Co-infection of Marek's disease virus with different oncogenic immunosuppressive viruses in chicken flocks.

Oncogenic tumour diseases are major threat to poultry industry. Marek's disease (MD), avian leukosis (ALV) and reticulosendotheliosis virus (REV) are the major tumour causing immunosuppressive viral diseases of chicken. A total of 120 tissue samples presented with tumour lesions from different chicken flocks of coloured broiler, layer breeders and native chicken breeds were screened for MDV, ALV and REV by histopathology and virus specific PCRs individually. Presence of oncogenic viruses in the samples were screened by virus specific PCR. A total of 47 samples were detected either with single infection or dual infection with these viruses. Out of 47, 17 were detected with either one of the viruses and remaining 30 with any of the two viruses. REV was the major cause of tumour in the present samples followed by MDV. ALV was not detected alone, it was either with MD or REV. All 5 ALV positive samples were detected with ALV-E subtype. REV was detected predominantly (22 out of 25 positives) as single infection rather than co-infection.