Patterns of Allergic Sensitization and Factors Associated With Emergence of Sensitization in the Rural Tropics Early in the Life Course: Findings of an Ecuadorian Birth Cohort

Abstract

Introduction: There are limited data on emergence of allergic sensitization (or atopy) during childhood in tropical regions.Methods: We followed a birth cohort of 2,404 newborns to 8 years in tropical Ecuador and collected: risk factor data by maternal questionnaires periodically from birth; atopy was measured by skin prick test reactivity (SPT) to aeroallergens in parents, and aeroallergens and food allergens in children at 2, 3, 5, and 8 years; and stool samples for soil-transmitted helminths (STH) from children periodically to 8 years and from parents and household members at the time of recruitment of cohort children. Data on risk factors were measured either at birth or repeatedly (time-varying) from birth to 8 years. Longitudinal repeated-measures analyses were done using generalized estimating equations to estimate the age-dependent risk of positive SPT (SPT+) to any allergen or mite during early childhood.Results: SPT+ to any allergen was present in 29.0% of fathers and 24.8% of mothers, and in cohort children increased with age, initially to mite but later to cockroach, reaching 14.8% to any allergen (10.7% mite and 5.3% cockroach) at 8 years. Maternal SPT+, particularly presence of polysensitization (OR 2.04, 95% CI 1.49–2.77) significantly increased the risk of SPT+ during childhood, while household overcrowding at birth decreased the risk (OR 0.84, 95% CI 0.72–0.98). For mite sensitization, maternal polysensitization increased (OR 2.14, 95% CI 1.40–3.27) but rural residence (OR 0.69, 95% CI 0.50–0.94) and birth order (3rd−4th vs. 1st−2nd: OR 0.71, 95% CI 0.52–0.98) decreased the risk. Time-varying exposures to agricultural activities (OR 0.77, 95% CI 0.60–0.98) and STH parasites (OR 0.70, 95% CI 0.64–0.91) during childhood decreased while anthelmintics increased the childhood risk (OR 1.47, 95% CI 1.05–2.05) of mite sensitization.Conclusion: Our data show the emergence of allergic sensitization, primarily to mite and cockroach allergens, during childhood in tropical Ecuador. A role for both antenatal and post-natal factors acting as potential determinants of SPT+ emergence was observed.

Allergic diseases in India – Prevalence, risk factors and current challenges

“…59 Aeroallergen sensitization rates among children from other LMIC's range from 8.7% in Ethiopia, to 25% in Uganda. 60 In SAFFA, food sensitization and allergy were higher in urban (9.0%, 2.3%) than rural areas (2.8%, 0.5%). Very low food sensitization rates were observed in Uganda (<1.5%), Ecuador (0.5%) and Indonesia (0.8%).…”

“…Very low food sensitization rates were observed in Uganda (<1.5%), Ecuador (0.5%) and Indonesia (0.8%). 60 The differences between sensitization rates to foods and food allergy in other LMICs are not as stark as that reported by the Indian population.…”

“…An interesting aspect of this study was the observation that children with poorer nutritional status had less sensitization 59 . Aeroallergen sensitization rates among children from other LMIC's range from 8.7% in Ethiopia, to 25% in Uganda 60 . In SAFFA, food sensitization and allergy were higher in urban (9.0%, 2.3%) than rural areas (2.8%, 0.5%).…”

Effect of infant viral respiratory disease on childhood asthma in a non‐industrialized setting

“…Allergen skin prick testing (SPT) was performed at 2 years for a panel of nine allergens (house dust mites, cockroach, dog, cat, fungi, grass pollens, egg, milk, and peanut) as described. 25 A positive test was a mean wheal diameter ≥2 mm greater than the negative saline control. SPT positivity was defined as reactivity to any allergen.…”

Effects of Aeroallergen Sensitization on Symptom Severity, Pulmonary Function, and Bronchodilator Response in Children With Bronchial Asthma

“…[2] Atopic sensitization or allergen sensitization can be measured either in vivo by the presence of IgEmediated inflammation to allergen extracts (skin prick test) or in vitro by allergen-specific IgE levels (blood sample) to identify whether the patient is monosensitized (sensitized to one allergen) or polysensitized (sensitized to ≥2 allergens). [3] Among all the commonly used markers of sensitization, skin prick test (SPT) correlated best with the level of lung function among symptomatic subjects. [4] The question on how allergic sensitization and its patterns influence the development and severity of asthma, as well as its effect in pulmonary function were subjects of interest in scientific studies.…”