Risk factors for atopy among school children in a rural area of Latin America.

BACKGROUND: Infection with common childhood infectious diseases including geohelminth infections may provide protection against the development of atopy and allergic disease. Few studies have investigated risk factors for atopy among children living in rural areas of Latin America. OBJECTIVE: To identify risk factors associated with atopy among school-age children in a rural area of Latin America. METHODS: Analytic cross-sectional study of school-age children conducted in seven rural schools in Pichincha Province in Ecuador. Detailed risk factor information was obtained by questionnaire, stool samples were collected for identification of geohelminth parasites, and Mantoux testing was performed to determine tuberculin sensitization. RESULTS: A total of 1002 children from seven rural schools were recruited. The prevalence of geohelminth infections was high (70.1% were infected with at least one geohelminth parasite) and the prevalence of allergic sensitization was high (20.0% had evidence of aeroallergen sensitization). Factors associated with significant protection against atopy in multivariate analyses were the presence of overcrowding in the child's home, low socio-economic level, and infection with geohelminth parasites, and the protective effects of the three factors were statistically independent. CONCLUSION: Low socio-economic level, overcrowding and geohelminth infection, are independently protective against atopy among school-age children living in a rural area of Latin America.

Relationship between bacille Calmette-Guérin vaccination, Mantoux test positivity, and geohelminth infection.

To investigate the potential protective effects of Bacille Calmette-Guerin (BCG) vaccination scar and sensitization to tuberculin against geohelminth infections, we conducted a cross-sectional study among school age children in rural communities in Pichincha Province in Ecuador where BCG vaccination is routinely given at birth. A total of 944 children aged 8-14 years were evaluated for the presence of BCG scars and sensitization to tuberculin, and underwent faecal examination for geohelminth parasites. BCG scars were present in 88.2% of children and positive Mantoux tests were observed in 19.1% of children. Geohelminth prevalence was high with 70.3% infected with any parasite, 52.1% with Ascaris lumbricoides, 52.3% with Trichuris trichiura, 7.6% with Ancylostoma duodenale, and 3.0% with Strongyloides stercoralis. In multivariate analyses, the presence of BCG vaccine scars was not significantly associated with infections with any geohelminth parasite (adjusted odds ratio [AOR] = 0.74, 95% CI 0.43-1.28, P = 0.28), but an inverse association was observed for infections with S. stercoralis that was of borderline statistical significance (AOR = 0.38, 95% CI 0.15-1.00, P = 0.05). There were no associations between sensitization to tuberculin and infection with geohelminth parasites. The data provide little support for an important protective role of neonatal BCG vaccination or current mycobacterial sensitization against geohelminth infections.