Durham Research Online Deposited in DRO: 24 March 2021 Version of attached le: Accepted Version Peer-review status of attached le: Peer-reviewed Citation for published item: Tangena, Julie-Anne A and Thammavong, Phoutmany and Malaithong, Naritsara and Inthavong, Thavone and Ouanesamon, Phuthasone and Brey, Paul T and Lindsay, Steve W (2017) 'Diversity of Mosquitoes (Diptera: Culicidae) Attracted to Human Subjects in Rubber Plantations, Secondary Forests, and Villages in Luang Prabang Province, Northern Lao PDR.', Journal of medical entomology., 54 (6). pp. 1589-1604. 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Durham University Library, Stockton Road, Durham DH1 3LY, United Kingdom Tel : +44 (0)191 334 3042 | Fax : +44 (0)191 334 2971 https://dro.dur.ac.uk Journal of Medical Entomology, 2017, 1–16 doi: 10.1093/jme/tjx071 Sampling, Distribution, Dispersal Research article Diversity of Mosquitoes (Diptera: Culicidae) Attracted to Human Subjects in Rubber Plantations, Secondary Forests, and Villages in Luang Prabang Province, Northern Lao PDR Julie-Anne A. Tangena,1,2,3 Phoutmany Thammavong,1 Naritsara Malaithong,4 Thavone Inthavong,5 Phuthasone Ouanesamon,5 Paul T. Brey,1,* and Steve W. Lindsay2* 1Department of Medical Entomology, Institut Pasteur du Laos, Samsenthai Rd, Ban Kao-gnot, PO Box 3560, Vientiane, Lao PDR ([email protected]; [email protected]; [email protected]), 2School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, United Kingdom ([email protected]), 3Corresponding author, e-mail: [email protected], 4Department of Entomology, Kasetsart University, 50 Ngam Wong Wan Rd., Ladyaow Chatuchak Bangkok 10900, Thailand ([email protected]), and 5Agriculture and Forestry Policy Research Center, National Agriculture and Forestry Research Institute, Nongviengkham Village, Vientiane, P.O Box 7170, Lao PDR ([email protected]; [email protected]) *Joint senior authors. Subject Editor: Richard Wilkerson Received 22 December 2016; Editorial decision 4 March 2017 Abstract The impact of the rapid expansion of rubber plantations in South-East Asia on mosquito populations is uncer- tain. We compared the abundance and diversity of adult mosquitoes using human-baited traps in four typical rural habitats in northern Lao PDR: secondary forests, immature rubber plantations, mature rubber plantations, and villages. Generalized estimating equations were used to explore differences in mosquito abundance be- tween habitats, and Simpson’s diversity index was used to measure species diversity. Over nine months, 24,927 female mosquitoes were collected, including 51 species newly recorded in Lao PDR. A list of the 114 mosquito species identified is included. More mosquitoes, including vector species, were collected in the sec- ondary forest than immature rubber plantations (rainy season, odds ratio [OR] 0.33, 95% confidence interval [CI] 0.31–0.36; dry season, 0.46, 95% CI 0.41–0.51), mature rubber plantations (rainy season, OR 0.25, 95% CI 0.23–0.27; dry season, OR 0.25, 95% CI 0.22–0.28), and villages (rainy season, OR 0.13, 95% CI 0.12–0.14; dry sea- son, 0.20, 95% CI 0.18–0.23). All habitats showed high species diversity (Simpson’s indexes between 0.82–0.86) with vectors of dengue, Japanese encephalitis (JE), lymphatic filariasis, and malaria. In the secondary forests and rubber plantations, Aedes albopictus (Skuse), a dengue vector, was the dominant mosquito species, while in the villages, Culex vishnui (Theobald), a JE vector, was most common. This study has increased the overall knowledge of mosquito fauna in Lao PDR. The high abundance of Ae. albopictus in natural and man-made for- ests warrants concern, with vector control measures currently only implemented in cities and villages. Key words: mosquito population dynamics, mosquito fauna, rubber plantation, Lao People’s Democratic Republic South-East Asia (SEA) is a region where the population is at high risk The largest rubber plantations in the world are located in Indonesia, of exposure to vector-borne diseases (Jones et al. 2008, Suwonkerd Thailand, and Malaysia. Together with other rubber-producing coun- et al. 2013). This risk is exacerbated by changes in the environment, tries in SEA, they covered 9.2 million ha of land in 2010 (Food and such as changes in land use, surface water availability, large-scale Agriculture Organization 2010). These man-made forests provide en- cross-border migration of people, and climate change (Githeko et al. vironments for vector mosquitoes. Outbreaks of dengue (Ministry of 2000, Foley et al. 2005, Reisen 2010, Parham et al. 2015). One major Health Malaysia 2013, Palaniyandi 2014), malaria (Watson 1921, land-use change in the region is the expansion of rubber plantations. Singhasivanon et al. 1999, Garros et al. 2008, Wangroongsarb et al. VC The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: [email protected] 1 2 Journal of Medical Entomology, 2017, Vol. 0, No. 0 2012, Bhumiratana et al. 2013b), and chikungunya (Kumar et al. secondary forests are forests that had re-grown after the primary 2011, Palaniyandi 2014) have been recorded in rubber plantations of forests had been cut for timber. There are few mature trees with India, Myanmar, Thailand, and Viet Nam. However, data on the bamboo shrubs and small trees dominating. Immature plantations abundance and diversity of mosquitoes in rubber plantations remain are those with rubber trees less than five years old, which had not limited (Tangena et al. 2016). been tapped for latex. These immature plantations have little canopy Lao PDR (People’s Democratic Republic) has one of the fastest cover and a high density of undergrowth. Mature rubber plantations growing economies in SEA, with a 6.4% increase in gross domestic are where the trees were more than five years old and over 70% of product (GDP) in 2015 (The World bank 2015). This growth has the trees had been tapped for latex for at least one year. As the trees partly been achieved by the 160-fold expansion of mature rubber are accessed regularly, the plantations had little undergrowth. The plantations from 2010 to 2015. Rubber tree cultivation is a new villages were linear rural settlements with 700–1,000 inhabitants. kind of mass farming, and the impact of these changes on local vec- Generally, villagers lived either in one-storey bamboo houses with tors remains poorly understood (Rueda et al. 2015). Since rubber thatched roofs or brick houses with metal roofs. Aquatic habitats plantations are likely to expand in the country for at least the next near the trapping sites were investigated for the immature rubber decade (National Agriculture and Forestry Research Institute 2016), plantations, mature rubber plantations, and villages (Tangena et al. there is a need to understand the risk of vector-borne diseases in 2016). The greatest number of waterbodies positive for immature these habitats. mosquito stages were found in the mature rubber plantations. The The objective of this study was to identify the mosquito dynam- most important waterbodies were latex collection cups, tyres, and ics, specifically for vectors of human diseases in rural habitats com- water container > 10 liters. In the villages, the second greatest num- mon in Lao PDR. A longitudinal study was carried out in northern ber of waterbodies positive for mosquitoes were found. Mainly wa- Lao PDR to determine the abundance and diversity of adult mosqui- ter containers > 10 liters and cut bamboo were positive for toes in four typical rural habitats: secondary forests, immature rub- immature mosquitoes. In the immature rubber plantations, the low- ber plantations, mature rubber plantations, and villages. We est number of waterbodies were found. Larvae and pupae were hypothesized that mature rubber plantations in Lao PDR, with simi- found in leaf axils and cut bamboo. larly high canopy cover, high humidity, and stable temperatures as forest habitats, would provide a good alternative habitat for forest mosquitoes, including important dengue and malaria vectors. Longitudinal Mosquito Collections Adult blood-questing female mosquitoes were sampled using the human-baited double net (HDN) trap (Tangena et al. 2015). Briefly, Materials and Methods the HDN trap consisted of one participant resting on a bamboo bed covered by two untreated bed nets: the smaller one completely sur- Study Design rounded the human subject, while the larger one was positioned Entomological surveys were conducted monthly from July to over the smaller net and raised off the ground to let mosquitoes be November 2013 and in February, March, May, and July of 2014. caught between the two nets. Every hour for 10 min the participant Collections were not conducted in December 2013, January 2014, raised the bottom of the inner net and aspirated all mosquitoes April 2014, and June 2014 due to national holidays, local festivals, caught between the two bed nets into labelled paper-cups. peak in rice planting activities, and a large temporary migration of Specimens were frozen at À20C and morphologically identified to villagers. Temperature and humidity data were collected in all habi- species or species complex using Thai identification keys tats throughout the study period, with the additional environmental (Rattanarithikul et al.