Distribution and Seasonal Variation of Phlebotomus and Sergentomyia Sand Fly Populations in Bhutan

Tenzin Wangdi Vector Borne Disease Control Programme, Ministry of Health, Gelephu, Bhutan;

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Sanath Senanayake Department of Parasitology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka;

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Sithar Dorjee Khesar Gyalpo University ofMedical Sciences of Bhutan, Thimphu, Bhutan;

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Tashi Tobgay Khesar Gyalpo University ofMedical Sciences of Bhutan, Thimphu, Bhutan;

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Guofa Zhou Program inPublic Health, University ofCalifornia, Irvine, California

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Sachee B. Piyasiri Department of Parasitology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka;

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W. M. Lakshika I. Weerasinghe Department of Parasitology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka;

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Nadira Karunaweera Department of Parasitology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka;

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Leishmaniasis is considered one of the neglected tropical diseases in the world. Although Bhutan is a member of the visceral leishmaniasis elimination consortium in South Asia, not much attention has been accorded to the disease because of its low incidence. The vector that transmits Leishmania remains poorly understood. In this backdrop, sand-fly surveys were regularly conducted at multiple sites where leishmaniasis cases have been reported in Bhutan. Collections were made using CDC light traps and cattle-baited net traps in 15 villages from February 2019 to May 2022. Six species of Phlebotomus and four species of Sergentomyia were identified from these sites that included two Phlebotomus and three Sergentomyia species discovered for the first time in Bhutan. Sand-fly density varied significantly from village to village, and it showed strong seasonality with peak numbers collected from June to October and almost zero from December to February. Overall, sand-fly density was highest in the basements of the houses and were higher outdoors than indoors. Cattle-baited net traps collected few sand flies during the surveillance period. This work constituted the first systematic sand-fly population surveillance conducted in Bhutan and will provide a baseline for future vector ecology and Leishmania epidemiological studies.

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Author Notes

Financial support: Research reported in this publication was supported by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health under Award Number U01AI136033.

Authors’ addresses: Tenzin Wangdi, Vector Borne Disease Control Programme, Ministry of Health, Gelephu, Bhutan, E-mail: karbay2014@gmail.com. Sanath Senanayake, Sachee B. Piyasiri, W. M. Lakshika I. Weerasinghe, and Nadira Karunaweera, Department of Parasitology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka, E-mails: sanath@parasit.cmb.ac.lk, sacheebhanu@gmail.com, lakshika.iroshani94@gmail.com, and nadira@parasit.cmb.ac.lk. Sithar Dorjee and Tashi Tobgay, Khesar Gyalpo University of Medical Sciences of Bhutan, Thimphu, Bhutan, E-mails: s.dorjee@kgumsb.edu.bt and tobgayla2000@gmail.com. Guofa Zhou, Program in Public Health, University of California, Irvine, CA, E-mail: guofaz@gmail.com.

Address correspondence to Nadira Karunaweera, Department of Parasitology, Faculty of Medicine, University of Colombo, 25 Kynsey Road, Colombo 00800, Sri Lanka. E-mail: nadira@parasit.cmb.ac.lk
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