The epidemiology of avian herpesviruses in veterinary medicine.

There are ten avian herpesviruses, which have been isolated from eight orders. Six of these are of veterinary importance: Pacheco's parrot disease virus, pigeon herpesvirus, duck plague virus, infectious laryngotracheitis virus, herpesvirus of turkeys and Marek's disease virus. The knowledge on the epidemiology of each virus and the disease it causes is discussed. Features in common to infections with most avian herpesviruses are: infection is persistent in individuals and ubiquitous in populations; virus is shed for long periods of time after infection although in some cases erratically; infection does not necessarily result in disease and at least in some avian herpesvirus infections the incidence of disease is affected by the pathogenicity of the virus; the genetic constitution of the host and stress factors affecting the host. It is concluded that man's interference with the natural history of host species often increases the threat and incidence of disease unless preventive action is taken.