Endemic infection of a cat colony with a feline calicivirus closely related to an isolate used in live attenuated vaccines

We have typed three feline calicivirus (FCV) isolates obtained over a 5-mon th-period from an endemically infected cat colony. Sequence analysis from v ariable region E of the capsid gene from these isolates strongly suggests t hey are minor variants of a single FCV strain. and that this strain is clos ely related to the one used in many live-attenuated FCV vaccines. Such a va ccine was last used approximately 2 months before the first of the isolates in this study was obtained. Sequence differences between the colony isolat e' and the vaccine virus suggest that the colony virus has evolved from the vaccine virus and was persisting in the colony. The extent to which vaccin e virus may contribute to the continued high prevalence of FCV needs to be deter-mined. (C) 2001 Elsevier Science Ltd. All rights reserved.