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Tokelau: a unique low allergen environment at sea level
1Wellington Asthma Research Group, Wellington School of Medicine and Health Sciences, Wellington, New Zealand.
Summary
Tokelau children have lower asthma and atopy rates, linked to significantly lower indoor dust mite allergen levels in their homes. This contrasts with higher allergen exposure in New Zealand, explaining the observed health differences.
Area of Science:
- Environmental Health
- Allergy and Immunology
- Epidemiology
Background:
- Children in Tokelau exhibit lower asthma and atopy prevalence than Tokelauan children residing in New Zealand.
- A hypothesis suggests that reduced indoor allergen exposure in Tokelau contributes to the lower prevalence of asthma and atopy.
Purpose of the Study:
- To investigate the association between indoor allergen levels and the prevalence of asthma and atopy in Tokelau.
- To compare indoor allergen levels (dust mites, endotoxin) in homes in Tokelau and New Zealand.
Main Methods:
- Dust samples were collected from 76 homes and four public buildings in Tokelau, and 30 homes of Tokelauan families in New Zealand.
- Samples were analyzed for specific allergens including Der p 1, Der f 1, Can f 1, Fel d 1, Bla g 2, and Blo t 5 using ELISA.
- Endotoxin levels were quantified using a kinetic amoebocyte lysate assay.
Main Results:
- Der p 1 levels were over 1000-fold lower in Tokelau (geometric mean 0.04 microg/g) compared to New Zealand (47.0 microg/g in beds, 44.7 microg/g on floors).
- Can f 1 and Fel d 1 levels were also significantly lower in Tokelau.
- Bed endotoxin levels were substantially higher in Tokelau (26,736 EU/g) versus New Zealand (5,181 EU/g), while floor endotoxin levels were similar.
Conclusions:
- The significantly lower indoor allergen levels in Tokelauan homes, particularly for dust mite allergens, provide a strong explanation for the reduced prevalence of asthma and atopy.
- Higher endotoxin levels in Tokelauan beds did not correlate with increased asthma/atopy, suggesting mite allergens are the primary drivers of the observed differences.