Asthma and lower airway disease
The effect of single and multiple infections on atopy and wheezing in children

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Background

The current epidemic of asthma and atopy has been explained by alterations in immune responses related to reduction in childhood infections. However, the findings of epidemiologic studies investigating the association between infection with atopy and asthma have been inconsistent.

Objective

We sought to investigate the effect of single or multiple infections (pathogen burden) on atopy and wheeze in urban children from Latin America.

Methods

Specific IgE against aeroallergens (sIgE) and skin prick test (SPT) reactivity for the most common local allergens were measured in 1128 children aged 4 to 11 years. Data on wheezing and potential confounders were collected by questionnaire. Infections by 8 pathogens were assessed by using serology and stool examination. Associations of wheeze and atopic outcomes with single and multiple infections were analyzed by means of logistic regression.

Results

Negative results for Toxoplasma gondii were associated with a higher prevalence of sIgE (≥0.70 kU/L), whereas negative results for Ascaris lumbricoides, T gondii, herpes simplex virus, and EBV were associated with a higher prevalence of SPT reactivity. Children with 3 or fewer infection markers had a higher prevalence of sIgE and SPT reactivity compared with those with 4 or more infection markers. However, isolated infections or pathogen burden were not associated with the prevalence of atopic or nonatopic wheeze.

Conclusion

The findings provide support for the idea that the hygiene hypothesis is operating in an urban Latin American context, but its expression is thus far restricted to the atopic status of patients and not the perceived asthma symptoms.

Section snippets

Study population and data collection

The study was conducted in the city of Salvador, Northeastern Brazil, with a population of 2.8 million. The methods of this study have been reported elsewhere.39 Briefly, the entire study population consisted of 1445 children, part of a series of cohorts originally set up to study the effect of a city-wide sanitation program on child health during the period 1996 to 2004.39 The children were resurveyed in 2005 when they were aged 4 to 11 years, and new data were collected, including information

Results

Among 1445 eligible children, the prevalence of current wheezing symptoms was 22.6%, an sIgE level of 0.70 kU/L or greater in serum for at least 1 allergen was present in 37.7%, and a positive SPT response for at least 1 allergen (≥3 mm) was found in 30.3%. The present analysis is based on 1182 of the 1445 eligible children for whom complete data were available. No statistically significant differences were seen in the studied risk factors and outcomes between those children excluded and

Discussion

We investigated the effects of markers of 8 different infections, either individually or aggregated, on the prevalence of atopy (sIgE results) and wheeze and asthma among underprivileged children in an urban center in Latin America. The absence of markers of 4 infections (H simplex, EBV, T gondii, and A lumbricoides) increased the prevalence of positive SPT responses, but only 1 (T gondii) increased the prevalence of positive sIgE levels. None appeared to affect the prevalence of wheezing or

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    • Cited by (0)

    This study was conducted through the Social Change of Asthma and Allergy in Latin America (SCAALA) Programme and funded by the Wellcome Trust (grant no. 072405/Z/03/Z) and by the INCT/MCT/CNPq Programme (contract no. 5737862008-9). CNPq, CAPES, and FAPESB provided scholarships for some of the authors.

    Disclosure of potential conflict of interest: R. L. Fiaccone receives research support from Brazilian National Research Council (CNPq). A. A. Cruz receives research support from the Wellcome Trust, the Brazilian National Research Council (CNPq), and Fundacao de Amparo a Pesquisa da Bahia, Brazil (FAPESB) and is on the Board of Directors for the Global Initiative for Asthma (GINA) and Allergic Rhinitis and its Impact on Asthma. P. J. Cooper receives research support from the Wellcome Trust. The rest of the authors declare that they have no relevant conflicts of interest.

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