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Keeping Leeches at Bay: Field Evaluation of Plant-Derived Extracts against Terrestrial Blood-Sucking Leeches (Haemadipsidae) in Lao PDR
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
2011 (English)In: Acta Tropica, ISSN 0001-706X, E-ISSN 1873-6254, Vol. 119, no 2-3, 178-182 p.Article in journal (Refereed) Published
Abstract [en]

Terrestrial blood-sucking leeches (Haemadipsidae) are common in the damp forests of the subtropicaland tropical Indo-Pacific region. Members of the genus Haemadipsa are abundant in Laos and adjacentcountries of Southeast Asia, and discomfort to people and livestock. Plant-derived repellents againstarthropods and leeches are common in Lao PDR, and have been used by Lao ethnic groups for generations.Numerous studies have been conducted on the efficacy of traditional plant-derived repellents againstmosquitoes but only a few on repellents against terrestrial blood-sucking leeches. Field experimentswere conducted to evaluate the leech repellent activities of aqueous extracts of three traditionally usedplant species, Sapindus rarak DC., Catunaregam spathulifolia Tirv. and Vernonia elaeagnifolia DC. Stockingsimpregnated with aqueous extracts exhibited moderate to high leech repellent activity, C. spathulifolia(62.6%), V. elaeagnifolia (63.0%), and S. rarak (82.6%). The corresponding repellencies of deltamethrin andDEET were 73.1% and 88.4%, respectively. An aqueous extract of S. rarak applied on cloth at a concentrationof 1.9 mg/cm2 is an effective and practical prevention method significantly reducing the number of bloodfeedingleeches recorded on stockings worn by humans. This plant species is common in Southeast Asiaand can be obtained at limited or no cost.

Place, publisher, year, edition, pages
2011. Vol. 119, no 2-3, 178-182 p.
Keyword [en]
Plant repellents, Leeches, Traditional Knowledge, Parasites
National Category
Microbiology
Identifiers
URN: urn:nbn:se:uu:diva-149973DOI: 10.1016/j.actatropica.2011.05.014ISI: 000293717200018OAI: oai:DiVA.org:uu-149973DiVA: diva2:406107
Available from: 2011-03-24 Created: 2011-03-24 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Botanical Repellents and Pesticides Traditionally Used Against Haematophagous Invertebrates in Lao PDR
Open this publication in new window or tab >>Botanical Repellents and Pesticides Traditionally Used Against Haematophagous Invertebrates in Lao PDR
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Haematophagous parasites and disease vectors such as leeches, ticks, mites, lice, bed bugs, mosquitoes, and myiasis-causing fly larvae are common health problems in Lao Peoples Democratic Republic (Lao PDR). A main aim of my field work in Lao PDR in 2006-2010 was to document traditional knowledge among different ethnic groups about plants that people use to repel or to kill blood-feeding invertebrates. We carried out structured interviews in 66 villages comprising 17 ethnic groups, covering a range of ethnic group, throughout Lao PDR and recorded a total of 92 plant species - in 123 different plant-ectoparasite combinations - that are used as traditional repellents and/or as “pesticides” to kill "pest" invertebrates. Traditional use was confirmed in the scientific literature for 74 of these plant species, and for an additional 13 species based on literature on closely related species. We concluded that repellents and pesticides from many plant species are commonly used in the Lao countryside.

We also investigated traditionally used Lao plants for their activity to repel or to kill certain disease vectors and parasites. Target organisms were mosquitoes (Diptera, Culicidae), fly larvae (Diptera, Cyclorrhapha) in fermented fish production, and terrestrial blood-sucking leeches (Hirudinea, Haemadipsidae). The potential mosquito repellent activities of essential oils of Croton roxburghii (Euphorbiaceae), Hyptis suaveolens (Lamiaceae), and Litsea cubeba (Lauraceae) were evaluated in the field near Vientiane. Oils at concentrations of 1.7-6.7 µg/cm2 were significantly repellent to Aedes, Armigeres and Culex attracted to human baits. The activities against fly larvae, infesting fermenting fish, of three plant species, Tadehagi triquetrum (Fabaceae), Uraria crinita (Fabaceae) and Bambusa multiplex (Poaceae) were investigated: When fresh material of the plants was added on top of fermenting fish infested with fly larvae significant proportions of the larvae were repelled or killed. The total protective effect, i.e., repellent and killing effect combined, of T. triquetrum, U. crinita, and B. multiplex was 60-83 %, 77-90 %, and 60-93 %, respectively.

Field evaluation of the potential leech repellent activities of water extracts of Sapindus rarak (Sapindaceae), Catunaregam spathulifolia (Rubiaceae) and Vernonia elaeagnifolia, (Asteraceae) impregnated on stockings and worn by persons in two leech-infested biotopes revealed leech repellent activities of 82.6%, 62.6% and 63.0%, respectively. The corresponding repellencies of deltamethrin and diethyl-3-methyl-benzamide (DEET) were 73.1% and 88.4%, respectively. Identification of the active components in certain of the plants with the ultimate aim to develop more optimal, less costly repellents, insecticides, acaricides, and anti-leech compounds as alternatives to synthetic repellents and pesticides against blood-feeding insects, ticks, mites, and leeches is in progress.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 825
Keyword
Ethnobotany, fly larvae, Lao PDR, medical entomology, mosquito repellents, myiasis, plant-based insecticides, terrestrial leeches, Haemadipsidae
National Category
Biological Systematics Microbiology
Research subject
Biology with specialization in Systematics
Identifiers
urn:nbn:se:uu:diva-149991 (URN)978-91-554-8075-2 (ISBN)
Public defence
2011-05-19, Zootissalen, Evolutionsmuseet (Museum of Evolution), Villavägen 9, Uppsala, 14:00 (English)
Opponent
Supervisors
Available from: 2011-04-21 Created: 2011-03-24 Last updated: 2011-05-05

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De Boer, Hugo J.

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