Article

Ascaris, atopy, and exercise-induced bronchoconstriction in rural and urban South African children.

National Heart and Lung Institute, Imperial College, London, United Kingdom.
The Journal of allergy and clinical immunology (impact factor: 9.17). 12/2009; 125(1):100-5.e1-5. DOI:10.1016/j.jaci.2009.09.010 pp.100-5.e1-5
Source: PubMed

ABSTRACT Populations with endemic parasitosis have high levels of IgE but low levels of allergic disease. We investigated the association between infection with the parasite Ascaris allergic sensitization, and exercise-induced bronchospasm (EIB).
We sought to investigate the effect of Ascaris infection on bronchial hyperreactivity, skin testing, and specific IgE levels.
A cross-sectional prevalence survey was conducted in urban and rural South African children to measure levels of EIB. A sample of children was enrolled in a nested case-control study for further investigation based on response to exercise. Analyses used weighted logistic regression.
Geometric mean total IgE levels were higher in Ascaris -infected subjects (infected subjects: 451 IU (95% CI, 356-572) vs uninfected subjects: 344 IU (95% CI, 271-437), P = .04), and high levels of total IgE were positively associated with detection of specific IgE to the aeroallergens tested, but there was no significant association between Ascaris infection and titers of specific IgE. Ascaris infection was associated with a decreased risk of a positive skin test response (odds ratio, 0.63; 95% CI, 0.42-0.94; P = .03) but an increased risk of EIB (odds ratio, 1.62; 95% CI, 1.23-2.11; P = .001).
In areas of high parasite endemicity, Ascaris might induce an inflammatory response in the lungs independent of its effect on IgE production. This could explain some of the contradictory findings seen in studies examining the association between geohelminth infection, atopy, and asthma.

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Keywords

Ascaris infection
 
bronchial hyperreactivity
 
cross-sectional prevalence survey
 
endemic parasitosis
 
exercise-induced bronchospasm
 
geohelminth infection
 
low levels
 
lungs independent
 
measure levels
 
nested case-control study
 
parasite Ascaris allergic sensitization
 
parasite endemicity
 
positive skin test response
 
rural South African children
 
skin testing
 
specific IgE
 
specific IgE levels
 
total IgE
 
total IgE levels
 
weighted logistic regression
 

James Calvert