Skeletal muscle pathology in mice experimentally infected with Toxoplasma gondii

In two different groups of mice, the infection with Toxoplasma gondii was produced by intraperitoneal route, with 2 x 10(5) parasites (n = 8) and 14 x 10(5) parasites (n = 3). Five days after infection animals were killed to examine skeletal muscles by light and transmission electron microscopy. Severity of muscle alterations depended upon concentration of parasites. Parasite cysts were not identified in muscle sections. Ultrastructural features revealed different degrees of fibre atrophy, alterations in the sarcomeric structure and, in some cases, disorganization of contractile and sarcotubular systems. Changes in muscular capillaries included loss of the endothelial wall, occlusion of lumen and necrosis. Motor end-plates were abnormal and axonolysis was present. A mononuclear cell infiltrate consisted of macrophages, lymphocytes, mastocytes and eosinophils were observed. In this murine model it was demonstrated that the infection of non-immunocompromised hosts with Toxoplasma gondii produces an acute myositis.