Pathology of sudden death syndrome in chickens: Report on associated pectoral muscle lesions

A private broiler chicken farm reported 2.5% mortality per day in apparently healthy birds with clinical signs of sudden death and found upside down.Postmortem examination revealed oedema of lungs, congestion of spleen and kidney, mottling of liver and highly contracted ventricles and clotted blood-filled auricles of heart.Representative tissue samples were collected in 10% formalin for histopathology.Microscopically, heart revealed MNC infiltrations with vacuolar changes in myocardial fibers.Pectoral muscles revealed muscle fiber swelling, fragmentation, degeneration, vacuolation and myofibril flocculation within sarcolemma.Cardiac tachyarrhythmia was proposed to be the cause of death predisposed by various factors.This study described the gross and microscopic pathology and prominent pectoral muscle lesions for the first time in SDS affected birds and elaborated on various possible factors for the cause of sudden cardiac arrest.