CHRONIC URTICARIA AND TOXOCARA-CANIS INFE CTION - A CASE-CONTROL STUDY

Introduction. The cause of chronic urticaria remains unknown very ofte n. Having noted several cases of chronic urticaria associated with ant ibodies to Toxocara canis, and lacking any other explanation, we set-u p a case-control study. Patients and methods. Between November 1992 an d April 1993, 51 adults or children with chronic urticaria (cases) who had been examined al least once at one of the three dermatology units of the Bordeaux University Hospital were matched to controls who had neither signs nor symptoms of chronic urticaria. The presence of antib odies to T. canis was measured by ELISA and Western blot. Results. The frequency of T. canis was 64.7 p. 100 in cases and 21 p. 100 in contr ols (p < 0.0001) with an odds ratio of 6.9 (95 p. 100 CI: 2.9-16.3). C ases with antibodies to T. canis were more frequently in contact with pets (84 vs 50 p. 100, p < 0.001). Of the 33 cases of chronic urticari a with antibodies to T. canis, 14 have been treated with thiabendazole or ivermectin and after a one-year follow-up, 5 (36 p. 100) were cure d and 4 (29 p. 100) had improvement. No improvement occurred in the 12 /19 cases not specifically treated. Conclusion. The strong association between the presence of antibodies to Toxocara canis and chronic urti caria is unlikely to be due to chance. A causal relation is difficult to establish, however. Our findings should prompt further investigatio n of a role for Toxocara canis in chronic urticaria and the evaluation of therapeutic interventions. Preventive measures include deworming p ets (dogs particularly), enclosing kitchen gardens, and handwashing be fore meals. A systematic measure of Toxocara canis in patients with ch ronic urticaria is recommended especially when in contact with dogs. E arly and specific treatments can be applied on knowledge we already ha ve.