Effect of vaccination with herpesvirus of turkeys (HVT) on horizontal spread of Marek's disease herpesvirus.

Chicks were vaccinated intra-abdominally at one day old with the herpesvirus of turkeys (HVT) and challenged 3 weeks later by intra-abdominal inoculation of Marek's disease (MD) virus. Cellfree extracts of feather follicles of challenged vaccinated chicks contained MD virus but not HVT. Vaccinated chicks challenged with MD virus shed pathogenic MD virus, but not HVT, to sentinel chicks receiving exhaust air from the isolator. Vaccination reduced the amount of MD virus shed from MD-infected chickens.