Clinical and virological evaluation of the efficacy of an inactivated EHV1and EHV4 whole virus vaccine (Duvaxyn EHV1,4). Vaccination/challenge experiments in foals and pregnant mares

Pregnant mares and young foals were vaccinated with Duvaxyn EHV1,4, an inac tivated and adjuvanted vaccine containing both the EHV-1 and 4 antigens. SN and CF antibody titres were induced two weeks after first vaccination. Ant ibody levels were boosted after second vaccination, however they never reac hed the levels induced after virus challenge. Young foals were challenged w ith virulent EHV-1 and EHV-4 field viruses. Pregnant mares were challenged with the highly abortigenic EHV-1 strain AM. Vaccinated animals showed a cl ear reduction in clinical signs and virus excretion compared to unvaccinate d control animals. Log transformed antibody levels could be correlated to d uration of virus excretion. The incidence of EHV-1 induced abortions was dr astically reduced in vaccinated mares. Therefore, although vaccinated anima ls are not fully protected against disease, Duvaxyn EHV14 clearly reduces c linical symptoms, the duration of virus shedding and the quantity of virus shed. It can be concluded that vaccination of foals and pregnant mares with Duvaxyn EHV1.4 significantly reduces the risk of abortions and outbreaks o f respiratory disease caused by circulating field viruses. (C) 2001 Elsevie r Science Ltd. All rights reserved.