Children with gastrointestinal helminthiasis — particularly Trichiuris trichura — are more likely to have asthma, according to findings of a study of children in Sri Lanka that was published in the International Journal of Infectious Diseases.
Sri Lanka has an increasing prevalence of childhood asthma and is currently transitioning from a high to low burden of helminthiasis (ie, worm infestation). To investigate the association between helminthiasis and childhood asthma, researchers in Sri Lanka conducted a case-controlled population-based cohort study of data on 380 children (6-14 years of age) who took part in a larger study of sleep-related and respiratory diseases.
Stool samples were taken from cohorts of 190 children with asthma and 190 children without asthma randomly selected from the larger study population. The association between gastrointestinal helminth species and asthma was evaluated with logistic regression models. Parental responses were used to validate asthma status based on the International Study of Asthma and Allergies in Childhood questionnaire. Children with immunocompromising systemic treatment, severe physical disability, and severe mental disability were excluded. Children with asthma in this sample were more likely to be male and have mothers with a higher level of education than the children in the cohort without asthma.
Using a case-control study nested in a cohort study of children, we found that Trichiuris trichura infestation is strongly associated with current asthma but that other gastrointestinal helminthiasis or the helminth load are not associated with asthma.
Investigators found helminthiasis in 23.3% (n=44) of the children with asthma and in 15.3% (n=23) of the children without asthma. Moreover, children with asthma were more likely to have helminthiasis (adjusted odds ratio [aOR], 3.7; 95% CI, 1.7-7.7; P =.001) and were especially more likely to be infested with Trichiuris trichura (aOR, 4.5; 95% CI, 1.6-12.3; P =.004). Asthma was not associated with other helminths or the total or species-specific intensity of infestation measured by eggs per gram (P <.05).
Co-infestations by more than 1 gastrointestinal helminth were found in 3 children. Intensity of infestations was considered low.
Study limitations include limited data collection, unmeasured variables, the use of a floatation technique and microscopic analysis on a single stool sample to detect helminths, misclassifications of eggs and larvae, reliance on parental-reported asthma instead of clinical validations, and a lack of clinical measurements of peripheral blood eosinophils, sputum, or immunoglobulin E levels.
“Using a case-control study nested in a cohort study of children, we found that Trichiuris trichura infestation is strongly associated with current asthma but that other gastrointestinal helminthiasis or the helminth load are not associated with asthma,” investigators concluded. “Given that 1.5 billion people amounting to 24% of the global population are affected by helminthiasis which can be significantly reduced by low-cost interventions, resolution of this association to inform policy and population-based interventions to mitigate the burden of asthma has immense health and financial benefits.”