Feline viral respiratory disease. The carrier state, vaccination, and control.

A thorough understanding of the epizootiology of FCV and FRTV is critical when implementing control measures in premises with enzootic URD. Failure to properly segregate cats, reduce fomite contamination, or implement a vaccination schedule most suited to that population will undoubtedly allow perpetuation of disease. Several questions remain unanswered about URD in cats. Following several years of widespread routine vaccination, what is the prevalence of the carrier state in vaccinated cats? What are the immunologic mechanisms responsible for the development of the latent FRTV carrier state and the variable level of virus excretion in FCV carriers? Why do some cats terminate primary infections with these viruses without entering a chronic carrier phase? Could immunomodulating agents be used to terminate the carrier state in persistently infected animals?