Pathogenesis of Feline Coronavirus Infection

Pedersen, N.C., C.E. Allen, and L.A. Lyons, Pathogenesis of feline enteric coronavirus infection. Journal of Feline Medicine & Surgery, 2008. 10(6): p. 529-541.

The importance of feline enteric coronavirus (FECV) as a primary intestinal pathogen is considered minimal. The importance of FECV is that this virus can mutate in vivo. At least one mutant form causes the highly fatal disease called feline infectious peritonitis (FIP). Initially, this study had been designed to demonstrate that resistance and susceptibility to FECV infection were under genetic control, just as genetics appear to play a significant role in FIP resistance. With more than 3 years of study results, it became apparent that genetics would not readily define this initial goal. The investigators made a decision to concentrate their efforts on what was learned about FECV pathogenesis. A distinct primary stage of infection was identified that lasted from 7 to 18 months, with the highest level of virus shedding during this phase. This primary stage resolved in one of the three following ways: 1) recovery, 2) persistent shedding, or 3) recurrent or intermittent shedding. During the primary phase, shedding levels were significantly higher in kittens than in adult cats. As kittens might be infected before their immune systems mature, FECV replication would be more frequent and increase the potential for FECV to FIP mutations. FIP is known to be more common in kittens than adult cats. The investigators also looked at the role of stress on reactivating latent or subclinical infection, or increasing virus shedding. They evaluated the role natural stress such as pregnancy, parturition, and lactation might play. Stress was also simulated by giving a series of corticosteroid injections using methylprednisolone acetate. No increase in virus shedding was reported in any of the scenarios. Virus shedding and serum antibody titers had a significant relationship to each other. Cats shedding virus usually had titers of 1:100 or higher. Cats that were not shedding virus usually had titers of 1:25 and lower. Additional observations on immunity to FECV infection found that immunity during the primary phase of infection was slow to develop, intermittent, and tenuous in duration. Immunity during re-infection tended to mirror that occurring during primary infection, indicating this immunity lacks memory. This pattern of infection and immunity is strongly influenced by environmental factors. [MK]
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Pedersen, N.C., A review of feline infectious peritonitis virus infection: 1963-2008. Journal of Feline Medicine & Surgery, 2009. 11(4): p. 225-258.
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Addie, D., et al., Feline infectious peritonitis ABCD guidelines on prevention and management. J Feline Med Surg, 2009. 11(7): p. 594-604.
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