Atopy, intestinal helminth infection and total serum IgE in rural and urban adult Gambian communities

Background The rarity of atopy in traditional societies has been attributed to high parasite-driven blocking IgE concentrations. Information is lackin g on the relationship between atopy, IgE and intestinal helminth infection in African populations. Objective To determine the prevalence of atopy and intestinal helminth infe ction and to relate these to wheeze history and serum total IgE in a commun ity sample of adults from an urban (Banjul) and a rural (Farafenni) area of the Gambia. Methods Six hundred and ninety-three adults were interviewed about respirat ory symptoms using a modified version of the IUTLD questionnaire, and had s kin prick testing using four allergens. Stools were examined after formol-e ther concentration. Total serum IgE concentration was measured in a subset of participants. Results The prevalence of atopy (mean weal diameter > = 3 mm) in the urban and rural area was 35.3% and 22.5% (P=0.05); D. pteronyssinus and Mold mix being the common sensitizing allergens. Prevalence of wheeze in the previou s 12 months was 4.4% and 3.5% for the urban and rural areas, respectively. Wheezing was not significantly associated with atopy. Seventeen per cent of urban and 8.2% of rural subjects had helminths detected in stools. There w as an inverse association between atopy and intestinal helminth infection; 7% of atopic subjects had helminths, compared to 13% of non-atopic subjects (unadjusted odds ratio 0.51, 95%CI 0.24-1.1, P=0.09; adjusted odds ratio 0 .37, 95%CI 0.15-0.92, P=0.03). Non-atopics had total serum IgE concentratio ns about 2.5 times the upper limit of the reference range in non-atopic Wes tern populations. Geometric mean total serum IgE concentration was signific antly higher among atopic subjects (570 IU/mL, IQR 91-833) than non-atopic subjects (259 IU/mL, IQR 274-1303) (P<0.001). IgE concentration was not ass ociated with the presence of helminth infection. Conclusion Further studies are needed to clarify why asthma is still relati vely uncommon in spite of the prevalence of atopy in Gambian adults. Our da ta are also compatible with the idea that atopy might protect against helmi nth infection.