Distribution of Giardia duodenalis assemblages A and B among children living in a remote indigenous community of the Northern Territory, Australia.

Amy J Asher,Ross M Andrews,Michelle L Power,Deborah C Holt,Guido Favia

doi:10.1371/journal.pone.0112058

Abstract

Giardiasis is a communicable gastrointestinal disease caused by Giardia duodenalis and two genetic assemblages, A and B, cause human infection. In remote Indigenous communities of Australia, giardiasis is highly prevalent among children but disease transmission is poorly understood. This study investigated the prevalence of Giardia and genetic subtypes contributing to human disease in a remote Indigenous community, in the Northern Territory of Australia. Eighty-seven faecal samples were collected from 74 children (<15 years) over an 18 month period, and the distribution of positive cases relative to participant age and gender were examined. Screening by microscopy and 18S rRNA PCR amplification showed 66.7% (58/87) of faecal samples were positive for Giardia. Both males and females were equally affected and high detection rates were obtained for participants aged 0–<5 years and 5–<10 years (66.0 and 60.0% respectively). For 58.6% of the positive samples, Giardia was only detected by 18S rRNA PCR. Approximately 75% of cases were assemblage B, and subassemblage analyses using terminal restriction fragment length polymorphism of the glutamate dehydrogenase gene demonstrated that a variety of genetic variants were present. The high proportion of positive cases that were not detectable by microscopy, and dominance of assemblage B cases highlights the need for further research in this community, to assess the contribution of Giardia to chronic gastrointestinal disease among children, and to understand conditions conductive to assemblage B transmission.

Highlights

In Australia, the mortality rates for Indigenous children (0–14 years) are more than two times higher than the rates for nonIndigenous children, and overall life expectancy of Indigenous Australians remains 9.7–11.5 years below the non-Indigenous population [1]
Microscopy and DNA extraction To investigate the prevalence of G. duodenalis, we examined 87 faecal samples that were collected as part of a mass drug administration trial of ivermectin for the control of scabies and strongyloidiasis in a remote community in the Northern Territory [18]
Comparison of results showed that of the 58 positive samples, 20/58 (34.5%) were positive by both screening methods, 34/58 (58.6%) were positive by 18S rRNA PCR only, and 4/58 (6.9%) samples were positive by microscopy only

Summary

Introduction

In Australia, the mortality rates for Indigenous children (0–14 years) are more than two times higher than the rates for nonIndigenous children, and overall life expectancy of Indigenous Australians remains 9.7–11.5 years below the non-Indigenous population [1]. In remote Indigenous communities, high rates of gastrointestinal, respiratory, and skin infections are common and children are most at risk from constant infection and re-infection [2]. A protozoan parasite, is a significant cause of gastrointestinal disease (giardiasis) and morbidity [4]. In remote Indigenous communities giardiasis prevalence is high, ranging from 15 to 36% [4,5], compared to a national prevalence of 2 to 7% [6]. Among Indigenous children living in remote communities, prevalence of giardiasis is estimated between 32 to 65% and frequency of transmission is comparable to rates observed in developing nations [4,7,8]. Constant exposure to Giardia leads to chronic gastrointestinal disease, malnutrition, and failure to thrive [9]

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