Lack of an association between hydatid disease and autoimmunity.

The prolonged survival of Echinococcus granulosus within the human host indicates that some mechanism is operating to permit parasite evasion of the host immune response. Several publications have described autoimmune phenomena in patients infected with hydatid cysts. The aim of this study was to test the postulate that there is a higher prevalence of autoantibodies in serum from patients with hydatid disease than in control samples, and this may provide some evidence of an association between autoimmunity and E. granulosus infection. Sera from 70 patients with hydatid disease and 45 control subjects were assayed for the presence of antinuclear antibodies (ANA), tissue specific autoantibodies and rheumatoid factor. All patients were aged between 20 and 80 years of age with no known history of autoimmune disease. Hydatid patients were surgically confirmed cases. Control subjects were chosen on the basis that they were age and sex matched to the test sera and had no known illness at the time blood samples were obtained. On the basis of an ANA autoantibody titre of > 1:40 being regarded as positive, 19 (27%) of the hydatid patients, 13 (28%) of the controls were positive. Low levels of tissue specific autoantibodies and rheumatoid factor were detected in sera from 5 (7%) and 2 (11%) hydatid patients and 4 (8%) and 3 (16%) of control subjects respectively. No significant differences (P > 0.05) were found between autoantibody levels in the hydatid patient sera and the controls. These findings suggest that there is no association between hydatid infection and the level of autoantibodies to a broad range of self antigens.