Influence of Marek's disease virus on subgroup J avian leukosis virus infection in meat-type chickens

The objective of this study was to determine the influence of various serotypes of Marek's disease viruses (MDV) on avian leukosis virus subgroup J (ALV-J)-induced viremia, cloacal shedding and tumors, in meat-type chickens. Chickens from two different breeders were placed in six different groups and infected with ALV-J at hatch; chickens were also inoculated with various strains of MDV vaccines at hatch and challenged with very virulent plus (vv+) MDV at two weeks of age.; Data from this study suggest that bivalent MD vaccines containing serotype 2 and 3 MDV, namely turkey herpesvirus and SB-1 (HVT+SB-1) may reduce viremia and cloacal shedding of ALV-J infection in one of the two strains of chickens used. Chickens infected with ALV-J and bivalent MDV vaccine had lower percentage of viremia and cloacal shedding than chickens inoculated with serotype 1 MDV vaccine (Rispens) or vv+MDV (strain 648A). In the second experiment, commercial broiler breeder chickens infected with serotype 1 MDV vaccine had the highest incidence of viremia and cloacal shedding. There was no influence of strain of MDV vaccine on ALV-J tumors.