Endotoxin, Ergosterol, Fungal DNA and Allergens in Dust from Schools in Johor Bahru, Malaysia- Associations with Asthma and Respiratory Infections in Pupils

Dan Norbäck,Lennart Larsson,Yi-Wu Zheng,Pawel Markowicz,Gui-Hong Cai,Xu-Xin Lai,Michael Dho Spangfort,Faridah Ali,Jamal Hisham Hashim,Zailina Hashim

doi:10.1371/journal.pone.0088303

Abstract

There are few studies on associations between respiratory health and allergens, fungal and bacterial compounds in schools in tropical countries. The aim was to study associations between respiratory symptoms in pupils and ethnicity, chemical microbial markers, allergens and fungal DNA in settled dust in schools in Malaysia. Totally 462 pupils (96%) from 8 randomly selected secondary schools in Johor Bahru, Malaysia, participated. Dust was vacuumed from 32 classrooms and analysed for levels of different types of endotoxin as 3-hydroxy fatty acids (3-OH), muramic acid, ergosterol, allergens and five fungal DNA sequences. Multiple logistic regression was applied. Totally 13.1% pupils reported doctor’s diagnosed asthma, 10.3% wheeze and 21.1% pollen or pet allergy. Indian and Chinese children had less atopy and asthma than Malay. Carbon dioxide levels were low (380–690 ppm). No cat (Fel d1), dog (Can f 1) or horse allergens (Ecu cx) were detected. The levels of Bloomia tropicalis (Blo t), house dust mite allergens (Der p 1, Der f 1, Der m 1) and cockroach allergens (Per a 1 and Bla g 1) were low. There were positive associations between levels of Aspergillus versicolor DNA and daytime breathlessness, between C14 3-OH and respiratory infections and between ergosterol and doctors diagnosed asthma. There were negative (protective) associations between levels of C10 3-OH and wheeze, between C16 3-OH and day time and night time breathlessness, between cockroach allergens and doctors diagnosed asthma. Moreover there were negative associations between amount of fine dust, total endotoxin (LPS) and respiratory infections. In conclusion, endotoxin at school seems to be mainly protective for respiratory illness but different types of endotoxin could have different effects. Fungal contamination measured as ergosterol and Aspergillus versicolor DNA can be risk factors for respiratory illness. The ethnical differences for atopy and asthma deserve further attention.

Highlights

The large ISAAC international study has shown that the increase of asthma is most pronounced in middle-income countries, especially in Asia Pacific [1]
Fungal DNA from Aspergillus versicolor was positively associated while fungal DNA from Stachybotrys sp. was negatively associated with daytime attacks of breathlessness
Endotoxin at school seems to be mainly protective for respiratory illness but different types of endotoxin seemed to have different effects C10 3-hydroxy fatty acids (3OH FA) and C16 3-OH FA were protective while C14 3-OH FA was a risk factor for respiratory illness

Summary

Introduction

The large ISAAC international study has shown that the increase of asthma is most pronounced in middle-income countries, especially in Asia Pacific [1]. In Malaysia, a tropical country, previous studies from 1990 to 2001 have found 3–10% asthma and 5–8% wheeze prevalence among school children, with a trend towards an increase of asthma in the 1990s [2,3,4]. We found no later studies on asthma or allergy in Malaysian school children. A recent review concluded that schools might be important sources of allergen exposures, including cat and dog allergens [7]. Most school environment studies are from industrialized countries in temperate climate zones [5,6,7]

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