Pathogenesis of restricted movements in trichinellosis: an experimental study

Trichinellosis is a zoonosis acquired by the ingestion of insufficiently cooked pork meat containing the encapsulated larvae of Trichinella spiralis. Trichinellosis is presented with myalgia which affects various muscle groups; its intensity is usually related to the severity of the disease and may cause restriction of joint movement. However, joint pain in the course of trichinellosis could not be explained entirely by myositis. This study investigated the other possible causes of restricted movements of joints in animal model. We found that the histopathological changes in the joints of T. spiralis infected rats were in the form of inflammatory cellular infiltrates and ulceration in the synovial membrane with degeneration and ulceration of the articular cartilage. Immunohistochemical examination of the joints revealed the presence of T. spiralis local antigen or immune complex deposited in the synovial membrane. Leukocytosis and eosinophilia were observed throughout the experimental period but eosinophil level declined slowly but still elevated. In conclusion, the restricted movements during the course of trichinellosis seem to be not only due to direct invasion of muscles by the encapsulated T. spiralis larvae but also due to immune complex deposition in the joints.