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Botanical Repellents and Pesticides Traditionally Used Against Haematophagous Invertebrates in Lao PDR
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology. (Medical Entomology)
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 [en]
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: urn:nbn:se:uu:diva-149991ISBN: 978-91-554-8075-2OAI: oai:DiVA.org:uu-149991DiVA: diva2:406136
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
List of papers
1. Botanical Repellents and Pesticides Traditionally Used Against Hematophagous Invertebrates in Lao People's Democratic Republic: A Comparative Study of Plants Used in 66 Villages
Open this publication in new window or tab >>Botanical Repellents and Pesticides Traditionally Used Against Hematophagous Invertebrates in Lao People's Democratic Republic: A Comparative Study of Plants Used in 66 Villages
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2010 (English)In: Journal of medical entomology, ISSN 0022-2585, Vol. 47, no 3, 400-414 p.Article in journal (Refereed) Published
Abstract [en]

Hematophagous parasites such as leeches, ticks, mites, lice, bedbugs, mosquitoes, and myiasis-producing fly larvae are common health problems in Lao People's Democratic Republic. Several arthropod-borne infections, e.g., malaria, dengue fever, and Japanese encephalitis, are endemic there. Effective vector control methods including the use of pesticides, insecticide-treated bed nets, and synthetic and plant-based repellents are important means of control against such invertebrates and the pathogens they may transmit or directly cause. In this study, we documented traditional knowledge on plants that are used to repel or kill hematophagous arthropods, including mosquitoes, bedbugs, human lice, mites and ticks, fly larvae, and blood-sucking leeches. Structured interviews were carried out in 66 villages comprising 17 ethnic groups, covering a range of cultures, throughout Lao People's Democratic Republic. A total of 92 plant species was recorded as traditional repellents (including plants for pesticidal usages) in 123 different plant-ectoparasite combinations. The number and species of plants, and animal taxa repelled (or killed) per plant species differed per region, village, and ethnic group. Traditional use was confirmed in the scientific literature for 74 of these plant species, and for an additional 13 species using literature on closely related species. The use of botanical repellents and pesticides from many plant species is common and widespread in the Lao countryside. In the future, the identification of the active components in certain plants to develop more optimal, inexpensive repellents, insecticides, acaricides, or antileech compounds as alternatives to synthetic repellents/pesticides against blood-feeding insects, ticks, mites, and leeches is warranted.

Keyword
botanical repellents, ethnobotany, leeches, mosquitoes, myiasis
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-136563 (URN)10.1603/ME09273 (DOI)000277597000015 ()20496588 (PubMedID)
Available from: 2010-12-14 Created: 2010-12-13 Last updated: 2012-03-29
2. Efficacy of essential oils of traditionally used plant species to repel mosquitoes in Vientiane capital Lao PDR:
Open this publication in new window or tab >>Efficacy of essential oils of traditionally used plant species to repel mosquitoes in Vientiane capital Lao PDR:
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(English)Manuscript (preprint) (Other academic)
Abstract [en]
Identifiers
urn:nbn:se:uu:diva-149989 (URN)
Available from: 2011-03-24 Created: 2011-03-24 Last updated: 2011-04-27
3. A Fly in the Ointment: Evaluation of Traditional Use of Plants to Repel and Kill Blowfly Larvae in Fermented Fish
Open this publication in new window or tab >>A Fly in the Ointment: Evaluation of Traditional Use of Plants to Repel and Kill Blowfly Larvae in Fermented Fish
2011 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 6, no 12, e29521Article in journal (Refereed) Published
Abstract [en]

Introduction: In rural areas in Laos, fly larvae infestations are common in fermenting fish. Blowflies (Chrysomyamegacephala, Diptera: Calliphoridae) are attracted to oviposit (and/or larviposit) onto fermenting fish which results ininfestations with fly larvae. Knowledge of traditional use of plants to repel larvae during the production of fermented fish iscommon and widespread in Lao PDR.

Research Questions: How effective are the most salient species in repelling, and killing fly larvae in fermenting fish?

Material and Methods: The three plant species most frequently reported to repel fly larvae during an ethnobotanical surveythroughout Lao PDR were tested for repellence and larvicidal activity of fly larvae infesting fermented fish. The lethality andrepellence of Tadehagi triquetrum (L.) H. Ohashi (Fabaceae), Uraria crinita (L.) Desv. ex DC. (Fabaceae) and Bambusa multiplex(Lour.) Raeusch. ex Schult. & Schult. f. (Poaceae) were tested in an experimental design using fermenting fish in Vientiane,Lao PDR.

Results: The repellent effect of fresh material of T. triquetrum and U. crinita, and the larvicidal effect of fresh B. multiplex, issignificantly more effective than that of dried material of the same species, and the total effect (repellence and larvicidaleffect combined) for each of the three species was significantly more effective for fresh than for dry material. Fresh materialof T. triquetrum, U. crinita, or B. multiplex added on top of the fermenting fish repelled 50%, 54%, 37%, and killed 22%, 28%,and 40% of fly larvae. The total effect was not significantly different per species at 72%, 82%, and 77%, respectively.

Discussion and Conclusions: The three most salient species are effective in repelling and killing fly larvae in the productionof fermented fish, and may be essential to augment food safety during traditional fermentation in open jars.

National Category
Agricultural Sciences Botany
Identifiers
urn:nbn:se:uu:diva-149968 (URN)10.1371/journal.pone.0029521 (DOI)000298665600041 ()
Available from: 2011-03-24 Created: 2011-03-24 Last updated: 2015-08-11Bibliographically approved
4. Keeping Leeches at Bay: Field Evaluation of Plant-Derived Extracts against Terrestrial Blood-Sucking Leeches (Haemadipsidae) in Lao PDR
Open this publication in new window or tab >>Keeping Leeches at Bay: Field Evaluation of Plant-Derived Extracts against Terrestrial Blood-Sucking Leeches (Haemadipsidae) in Lao PDR
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.

Keyword
Plant repellents, Leeches, Traditional Knowledge, Parasites
National Category
Microbiology
Identifiers
urn:nbn:se:uu:diva-149973 (URN)10.1016/j.actatropica.2011.05.014 (DOI)000293717200018 ()
Available from: 2011-03-24 Created: 2011-03-24 Last updated: 2015-08-12Bibliographically approved

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