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IgE response to Ascaris lumbricoides in Russian children indicates IgE responses to common environmental allergens

The ultimate causes for geographic variation in atopy prevalence remain unknown. There is evidence of cross reactivity between Ascaris lumbricoides and inhalant and food allergens (1). Intestinal parasites have been proposed to reduce the risk of atopy especially in low socioeconomic status environments (2). The prevalence of atopy is significantly lower in Russian compared to Finnish Karelia, but the reasons for this contrast are largely unidentified (3). Our aim was to explore whether A. lumbricoides, which still is quite prevalent in Russian Karelia but virtually non-existent in Finland, has an effect on the expression of atopy. The population survey in Russian and Finnish Karelia was carried out in 2003. The study areas and methods have been described in detail elsewhere (3, 4). The study was based on a random sample of 6–16 year old school children and their mothers. In Russia, 550 child– mother pairs were enrolled in the survey. Data was obtained using questionnaires, skin prick tests (SPT) and IgE measurements. For the purpose of this study, we analyzed 419 children and their 315 mothers who had SPT and measurements of allergen-specific as well as Ascaris-specific IgE. For SPT, a wheal diameter of 3 mm or larger, and for IgE measurements, concentrations of 0.35 IU/ml or greater were defined as positive. Out of the 419 children and 315 mothers, 88 (21%) and 56 (17.9%) showed Ascaris-specific IgE, respectively. The prevalence of at least one positive IgE response to common allergens was higher in Ascaris-IgE positive vs. Ascaris-IgE negative children (Table 1). The unadjusted odds ratio for Ascaris-IgE positive children to have a positive IgE for one more common allergen was 4.023 (95% CI; 2.423–6.679). The difference in SPT results was not significantly different in Ascaris-IgE positive and negative children. For mothers the differences in IgE responses or SPT to common allergens were not different between Ascaris negative and positive groups. The IgE response to Ascaris was associated with IgE responses to common allergens in children living in Russian Karelia, where A. lumbricoides infection is still quite prevalent. However, Ascaris IgE is not specific for ongoing Ascaris infection because other helminths affect it as well (5). The intensity of the helminth infection has been reported to affect the risk of atopic sensitization and clinical symptoms. The Ascaris specific IgE values for Russian children and mothers ranged from 0 to 19.8 and 0–30.8 IU/ml, respectively. Mild Ascaris infections have been reported to increase allergic reactivity whereas severe infections might be suppressive (5). The attenuating effect of Ascaris on atopy has been reported in areas where helminth infections are endemic and the exacerbating effect from areas where Ascaris is not that common (6). In Russian Karelia Ascaris is not endemic and its prevalence is much lower than in some tropical areas. Continuous, and especially early childhood exposure, to Ascaris infection among Russian children enhances sensitization to common allergens and does not confer protection against atopy. ALLERGY Net