Limited efficacy of topical recombinant feline interferon-omega for treatment of cats with acute upper respiratory viral disease.

Despite a lack of controlled studies confirming its efficacy, recombinant feline interferon-omega (rfeIFN-ω) is used in the treatment of feline upper respiratory tract disease (FURTD), which is usually caused by feline calicivirus (FCV) or feline herpesvirus-1 (FHV-1). The aims of the present study were to investigate whether administration of rfeIFN-ω improves clinical signs in cats with acute FURTD and whether this treatment reduces shedding of FCV. Thirty-seven cats affected with acute FURTD were recruited into a prospective, randomised, placebo-controlled, double-blinded clinical trial. The presence of FCV and/or FHV-1 was determined by performing quantitative polymerase chain reaction (qPCR) on oropharyngeal and conjunctival swabs. Cats were randomly assigned to treatment groups, receiving either placebo or rfeIFN-ω (2.5 MU/kg) subcutaneously, followed by 0.5 MU topically at 8-h intervals via the conjunctiva, intranasally, and orally for 21 days. All cats received additional treatment with antibiotics, expectorants, and inhalation of nebulised physiological saline with camomile. Clinical signs and FCV shedding were evaluated over 42 days. All cats demonstrated improvement in clinical signs during the course of the study, with no significant difference in any of the assessed variables when comparing the two groups. FCV copy numbers decreased more rapidly in cats receiving rfeIFN-ω. Treatment with rfeIFN-ω was not effective in ameliorating clinical signs of acute viral FURTD compared to placebo, but might accelerate a reduction in FCV load in infected cats.