Infectious stunning syndrome of broiler chicks I. Clinical signs and pathological lesions

Abstract

This study represented an endeavor to observe clinical signs and pathological lesions in broiler chicks suffering from experimental Infectious stunting syndrome (ISS). One hundred and twenty day old broiler chicks were divided randomly into two equal groups i.e. control (A) and inoculated (B). At day one of age each chick of the groups (A and B) was dosed with one ml of either tryptose phosphate broth or prepared inoculum respectively. Chicks of both the groups were housed separately under similar standard management. Inoculation induced characteristic clinical changes in birds of ,, treatment group like of brownish diarrhoea, lameness, feather developing problems and paleness of combs, wattles and shanks. By day-29 of the experiment all the stunted birds from group-B and an equal number of birds from group-A were slaughtered. These birds were examined thoroughly to record the gross changes in various stmcnll'es and then the severely affected organs were processed for histopathological examination. The skeletons of affected birds were britlle, keel bones showed quite prominence while the muscles and subcutaneous tissues were almost devoid of fat. Grossly it was observed that pancreas, spleen and bursa of Fabricius were severely atrophied while the intestines were ballooned with undigested feed and gases. Histopathological examination of pancreas and spleen revealed a classical picture necessary for understanding the pathogenesis of the syndrome. The acinar cells of pancreas were atrophied and underwent vacuolation, degeneration and necrosis. 1l1e zymogen granules were almost absent from the acinar cells. A characteristic change was an inflammato1y reaction in one or more pancreatic ducts where the epithelium and fibrous tissues occluded the lumen of the ducts and led to the obstmction in pancreatic drainage.