Pathological and histochemical studies on cystic echinococcosis in sheep

Pathomorphological and histochemical studies were conducted on spontaneous cases of hydatidosis in sheep in Kashmir valley. Hydatid cysts were observed in lungs (66.2%), liver (28.47%) and spleen (5.29). Both single and multiple organ involvements were recorded. Grossly cysts of varying sizes were either partially or fully embedded in tissue parenchyma. In lungs diaphragmatic lobes were mainly affected. The spleen was the least affected organ where in one spleen single multiloculated cyst was observed. The cyst wall consisted of the inner germinal, middle lamellated/laminated, and outer fibrous layer. Inflammatory reaction around the cyst was characterized by an inner zone of loosely arranged fibroblasts with sparse macrophage and mononuclear cells, followed by densely arranged fibroblasts admixed with mononuclear cells; and an outer layer of concentrically arranged fibrillar connective tissue. Fibroplasia and calcification was noted at some places. In liver besides the cellular reaction against the expanding cyst, hepatocellular degeneration and hepatocytomegaly was observed whose severity was inversely related to the distance from the cyst. Mast cell reaction was observed mainly in the inflammatory zones in the lungs while the metachromasia least evident in livers. Qualitative increase was observed for neutral and acid mucopolysaccharide and acid phosphatase activity while alkaline phosphatase activity was mild. The study showed that the hydatid cysts evoke significant inflammatory response by the host with marked histochemical responses.