ABSTRACT
• Most antiviral drugs available for treatment of feline and canine viral infections are nucleoside analogues with greatest activity against retroviruses, herpesviruses and coronaviruses. • Antiviral drugs also affect the function of host cell machinery;therefore, they have considerable potential for toxicity. • Antiviral drugs are widely used in human medicine for treatment of HIV infection, herpesvirus infection, and other viral. Much less is known about these medications in cats and dogs, and there are only few diseases of cats and dogs for which efficacy has been demonstrated. • There are important differences between human and animal virus infections;therefore, it should not be assumed that the use of an antiviral agent in humans can be translated to a use in animals unless there is evidence of safety and efficacy. • The most common indication for antiviral drugs in animals is treatment of FHV-1 infections with famciclovir and cidofovir. Zidovudine, an antiretroviral drug, has been used to treat FIV and FeLV infections. In addition, new antiviral drugs are now used to treat FIP. • Antiviral drugs can act synergistically with immunomodulatory agents. • Immunomodulators include microbial products, plant-derived immunomodulators, naturally occurring mammalian proteins, and synthetic drugs. The effect of many of these drugs on outcome in cats and dogs with infectious diseases has not been fully evaluated with well-designed studies. • The parenteral use of natural or recombinant human cytokines in cats and dogs can produce neutralizing antibodies after 1 to 2 weeks of treatment, which can cross-react with endogenous proteins. • Antiviral treatments are intended to suppress viral entry, multiplication, or transmission. Some of these antiviral agents can produce a remission or assist the patient's immune system to limit the course of the viral disease. © 2021 Elsevier Inc. All rights reserved.