AN EPIZOOTIC OF FELINE HERPESVIRUS, TYPE-1 IN A LARGE SPECIFIC PATHOGEN-FREE CAT COLONY AND ATTEMPTS TO ERADICATE THE INFECTION BY IDENTIFICATION AND CULLING OF CARRIERS

This study describes the clinical course of an inadvertent feline herp esvirus, type 1 (FHV-1) outbreak in 2 specific pathogen-free (SPF) res earch and breeding colonies housing 690 cats and assesses a programme that was designed to eradicate the virus from the colonies. The clinic al signs observed in these cats were milder, with more eye involvement than those previously described for FHV-1 infection and did not inclu de abortion. FHV-1 eradication was based on the detection and eliminat ion of both active and latent viral carriers. Carrier cats were detect ed by virus isolation from oral swabs before and after corticosteroid- induced reactivation of FHV-1 excretion. Four per cent of recovered ca ts were actively shedding virus prior to corticosteroid treatment; 21% of the virus negative cats shed virus after one corticosteroid inject ion, and 12% of remaining culture negative cats tested positive upon a second corticosteroid treatment 6 weeks later. The colony remained vi rus free for 8 months after all detectable virus carriers were culled and there was no seroconversion among new kittens. A second epizootic of FHV-1 then occurred among susceptible animals. At this time, all br eeding cats that had tested negative after 2 injections of corticoster oids were treated a third time; 23% of them now tested positive for FH V-1. This study demonstrates that corticosteroid treatment can be usef ul in improving the rate of detection, essential as a basis for decrea sing the incidence of enzootic disease, but it is unlikely to detect a ll possible FHV-1 carriers in large populations of cats.