Feline infectious peritonitis (FIP), which is caused by certain strains of feline coronavirus, is a progressive and usually fatal disease for which there is currently no cure or effective treatment. It is a disease which continues to challenge vets and its diagnosis is a crushing blow to owners who will inevitably lose their cherished cats.
There is an important and unique immunological component to the pathology of the disease and there is evidence that some immunosuppressive drugs may offer hope. However, current treatments may induce short-term remission in a small percentage of cats.
Cyclosporin A (CsA) has recently been shown to exert potent antiviral activities in several in vitro systems, including against coronaviruses. However, whether CsA has clinically relevant activity against coronaviruses remains unknown.
Yoshikazu Tanaka and colleagues report a case of effusive FIP in which treatment with CsA resulted in a sustained reduction in viral copy number and pleural fluid volume and was accompanied by clinical improvement.
A 14-year-old female domestic shorthair cat was presented with persistent fever, anorexia and jaundice for a month. A general clinical examination showed a substantial pleural effusion, and laboratory investigation revealed a significant feline coronavirus antibody titre and a low packed-cell volume, as well as signs indicative of liver damage. Pleural fluid was yellowish, viscous and remarkably dense. Coronavirus antigen was demonstrated within macrophages in the pleural fluid and real-time quantitative reverse transcription PCR (RT-qPCR ) revealed 1.6×10 6 copies/ml in pleural fluid, which is higher than that in other cases of effusive FIP that the authors had encountered. The diagnosis of FIP was based on the clinical presentation and clinicopathological, cytological and RT-qPCR findings.
Type-I interferon treatment for two months did not result in improvement in pleural fluid volume and viral copy number and treatment was stopped. Following discussion with the owner, treatment with a daily dose of modified cyclosporin A (CsA) was started. The volume of pleural fluid decreased and became undetectable within four days of starting CsA therapy. The condition of the cat improved, it became more alert and regained a normal appetite, and therefore CsA administration was stopped. However, the pleural fluid accumulated within four days of stopping CsA treatment. Treatment was recommenced and again the pleural fluid levels disappeared and the viral load decreased substantially. Over a two-month period, during which a low dose of CsA was maintained, no clinical abnormalities were detected, the anaemia resolved and biochemical parameters returned to normal.
Unfortunately, about two months after CsA treatment was stopped, viral load gradually increased but no clinical abnormalities were detected until about seven months after treatment was stopped. The cat’s clinical condition deteriorated and it died shortly after.
The study suggests that the potential therapeutic effects of CsA in combination with other therapeutic agents should be evaluated.
Full details of the investigations carried out, treatment and outcome can be found here.