Date Published: February 27, 2007
Publisher: Public Library of Science
Author(s): Matthias Wjst, Daniel Boakye
Abstract: A new survey shows a recent increase in the prevalence of asthma and allergic diseases in children in Ghana. Wjst and Boakye put this survey into context through a discussion of the epidemiology of asthma in Africa.
Partial Text: Whatever does not exist does not have a name (African proverb).
Looking at about 120 papers from Medline on asthma in Africa, we found that asthma research is currently dominated by authors from South Africa, followed by authors from Nigeria, Tanzania, Ethiopia, Kenya, and The Gambia. Most are case studies, closely followed by cross-sectional studies, and then case-control studies. There have been very few cohort studies. Only a few studies use objective measures [2,3], which makes the new PLoS Medicine study unusual, since the researchers used repeated measurements of skin prick tests and bronchial reactivity .
The clinical presentation of asthma in Africa does not seem to be different from other parts of the world , although one study reports later disease onset in Africa . Assumed risk factors are local flora such as Kikuyu grass, Makaore cherry, Tanganyika aningré, and Der néré as well as helminthic infection by Trichuris, Schistosoma, Ascaris, and hookworm (Figure 1). Well-known allergens in Africa are house dust mite, cockroach, and cat and dog dander; a less well known allergen is washing soap. Parental history, female sex, low physical activity, and malnutrition, have been described as risk factors together with pesticides, insecticides, wood or kerosene heating, grass mats, mud and cow dung, smoking, and car and truck diesel exhaust. In the occupational setting isocyanate and latex sensitivity have been reported as risk factors, and poultry workers, hairdressers, gold miners, and wood choppers are reported as having an increased risk of asthma. Annual rainfall seems to have an influence on symptom presentation.
Intercountry prevalence data are limited to the International Study of Asthma and Allergies in Childhood (ISAAC, http://isaac.auckland.ac.nz) in which seven African countries participated (English-speaking regions: Ethiopia 9.1%, Kenya 15.8%, Nigeria 13.0%, and South Africa 20.3%; and French-speaking regions: Algeria 8.7%, Morocco 10.4%, and Tunisia 11.9% ). Symptom rates are lower than in industrialized countries, while only South Africa approaches rates found in the UK. The interpretation of these figures, however, is difficult; there might be an increase with gross domestic product and industrialization factors . Rural African regions always showed much lower asthma prevalence rates than urban areas . People living in rural grasslands rarely, if ever, suffer from allergic diseases and some do not even have a term to describe this condition .
As in industrialized countries asthma in Africa is determined by genes and environment. However, both genetic and environmental effects may operate in different directions and on different scales.
Given the large African continent, its enormous health problems, and its poverty, there needs to be a shift in donor countries’ funding priorities . We believe that this shift might be even in the interest of the developed countries that are now suffering from high rates of asthma , since major characteristics of traditional lifestyle have changed irrespective of socioeconomic status. Many African societies are still going through the early stages of the transition to urbanised economies, leaving us all opportunities to look for the factors driving early sensitisation and later asthma . In that respect Africa probably has more to offer than any study in the developed world.