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Find video protocols related to scientific articles indexed in Pubmed.
First report of an exophilic Anopheles arabiensis population in Bissau city, Guinea-Bissau: recent introduction or sampling bias?
Malar. J.
PUBLISHED: 08-08-2014
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The malaria vector Anopheles arabiensis exhibits greater behavioural and ecological plasticity than the other major vectors of the Anopheles gambiae complex, which presents challenges for major control methods. This study reports for the first time the presence of An. arabiensis in Antula, a suburb of Bissau city, the capital of Guinea Bissau, where high levels of hybridization between Anopheles coluzzii and An. gambiae have been reported. Given that previous surveys in the area, based on indoor collections, did not sample An. arabiensis, the possibility of a recently introduced exophilic population was investigated.
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Keeping leeches at bay: field evaluation of plant-derived extracts against terrestrial blood-sucking leeches (Haemadipsidae) in Lao PDR.
Acta Trop.
PUBLISHED: 03-14-2011
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Terrestrial blood-sucking leeches (Haemadipsidae) are common in the damp forests of the subtropical and tropical Indo-Pacific region. Members of the genus Haemadipsa are abundant in Laos and adjacent countries of Southeast Asia, and discomfort to people and livestock. Plant-derived repellents against arthropods 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 against mosquitoes but only a few on repellents against terrestrial blood-sucking leeches. Field experiments were conducted to evaluate the leech repellent activities of aqueous extracts of three traditionally used plant species, Sapindus rarak DC., Catunaregam spathulifolia Tirv. and Vernonia elaeagnifolia DC. Stockings impregnated 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 and DEET were 73.1% and 88.4%, respectively. An aqueous extract of S. rarak applied on cloth at a concentration of 1.9 mg/cm(2) is an effective and practical prevention method significantly reducing the number of blood-feeding leeches recorded on stockings worn by humans. This plant species is common in Southeast Asia and can be obtained at limited or no cost.
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The "far-west" of Anopheles gambiae molecular forms.
PLoS ONE
PUBLISHED: 02-15-2011
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The main Afrotropical malaria vector, Anopheles gambiae sensu stricto, is undergoing a process of sympatric ecological diversification leading to at least two incipient species (the M and S molecular forms) showing heterogeneous levels of divergence across the genome. The physically unlinked centromeric regions on all three chromosomes of these closely related taxa contain fixed nucleotide differences which have been found in nearly complete linkage disequilibrium in geographic areas of no or low M-S hybridization. Assays diagnostic for SNP and structural differences between M and S forms in the three centromeric regions were applied in samples from the western extreme of their range of sympatry, the only area where high frequencies of putative M/S hybrids have been reported. The results reveal a level of admixture not observed in the rest of the range. In particular, we found: i) heterozygous genotypes at each marker, although at frequencies lower than expected under panmixia; ii) virtually all possible genotypic combinations between markers on different chromosomes, although genetic association was nevertheless detected; iii) discordant M and S genotypes at two X-linked markers near the centromere, suggestive of introgression and inter-locus recombination. These results could be indicative either of a secondary contact zone between M and S, or of the maintenance of ancestral polymorphisms. This issue and the perspectives opened by these results in the study of the M and S incipient speciation process are discussed.
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Botanical repellents and pesticides traditionally used against hematophagous invertebrates in Lao Peoples Democratic Republic: a comparative study of plants used in 66 villages.
J. Med. Entomol.
PUBLISHED: 05-26-2010
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Hematophagous parasites such as leeches, ticks, mites, lice, bedbugs, mosquitoes, and myiasis-producing fly larvae are common health problems in Lao Peoples 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 Peoples 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.
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Acaricidal effects of Corymbia citriodora oil containing para-menthane-3,8-diol against nymphs of Ixodes ricinus (Acari: Ixodidae).
Exp. Appl. Acarol.
PUBLISHED: 01-24-2009
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The toxicity of para-menthane-3,8-diol (PMD), the main arthropod-repellent compound in the oil of the lemon eucalyptus, Corymbia citriodora, was evaluated against nymphs of Ixodes ricinus using five methods (A-E) of a contact toxicity bioassay. Mortality rates were estimated by recording numbers of dead nymphs at 30 min intervals during the first 5 h after the start of exposure and at longer intervals thereafter. The mortality rate increased with increasing concentration of PMD and duration of exposure with a distinct effect after 3.5 h. From the results obtained by methods A, C and E, the LC(50) range was 0.035-0.037 mg PMD/cm(2) and the LC(95) range was 0.095-0.097 mg PMD/cm(2) at 4 h of exposure; the LT(50) range was 2.1-2.8 h and the LT(95) range was 3.9-4.2 h at 0.1 mg PMD/cm(2). To determine the duration of toxic activity of PMD, different concentrations (0.002, 0.01, 0.1 mg PMD/cm(2)) were tested and mortality was recorded at each concentration after 1 h; thereafter new ticks were tested. This test revealed that the lethal activity of PMD remained for 24 h but appeared absent after 48 h. The overall results show that PMD is toxic to nymphs of I. ricinus and may be useful for tick control.
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Mosquito (Diptera: Culicidae) repellency field tests of essential oils from plants traditionally used in Laos.
J. Med. Entomol.
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Essential oils of Hyptis suaveolens (Lamiaceae), Croton roxburghii (Euphorbiaceae), and Litsea cubeba (Lauraceae) were tested in the field near Vientiane city, Lao PDR, on humans for repellent activity against mosquitoes. Landing mosquitoes were collected and later identified. The most abundant mosquitoes captured belonged to the genera Armigeres, Culex, and Aedes. All the plant oils tested at concentrations of 1.7 microg/cm(2), 3.3 microg/cm(2), and 6.3 microg/cm(2) were significantly more mosquito repellent than the negative control. Croton oil was significantly repellent against mosquitoes of the three genera at the highest (6.3 microg/cm(2)) concentration tested. Litsea oil was significantly repellent against Armigeres at all (1.7 microg/cm(2), 3.3 microg/cm(2), and 6.3 microg/cm(2)) concentrations tested. Hyptis oil was significantly repellent against Armigeres at 3.3 microg/cm(2) and 6.3 microg/cm(2) and against Culex at 1.7 microg/cm(2) and 6.3 microg/cm(2). The oils were analyzed for chemical content of volatiles, mainly terpenes. Main constituents were beta-pinene, sabinene, and 1,8-cineol from oils of the green parts of H. suaveolens; alpha-pinene, beta-pinene, and alpha-phellandrene from fresh bark of C. roxburghii; and alpha-pinene, beta-phellandrene, sabinene, and 1,8-cineol from fresh fruits of L. cubeba.
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Chemical composition and repellency of essential oils from four medicinal plants against Ixodes ricinus nymphs (Acari: Ixodidae).
J. Med. Entomol.
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In our search for effective tick repellents from plant origin, we investigated the effect of essential oils of four medicinal and culinary plants belonging to the family Lamiaceae on nymphs of the tick Ixodes ricinus (L.). The essential oils of the dry leaves of Rosmarinus officinalis (Rosemary) (L.), Mentha spicata (Spearmint) (L.), Origanum majorana (Majoram) (L.), and Ocimum basilicum (Basil) (L.) were isolated by steam distillation and 15 microg/cm2 concentration of oils was tested against ticks in a laboratory bioassay. The oils of R. officinalis, M. spicata, and O. majorana showed strong repellency against the ticks 100, 93.2, and 84.3%, respectively, whereas O. basilicum only showed 64.5% repellency. When tested in the field, the oils of R. officinalis and M. spicata showed 68.3 and 59.4% repellency at a concentration of 6.5 microg/cm2 on the test cloths. The oils were analyzed by gas chromatography mass spectrometry and the major compounds from the most repellent oils were 1,8-cineole, camphor, linalool, 4-terpineol, borneol, and carvone.
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