The outcome of coronavirus infection in domestic cats depends on the strain and dose of virus, and the age, immune competence and immune status of the cat. In particular, the ability of the cat to mount a strong cell-mediated immune (CMI) response to the virus is believed to be very important in determining the clinical sequelae to infection. Thus infection can cause a wide spectrum of disease, or very often, no disease at all ( See Picture ).

This model for the pathogenesis of feline coronavirus infection explains why cats with wet FIP often have some lesions of dry FIP at necropsy, and also explains anecdotal accounts of cats recovering from wet FIP, but going on to develop dry FIP, or even (rarely) to recover.

It also explains why concurrent FeLV infection increases the prevalence of clinical FIP in a colony with FCoV infection, and suggests that treatments involving immunosuppressive agents, e.g. corticosteroids, although they might provoke a short-term general improvement in the cat's demeanour, would depress the CMI response and cause more severe disease in the long run.

The role of antibody

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