Efficacy of antiviral chemotherapy for retrovirus-infected cats: What does the current literature tell us?

Abstract

The two feline retroviruses, feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV), are global and widespread, but differ in their potential to cause disease. FIV, a lentivirus that shares many properties with human immunodeficiency virus (HIV), can cause an acquired immune deficiency syndrome, which predisposes cats to other infections, stomatitis, neurological disorders and tumours. Although secondary infections are common, specific opportunistic infections or acquired immunodeficiency virus-defining infections, such as those that occur with HIV, are not commonly reported in FIV-infected cats. In most naturally infected cats, FIV does not cause a severe clinical syndrome; with appropriate care, FIV-infected cats can live many years before succumbing to conditions unrelated to their FIV infection. Thus, overall survival time is not necessarily shorter than in uninfected cats, and quality of life is usually high over many years or lifelong. FeLV, an oncornavirus, is more pathogenic than FIV. Historically, it was considered to account for more disease-related deaths and clinical syndromes in cats than any other infectious agent. Recently, the prevalence and importance of FeLV have been decreasing, mainly because of testing and eradication programmes and the use of FeLV vaccines. Progressive FeLV infection can cause tumours, bone marrow suppression and immunosuppression, as well as neurological and other disorders, and leads to a decrease in life expectancy. However, with appropriate care, many FeLV-infected cats can also live several years with a good quality of life. A decision regarding treatment or euthanasia should never be based solely on the presence or absence of a retrovirus infection. Antiviral chemotherapy is of increasing interest in veterinary medicine, but is still not used commonly. This article reviews the current literature on antiviral chemotherapy in retrovirus-infected cats, focusing on drugs that are currently available on the market and, thus, could potentially be used in cats.