Detection of Schistosoma mekongi DNA in Human Stool and Intermediate Host Snail Neotricula aperta via Loop-Mediated Isothermal Amplification Assay in Lao PDR

Takashi Kumagai; Emilie Louise Akiko Matsumoto-Takahashi; Hirofumi Ishikawa; Sengdeuane Keomalaphet; Phonepadith Khattignavong; Pheovaly Soundala; Bouasy Hongvanthong; Kei Oyoshi; Yoshinobu Sasaki; Yousei Mizukami; Shigeyuki Kano; Paul T Brey; Moritoshi Iwagami

doi:10.3390/pathogens11121413

Detection of Schistosoma mekongi DNA in Human Stool and Intermediate Host Snail Neotricula aperta via Loop-Mediated Isothermal Amplification Assay in Lao PDR

Pathogens. 2022 Nov 24;11(12):1413. doi: 10.3390/pathogens11121413.

Authors

Takashi Kumagai¹, Emilie Louise Akiko Matsumoto-Takahashi^{2

3}, Hirofumi Ishikawa¹, Sengdeuane Keomalaphet⁴, Phonepadith Khattignavong⁴, Pheovaly Soundala⁴, Bouasy Hongvanthong⁵, Kei Oyoshi⁶, Yoshinobu Sasaki⁶, Yousei Mizukami⁶, Shigeyuki Kano^{2

4}, Paul T Brey⁴, Moritoshi Iwagami^{2

4}

Affiliations

¹ Department of Parasitology and Tropical Medicine, Tokyo Medical and Dental University, Tokyo 113-8510, Japan.
² Research Institute, National Center for Global Health and Medicine, Tokyo 162-8655, Japan.
³ Graduate School of Public Health, St. Luke's International University, Tokyo 104-0044, Japan.
⁴ Institut Pasteur du Laos, Ministry of Health, Vientiane P.O. Box 3560, Laos.
⁵ Center of Malariology, Parasitology and Entomology, Ministry of Health, Vientiane P.O. Box 0100, Laos.
⁶ Earth Observation Research Center, Japan Aerospace Exploration Agency (JAEA), Tsukuba 305-8505, Japan.

Abstract

Schistosomiasis mekongi infection represents a public health concern in Laos and Cambodia. While both countries have made significant progress in disease control over the past few decades, eradication has not yet been achieved. Recently, several studies reported the application of loop-mediated isothermal amplification (LAMP) for detecting Schistosoma DNA in low-transmission settings. The objective of this study was to develop a LAMP assay for Schistosoma mekongi using a simple DNA extraction method. In particular, we evaluated the utility of the LAMP assay for detecting S. mekongi DNA in human stool and snail samples in endemic areas in Laos. We then used the LAMP assay results to develop a risk map for monitoring schistosomiasis mekongi and preventing epidemics. A total of 272 stool samples were collected from villagers on Khon Island in the southern part of Laos in 2016. DNA for LAMP assays was extracted via the hot-alkaline method. Following the Kato-Katz method, we determined that 0.4% (1/272) of the stool samples were positive for S. mekongi eggs, as opposed to 2.9% (8/272) for S. mekongi DNA based on the LAMP assays. Snail samples (n = 11,762) were annually collected along the riverside of Khon Island from 2016 to 2018. DNA was extracted from pooled snails as per the hot-alkaline method. The LAMP assay indicated that the prevalence of S. mekongi in snails was 0.26% in 2016, 0.08% in 2017, and less than 0.03% in 2018. Based on the LAMP assay results, a risk map for schistosomiasis with kernel density estimation was created, and the distribution of positive individuals and snails was consistent. In a subsequent survey of residents, schistosomiasis prevalence among villagers with latrines at home was lower than that among villagers without latrines. This is the first study to develop and evaluate a LAMP assay for S. mekongi detection in stools and snails. Our findings indicate that the LAMP assay is an effective method for monitoring pathogen prevalence and creating risk maps for schistosomiasis.

Keywords: LAMP; Laos; Schistosoma mekongi; risk map.

Abstract

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