ARS | Publication request: Case Report: Determining the Etiology of Unusual Tumors in Chickens

Submitted to: American Veterinary Medical Association Abstract
Publication Type: Abstract
Publication Acceptance Date: July 13, 2002
Publication Date: N/A

Technical Abstract: Two groups of 40- to 44-week-old live broiler breeder hens from one flock were submitted for determination of the etiology of visceral tumors. The flock had been vaccinated at hatch with a bivalent MDV vaccine (HVT + SB-1); mortality had increased to 1.5% per week, with a cumulative mortality of 12%. The most consistent lesion in necropsied chickens was extensive tumors involving the intestines; many birds had tumors in multiple organs. Microscopic examination of tumors revealed that the lesions were primarily lymphoblastic or myeloid in nature; lymphosarcomas, histiocytomas, and fibromas were also identified. Other tissues contained a mix of myelocytic and lymphocytic infiltrations. Additional diagnostic tests included virus isolation, PCR (for MDV, ALV-J, and reticuloendotheliosis virus), and immunohistological staining of fixed tissues. Although ALV-J was not confirmed by virus isolation or PCR, the histologic appearance of tumors suggested that ALV-J was involved. Furthermore, the isolation of serotype 1 MDV from peripheral blood lymphocytes and its demonstration by PCR in tumor tissue suggest infection with MDV. Thus, the cause of tumors in this case appears to be the result of a combined infection with MDV and ALV-J. This case illustrates the fact that standard diagnostic methods do not always produce unequivocal diagnoses, especially in cases of multiple infections.