Negative association of Enterobius infestation with asthma and rhinitis in primary school children in Taipei

BACKGROUND: The relationship between allergy and parasites has been controversial, especially in non-tropical countries. Enterobius vermicularis (human pinworm) is the most prevalent intestinal parasite in industrialized countries. OBJECTIVE: To examine the association between pinworm infestation and allergy in primary school children. METHOD: Peri-anal tape test for pinworm is routinely performed in Taipei primary schools. We collected data from school records and questionnaires distributed to all children in four primary schools grades 1 through 6 (n = 3107). RESULTS: The prevalence of physician-diagnosed asthma (9.3% vs. 14.1%, P = 0.007) and allergic rhinitis (27.4% vs. 38.3%, P = 0.001) was lower in pinworm-positive compared to uninfested children. Pinworm was not correlated with atopic dermatitis or parent allergy. With logistic regression controlling for sex, parent allergy and lower respiratory infection, current asthma (OR = 0.25, 95% CI 0.10-0.63) and rhinitis (OR = 0.61, 95% CI 0.45-0.84) were negatively associated with pinworm. Among children in grades 3-6 who had no asthma or rhinitis before age 7, those with early infestation (pinworm diagnosis at or before grade 1) had a lower risk of having diagnosis of rhinitis during school years, compared to the uninfected group (5.4% vs. 12.3%, P = 0.03; adjusted OR = 0.47, 95% CI 0.21-1.02). CONCLUSIONS: We identified a negative association between pinworm infestation and allergic airway diseases, which could in part be attributed to protective effect of pinworm infestation on development of allergic symptoms. Other mechanisms of association could not be ruled out.