Pathological, Histochemical and Immunohistochemical Studies of Lungs and Livers of Cattle and Sheep Infected with Hydatid Disease

Abstract

This work was carried out to study the pathological changes in the lungs and livers with hydatid disease of slaughtered cattle and sheep. Lungs and livers of 521 cattle and 675 sheep were examined. Infection rates of 4.8% and 1.8% were recorded in cattle and sheep, respectively. The predilection sites in cattle were the lungs and the livers, while in sheep cysts were only found in the livers. In cattle, lung and liver, cysts were mostly of medium size (2–4 cm), but large cysts (> 4 cm) were, also, observed, while most of sheep liver cysts were small in size (< 2 cm). The amount of fluid from hydatid cyst of cattle ranged from 0.2 to 50 ml; only one cyst contained 600 ml. In sheep, the cyst contained small amounts of liquid with a maximum of 3 ml. The fertility rates of the cysts were 23.4% and 11.1% in cattle and sheep, respectively. Cyst sections from infected lungs of cattle showed laminated membranes surrounded by a zone of cellular infiltration of mainly lymphocytes, plasma cells, macrophages and rarely neutrophils, eosinophils and giant cells and the outermost fibrous tissue reaction. Calcification was, also, observed. The neighbouring tissues showed atelectasis, emphysema, haemorrhage, congestion and fibrosis. Sections from the second, third and fourth centimeters away from the cyst walls showed similar but less pronounced pathological reactions. In liver cyst sections, the pathological changes were almost similar to that observed in the lungs with atrophy and necrosis of hepatocytes. Immunohistochemical studies revealed that all slides stained with markers for CD³ and CD²º showed positive reaction for CD³ and negative for CD²º. This finding suggests that the cellular reaction in the hydatid cyst wall consists mainly of T-lymphocytes. In all liver and lung sections from cattle and sheep stained with Masson’s trichrome stain, and fibrous tissues in the hydatid cyst capsules or around blood vessels and air passages stained green. The acellular laminated membranes and the protoscolices, also, stained green. In hydatid cyst sections from cattle and sheep stained with Periodic Acid Scheff (PAS), and laminated membranes, germinal layers and protoscolices took positive PAS magenta colour. It is concluded that the presence of cyst in an infected organ causes pathological changes in tissues around the cyst and further away from the cyst. It is, also, concluded that T-lymphocytes (CD³ positive cells) appear to dominate the mononuclear infiltrate as demonstrated by immunohistochemistry. This indicates that T. lymphocytes play a role in immunological reaction against hydatid cyst.