Protection against Marek's Disease by Vaccination with a Herpesvirus of Turkeys

TLDR

The study evaluated whether a turkey‑derived herpesvirus (HVT) could protect chickens against virulent Marek’s disease virus (MDHV). HVT vaccination at low doses conferred strong protection against Marek’s disease, preventing lesions for up to 20 weeks, while the virus remained nonpathogenic, noncontagious, and persisted without spreading to contact birds.

Abstract

SUMMARY Studies were conducted to determine whether a herpesvirus isolated from turkeys (HVT) would protect chickens against subsequent challenge with the virulent JM strain of Marek's disease herpesvirus (MDHV). HVT administered intra-abdominally at doses as low as 600 plaque-forming units per one-day-old chick gave protection against Marek's disease (MD). The virus would protect when birds were challenged with MDHV by intra-abdominal inoculation at 3 weeks or by contact exposure as early as 2 weeks postvaccination. Chickens inoculated with HVT and observed for 17 to 20 weeks did not develop lesions. Birds produced antibody and infection persisted throughout this period, however, as indicated by reisolation of the virus. Furthermore, HVT did not spread to chickens in direct contact with vaccinated birds. Thus HVT gives substantial protection against the development of MD yet is nonpathogenic and noncontagious, all of which are important characteristics of vaccine viruses.