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Notes: Background The rarity of atopy in traditional societies has been attributed to high parasite-driven blocking IgE concentrations. Information is lacking on the relationship between atopy, IgE and intestinal helminth infection in African populations.Objective To determine the prevalence of atopy and intestinal helminth infection and to relate these to wheeze history and serum total IgE in a community 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 respiratory symptoms using a modified version of the IUTLD questionnaire, and had skin prick testing using four allergens. Stools were examined after formol-ether 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 previous 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 was 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 concentrations about 2.5 times the upper limit of the reference range in non-atopic Western populations. Geometric mean total serum IgE concentration was significantly 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 associated with the presence of helminth infection.Conclusion Further studies are needed to clarify why asthma is still relatively uncommon in spite of the prevalence of atopy in Gambian adults. Our data are also compatible with the idea that atopy might protect against helminth infection.

Notes: Background Asthma is reported to be rare in traditional rural communities, but is thought to be increasing as lifestyles become more urbanized or ‘western’.Objectives A community-based survey of non-communicable diseases was conducted from October 1996 to June 1997, and included comparison of the prevalence of asthma, smoking and chronic cough in rural and urban Gambia.Methods A cluster sample survey was conducted in a random sample of rural and urban adults (≥ 15 years of age). Subjects were asked about respiratory symptoms using a locally adapted version based on the IULTD questionnaire. Spirometry (basal, methacholine provocation and reversibility with a bronchodilator) and skin prick tests were performed on a randomly selected subsample of all subjects and those who, when interviewed, said they wheezed or had been diagnosed as asthmatic by a doctor.Results Out of 2166 participants in the urban population, 4.1% reported having had wheezing or whistling in the chest in the previous 12 months, 3.6% reported doctor-diagnosed asthma, and 0.6% chronic cough. In the rural population with 3223 participants these figures were 3.3%, 0.7% and 1.2%, respectively. Wheeze was more common in women, cough for 3 months of the year was more common in the age-groups 45+. Those who reported that they currently smoked accounted for 34% in urban and 42% in rural men. Figures were much lower for women (1.5% and 6.0%). Seven out of 574 randomly selected subjects (1.4%) exhibited bronchial hyper-responsiveness to methacholine challenge. Four of 133 (3.0%) people with self-reported wheeze and 3/69 (4.3%) participants with doctor-diagnosed asthma reacted positively on bronchial provocation with methacholine. There was a remarkably high prevalence of positive skin prick tests to aeroallergens: 38% in participants with a history of wheeze and 27% in those without.Conclusion The prevalence of wheeze (particularly in association with bronchial hyper-responsiveness) was low in both rural and urban Gambia. This is in contrast to the relatively high prevalence of positive skin prick tests to aeroallergens (in both wheezers and non-wheezers), questioning the mechanisms of interaction between allergy and asthma and the presence of protective factors against asthma in this West African population. The high smoking rates justify international concern about tobacco marketing in developing societies.

Notes: Background An inverse association between delayed type hypersensitivity to tuberculin and atopy has been observed in children, suggesting that exposure to mycobacteria may influence the immune response to allergens.Objective To investigate the relationship between tuberculin responses and atopy in children living in three different environments in The Gambia.Methods In this cross-sectional study a total of 507 school-aged children were recruited from rural, urban poor or urban affluent communities. They were assessed for skin responses to five common allergens and tuberculin, presence of bacille Calmette–Guérin (BCG) scar, presence of intestinal parasites, and total serum IgE. Atopy was defined as the presence of a skin prick test response ≥ 3 × 3 mm to at least one allergen.Results The overall prevalence of atopy was 33% but there was a significant variation among the three study groups. The prevalence of atopy was 22% in urban poor, 36% in urban affluent, and 43% in rural children. Controlling for potential confounding factors, children in the rural community had a significantly higher odds ratio, 3.3 (95% onfidence interval 1.8–6.0) of being atopic than children from the urban poor community. No association between atopy and tuberculin response or BCG scar was observed in any of the three groups. Serum IgE levels were higher among children of the urban poor group but were not associated with tuberculin response or BCG scar in any of the groups.Conclusion Environmental factors have an important influence on the development of atopy in children in The Gambia but delayed type hypersensitivity to tuberculin is not a protective factor.