UNUSUAL GROSS PRESENTATION OF SARCOCYSTIS-LIKE PECTORAL MUSCLE LYMPHOMA ATTRIBUTED TO MAREK'S DISEASE IN A BACKYARD CHICKEN

Marek's disease induced lymphomas of skeletal muscle are rarely reported in chickens. Three mixed-breed, adult backyard chickens, which belonged to a flock with a previous history of anorexia, depression, ruffled feathers, whitish diarrhea, weight loss and death, were submitted for postmortem examination and diagnostic testing. Grossly, 2 birds had moderate pectoral atrophy, whereas the remaining chicken had numerous white, rice-grain sized foci distributed throughout the pectoral musculature. Severe proventricular wall thickening was observed in all 3 chickens and moderate intestinal Ascaridia spp. parasitism was diagnosed in 2 of the birds. Microscopically, the peripheral nerves, cerebrum, proventriculus, and pectoral musculature were severely infiltrated by mononuclear pleomorphic cells. Forma1in-fixed, paraffin-embedded tissues from all 3 chickens were polymerase chain reaction positive for Marek's disease virus. A diagnosis of Marek's disease was based on the combined necropsy, histopathology, and polymerase chain reaction findings. This article describes the unusual gross presentation of rice-grain sized and shaped lymphomas in the pectoral musculature of chickens caused by Marek's disease. Copyright (C) 2017 Elsevier Inc. All rights reserved.