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House-dust mite species in Bloemfontein, South Africa
Werner Sinclair1, Louise Coetzee, Gina Joubert
1University of the Free State. sinclaiw@fshealth.gov.za
Unlabelled:
House-dust mites (HDMs) are an important source of allergens that are reputed to act as a trigger for atopic disease. Climatic conditions in parts of South Africa are not suitable for their proliferation, and there is doubt whether they occur on the Highveld. We studied whether HDMs occur in homes in Bloemfontein, Free State.
Methods:
Ten houses were sampled over a 1-year period. Dust was collected monthly or quarterly from a mattress, a bedroom floor and the living room floor of each house and examined for the presence of HDMs. Climate data were collected during the same period and a questionnaire was completed by home-owners to gather data on indoor factors that could influence mite proliferation.
Results:
HDMs were regularly found in 3 houses (30%). Dermatophagoides farinae was the dominant species (97.5%). The highest numbers were found in winter, when climatic conditions were the least favourable. Climatic conditions never met the requirements for active proliferation of the mites. Indoor factors that may have promoted mite proliferation in some houses were artificial heating (especially under-floor heating), en-suite bathrooms and lack of adequate ventilation during the winter months.
Conclusion:
HDMs do occur in central South Africa, owing to a microclimate created indoors. Adequate ventilation, to reduce indoor humidity, should suffice to reduce mite numbers and prevent atopic symptoms induced by them.
Insights
House-dust mites (HDMs) are present in homes in central South Africa, despite unfavorable outdoor climates. Indoor conditions like heating and poor ventilation contribute to their proliferation, suggesting ventilation as a key control method.
Area of Science:
- Allergen research
- Environmental health
- South African climate studies
Background:
- House-dust mites (HDMs) are significant allergens linked to atopic diseases.
- Previous assumptions questioned the presence of HDMs in South Africa's Highveld due to climate.
- This study investigated HDM occurrence in Bloemfontein, Free State.
Purpose of the Study:
- To determine the presence and prevalence of house-dust mites (HDMs) in homes on the Highveld of South Africa.
- To identify factors influencing HDM occurrence in Bloemfontein residences.
- To inform strategies for managing HDM-related allergies in the region.
Main Methods:
- Dust samples collected monthly/quarterly over one year from mattresses and floors in ten houses.
- Examination of dust for the presence of HDMs.
- Collection of climate data and homeowner questionnaires on indoor environmental factors.
Main Results:
- HDMs were detected in 30% of sampled houses, with Dermatophagoides farinae being dominant.
- Mite numbers peaked in winter, despite unfavorable external climatic conditions for proliferation.
- Indoor factors such as artificial heating and inadequate ventilation correlated with higher mite presence.
Conclusions:
- House-dust mites (HDMs) successfully inhabit central South African homes by creating indoor microclimates.
- Improving indoor ventilation to reduce humidity is recommended to control HDM populations.
- Reducing HDM exposure through ventilation may help prevent associated atopic symptoms.