Epidemiology of a herpesvirus of turkeys: possible sources and spread of infection in turkey flocks.

Parameters of turkey herpesvirus (HVT) infection were followed sequentially from hatching through 20 weeks in two commercial turkey flocks. Maternal antibody was uniformly present at hatching but decreased below detectable levels by the 3rd week. Virus was first isolated at the 5th and 6th weeks and thereafter spread rapidly within the flocks. Development of active antibody followed that of viremia by 1 week. Both virus and antibody were present in virtually all turkeys after the 7th or 10th week; however, the incidence of tumors was negligible. Dust and litter from infected flocks were negative for HVT by poult bioassay, but the infection was easily transmitted by exposure of poults to dirty isolation cages or air from HVT-infected turkeys. Attempts to demonstrate congenital transmission of HVT by direct virus isolation from embryos of infected breeders or by isolation rearing procedures were unsuccessful.