Detecção e caracterização molecular do vírus da doença de Marek em Minas Gerais

Abstract

Marek disease virus (MDV) is an infectious agent that affects primarily domestic chickens (Gallus gallus domesticus), both of industrial poultry farming as of subsistence, causing a lymphocytic inflammatory disease-known as proliferative Marek disease (MD). The disease causes in productive and economic losses to poultry, but also impact the poultry. The occurrence of MD was reduced dramatically with the use of mandatory vaccination of hatchery chicks since the years 1970. The emergence of strains of high and very high virulence of MD virus (MDV), however, was reported in several countries, involved in outbreaks in vaccinated flocks. However, in spite of Brazil being the world's largest exporter of chicken meat, no known molecular genetic profile of MDV. Describes the molecular characterization of MDV strains based on sequencing of the gene encoding the protein Meq of MDV, in chickens of subsistence and industrial poultry farming of Belo Horizonte and metropolitan region. Birds with clinical picture suggestive of DM were admitted in the laboratory of poultry Diseases and examined. A total of 112 birds positive for MDV, fifteen (13.4%) isolates with pathogenic potential were detected, two being characterized as high virulence MDV (vvMDV), and the remaining thirteen isolates were characterised as MDV virulent (vMDV) classics. The presence of vvMDV strains may represent increased risk of failure of vaccine protection in industrial stocks. However, in the vast majority of birds (86.6%) was not detected MDV pathogen. A total of 112 chickens positive for MDV, 75 birds presented a painting of simultaneous infection between MDV and one or more infectious agents. The scenario of concurrent infections or coinfecções between MDV and other endemic agents suggests be representative of common condition on epidemiology of infections in birds. Molecular characterization of MDV and co-infection by some important infectious agents is discussed.