Parasitology cambridge.org/par Research Article Cite this article: Al-Mekhlafi HM et al (2019). Prevalence and risk factors of Strongyloides stercoralis infection among Orang Asli schoolchildren: new insights into the epidemiology, transmission and diagnosis of strongyloidiasis in Malaysia. Parasitology 146, 1602–1614. https://doi.org/10.1017/ S0031182019000945 Received: 9 May 2019 Revised: 1 July 2019 Accepted: 1 July 2019 First published online: 31 July 2019 Key words: Malaysia; neglected tropical diseases; Orang Asli; schoolchildren; soil-transmitted helminth; Strongyloides stercoralis Author for correspondence: Hesham M. Al-Mekhlafi, E-mail: halmekhlafi@ yahoo.com and Yvonne A. L. Lim, E-mail: limailian@um.edu.my © Cambridge University Press 2019 Prevalence and risk factors of Strongyloides stercoralis infection among Orang Asli schoolchildren: new insights into the epidemiology, transmission and diagnosis of strongyloidiasis in Malaysia Hesham M. Al-Mekhlafi 1,2 , Nabil A. Nasr 3 , Yvonne A. L. Lim 3 , Fatin Nur Elyana 3 , Hany Sady 4 , Wahib M. Atroosh 3,5 , Salwa Dawaki 6 , Tengku Shahrul Anuar 7,8 , Rahmah Noordin 9 and Rohela Mahmud 3 1 Medical Research Centre, Jazan University, 45142 Jazan, Kingdom of Saudi Arabia; 2 Department of Parasitology, Faculty of Medicine and Health Sciences, Sana’a University, 1247 Sana’a, Yemen; 3 Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia; 4 Department of Medical Laboratories, Faculty of Medical Sciences, Hodeidah University, Hodeidah, Yemen; 5 Department of Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Aden, Aden, Yemen; 6 School of Health Technology, Club Road, Nassarawa, Kano, 700282 Kano State, Nigeria; 7 Centre of Medical Laboratory Technology, Faculty of Health Sciences, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Selangor, Malaysia; 8 Integrative Pharmacogenomics Institute, Universiti Teknologi MARA, Puncak Alam Campus, 42300 Selangor, Malaysia and 9 Institute for Research in Molecular Medicine, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia Abstract This cross-sectional study aimed to determine the prevalence and risk factors of S. stercoralis infection among 1142 Orang Asli primary schoolchildren in six different states of Peninsular Malaysia. Fecal samples were examined using direct smear, formalin-ether sedimentation (FES), agar plate culture (APC) and PCR techniques. Overall, 15.8% of the children were found to be infected with S. stercoralis. The prevalence was 0.2, 1.3, 15.2 and 13.7% by direct smear, FES, APC and PCR, respectively. Multivariate analysis showed that an age of >10 years, being male, belonging to a Proto-Malay tribe, belonging to the Senoi tribe, indiscriminate defecation, using an unimproved water source for drinking water and not wearing shoes when outside were the significant risk factors of infection among these children. In conclu- sion, we provide new evidence on the occurrence of S. stercoralis in Malaysia to show that there is a relatively high prevalence of infection among Orang Asli schoolchildren. Therefore, the use of specific methods for detecting S. stercoralis should be considered when screening these children for intestinal parasites. Moreover, prevention and control mea- sures specific to S. stercoralis should be integrated into the intestinal parasitic infections con- trol programme in Malaysia. Introduction Strongyloidiasis, which is caused by Strongyloides stercoralis, is one of the most difficult-to-diagnose soil-transmitted helminth (STH) infections. It occurs worldwide and is endemic in tropical and temperate climates (Schär et al., 2013; Jourdan et al., 2018). It is con- sidered the most neglected of the neglected tropical diseases and its prevalence is largely underestimated (Olsen et al., 2009; Viney, 2017). Moreover, several aspects of the epidemi- ology of S. stercoralis infection remain poorly documented (Bisoffi et al., 2013; Nutman, 2017). Based on available information; it is estimated that about 370 million people are infected with S. stercoralis worldwide, with the prevalence rate ranging from 10 to 70% in trop- ical and subtropical countries where conducive conditions for transmission such as moist soil and inadequate sanitation coexist. It is particularly evident in underprivileged communities in Latin America, West Africa and Southeast Asia (Schär et al., 2013; Bisoffi et al., 2014; Puthiyakunnon et al., 2014). Humans acquire S. stercoralis infection generally through skin penetration of filariform larvae that exist in contaminated soil. Moreover, donor-derived strongyloidiasis infection in solid organ transplant recipients is increasingly being reported (Kim et al., 2016; Winnicki et al., 2018). Strongyloidiasis is commonly chronic and long lasting with a majority of infected individuals remaining asymptomatic, and infections could be sustained in individuals for more than 75 years (Prendki et al., 2011; Junior et al., 2017). Pulmonary migration of larvae results in transient eosinophilia with cough, dyspnoea (shortness of breath), wheezing and haemoptysis; known as Loeffler’s syndrome which is seen in heavy infections (Al Hadidi et al., 2018). Chronic S. stercor- alis infection may present with fatigue, anorexia, vomiting, abdominal pain, diarrhoea and urti- caria (Khieu et al., 2013; Nutman, 2017). In immunocompetent individuals, infection produces negligible symptoms, but in immunocompromised patients the autoinfection cycle of this parasite https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0031182019000945 Downloaded from https://www.cambridge.org/core. 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