Is filariasis a trigger for bronchial asthma?

Many Sri Lankan children with cough and wheeze and peripheral blood eosinophilia are treated with diethyl carbamazine (D.E.C.) on the assumption that filaria is the cause. We tried to establish whether filaria can trigger asthma and whether D.E.C. improves bronchial reactivity. In 35 symptomatic and 22 asymptomatic children peripheral blood eosinophil counts, filarial antibody test, stool examination, chest radiography, allergy skin tests and histamine inhalation tests were performed before and after treatment with D.E.C. Most of the symptomatic children were atopic; 1/3 of all children had helminthiasis, positive filarial antibodies and total eosinophil counts of greater than 2,000. Ten children had chest radiographs suggestive of tropical pulmonary eosinophilia. Only in those with intermittent symptoms was there a marked improvement in bronchial reactivity after D.E.C., but baseline peak expiratory flow (P.E.F.) improved in all symptomatic groups. We conclude that 1/3 of the children had filariasis which in an atopic individual may trigger asthma. Both the anti-inflammatory and the anti-filarial action of D.E.C. probably contribute to improvement of bronchial reactivity.