Wirusy onkogenne u drobiu. Część III. Wirus choroby Mareka

Abstract

Chickens are the most important natural host for Marek’s disease virus (MDV),cell-associated but readily transmitted alphaherpesvirus with lymphotropicproperties of gammaherpesviruses. Marek’s disease is a highly contagiousviral disease of poultry characterized by T-cell lymphomas and peripheral nerveenlargement. Marek’s disease is one of the most ubiquitous avian infectionsand is identified in chicken farms worldwide. Every flock, except for thosemaintained under strict pathogen-free conditions, is presumed to be infected.Marek’s disease readily transmitted among chickens. The virus matures intoa fully infective, enveloped form in the epithelial cells of the feather follicle,from which it is released into the environment. It may survive for months inpoultry house litter or dust. Dust or dander from infected chickens is particularlyeffective in transmission. Once the virus is introduced into a chicken flock,regardless of the vaccination status, infection spreads quickly from bird to bird.Infected chickens continue to be carriers for long periods and act as sourcesof MD virus. Shedding of infectious virus can be reduced, but not prevented, byprior vaccination. MDV not vertically transmitted. Although clinical cases arenot always apparent, a subclinical signs as decrease in growth rate and in eggproduction, may be economically important. Currently available vaccines areconsidered as protective