Feline immudeficiency virus subtypes B and A in cats from São Luis, Maranhão, Brazil.

Feline immunodeficiency virus (FIV) is a retrovirus of the genus Lentivirus that is distributed worldwide, with prevalence rates varying between 2.5% and 44%. FIV causes immunosuppression, with depletion of TCD4 lymphocytes, with the majority of clinical signs caused by secondary and opportunistic infections.