmitted form, while FeLV-B can emerge via recombination with the cat’s genome, and FeLV-C and FeLV-T are associated with more severe disease.

Clinical signs are variable. Some cats remain asymptomatic for years; others develop fever, reduced appetite, weight loss, lethargy, persistent infections, pale mucous membranes from anemia, diarrhea, or enlarged lymph nodes. Neoplasia, particularly lymphoma, may occur months to years after infection.

Diagnosis relies on detecting the FeLV p27 antigen in blood with an ELISA or rapid test, with confirmatory testing by IFA or PCR. A positive result generally indicates infection; negative results do not completely rule out early or regressive infection.

Management and prognosis: there is no cure. Care is supportive, focusing on nutrition, prompt treatment of infections, and monitoring. Antiviral drugs have limited efficacy. With good care, FeLV-infected cats can live for years, though they have higher illness risk and often shorter lifespans than uninfected cats.

Prevention: FeLV vaccination is available and recommended for kittens and at-risk cats, especially those with outdoor access or in multi-cat households. Preventive strategies also include routine testing, keeping infected and uninfected cats separate, and minimizing exposure to saliva-containing secretions. Regular screening in shelters is common practice.