Morphological aspects and pathological impacts of cystic echinococcosis in liver of slaughtered sheep and host-parasite relationship

Cystic echinococcosis (CE) is a parasite-borne disease caused by the larval stage of Echinococcus granulosus belonging to family Taeniidae, is an endemic disease, distributed worldwide as a neglected parasite with socioeconomic repercussions. It causes severe alterations in liver of infected host, and it could be fatal if untreated. The main objective of the present study is to measure and evaluate the condition of hydatidosis in slaughtered sheep in Al Baha region, Saudi Arabia. A total of 601 slaughtered sheep in Al Baha abattoirs were examined for hydatidosis during the year 2020. Various organs were examined for the presence of parasite cysts, and the cyst contents were examined by light microscopy. Also, liver sections infected with cysts were examined for pathological alterations and host-parasite interactions. Forty-two animals were infected (6.09%) with the highest prevalence during summer. During gross examination, it was observed that the sheep liver is the most affected organ by the disease. The liver contained multiple cysts with varying sizes, filled with clear to slightly turbid fluid containing protoscoleces. Detailed sections of the infected liver revealed significant fibrosis around the central vein, portal vein congestion, infiltration of inflammatory cells, and necrosis. Sections through hydatid cysts showed the presence of three surrounding layers with a laminar membrane bordering the cyst lined by a germinal epithelium surrounding several brood capsules with many protoscolesces inside supported by a set of rostellar hooklets. Considerable efforts should be spent to control the transmission of parasitic cysts and inhibit the incorrect disposal of infected meat from slaughterhouses. Also, more focus should be done on epidemiological and control programs of these parasites.