Ethnobotanical study of some of mosquito repellent plants in north-eastern Tanzania

Tropical Pesticides Research Institute, Division of Livestock and Human Disease Vectors Control, P,O, Box 3024, Arusha,Tanzania.
Malaria Journal (Impact Factor: 3.11). 02/2008; 7(1):152. DOI: 10.1186/1475-2875-7-152
Source: PubMed


The use of plant repellents against nuisance biting insects is common and its potential for malaria vector control requires evaluation in areas with different level of malaria endemicity. The essential oils of Ocimum suave and Ocimum kilimandscharicum were evaluated against malaria vectors in north-eastern Tanzania.
An ethnobotanical study was conducted at Moshi in Kilimanjaro region north-eastern Tanzania, through interviews, to investigate the range of species of plants used as insect repellents. Also, bioassays were used to evaluate the protective potential of selected plants extracts against mosquitoes.
The plant species mostly used as repellent at night are: fresh or smoke of the leaves of O. suave and O. kilimandscharicum (Lamiaceae), Azadirachta indica (Meliaceae), Eucalyptus globules (Myrtaceae) and Lantana camara (Verbenaceae). The most popular repellents were O. kilimandscharicum (OK) and O. suave (OS) used by 67% out of 120 households interviewed. Bioassay of essential oils of the two Ocimum plants was compared with citronella and DEET to study the repellence and feeding inhibition of untreated and treated arms of volunteers. Using filter papers impregnated with Ocimum extracts, knockdown effects and mortality was investigated on malaria mosquito Anopheles arabiensis and Anopheles gambiae, including a nuisance mosquito, Culex quinquefasciatus. High biting protection (83% to 91%) and feeding inhibition (71.2% to 92.5%) was observed against three species of mosquitoes. Likewise the extracts of Ocimum plants induced KD90 of longer time in mosquitoes than citronella, a standard botanical repellent. Mortality induced by standard dosage of 30 mg/m2 on filter papers, scored after 24 hours was 47.3% for OK and 57% for OS, compared with 67.7% for citronella.
The use of whole plants and their products as insect repellents is common among village communities of north-eastern Tanzania and the results indicate that the use of O. suave and O. kilimandscharicum as a repellent would be beneficial in reducing vector biting. The widespread use of this approach has a potential to complement other control measures.

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    • "More innovative vector control strategies including control of resistant vector populations in the sub-region are use of entomopathogenic fungi [35, 36], larval source management [7] and vector trapping373839. Plant-based derivatives have also been used in vector control in Uganda [40], Tanzania414243, Kenya [44, 45] and Ethiopia464748. "
    [Show abstract] [Hide abstract] ABSTRACT: Malaria is a major contributor to the global disease burden and a significant impediment to socioeconomic development in resource-poor countries. In contrast to improved trends of malaria morbidity and mortality in some parts of the world, malaria has re‐ mained a life threatening disease in many other regions including East Africa because of factors such as weak health systems, growing drug and insecticide resistance, ecological change, climate anomalies, socioeconomic factors and changes in land use patterns. On‐ going malaria vector control strategies rely mainly on the use of indoor residual spraying (IRS) and insecticide treated nets (ITNs) which are the primary intervention strategies to reduce malaria burden. The current success in reducing malaria related morbidity and mortality has led to the optimism that elimination of the disease as a public health prob‐ lem may be a realistic objective. Efforts during the last decades enabled access to ITNs in sub-Saharan Africa protecting millions of people at risk of malaria. The number of coun‐ tries that employed IRS as a vector control strategy increased almost by two fold and the percentage of households owing at least one ITN in sub-Saharan Africa is estimated to increase from time to time. Currently, all ITNs are treated with pyrethroids while IRS de‐ pends on pyrethroids, DDT and recently on carbamates. Despite IRS and ITNs are known in reducing malaria incidence, insecticide resistance in malaria vectors threatens the suc‐ cess of malaria control program. Resistance to insecticides has occurred in most arthro‐ pod vectors with different mechanisms. If the current trends of increased insecticide resistance continue, it may jeopardise the efficacy of current vector control tools. Given the limited choice of available insecticides, i.e., only 12 insecticides belonging to 4 classes of insecticides (organochlorines, organophosphates, pyrethroids and carbamates), resist‐ ance to these insecticides has become a limiting factor for current efforts to sustain con‐ trol. Currently, no other insecticide class with similar efficacy has been approved by WHOPES. The development of insecticide resistance in malaria vectors has been attribut‐ ed to the prolonged use of insecticides for IRS and high coverage of ITNs/LLINs. The re‐ cent use of pyrethroids for indoor residual spraying is likely to have enhanced the selection pressure for insecticide resistance alleles among East African vector popula‐ tions. Moreover, mosquitoes breeding in agricultural habitats are exposed to sub lethal
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    • "In Guinea Bissau, 55% of people burn plants to repel mosquitoes [40]. The result is also comparable to a study reported by Kweka et al., [34]. The use of plant leaves as insect repellent could be one of more sustainable options than any other parts like roots, resin and bark. "
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    Full-text · Article · Feb 2014 · Journal of Ethnobiology and Ethnomedicine
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    • "The result of this study also indicated that the majority (73%) of local community members use smoking of the plant part by burning to repel mosquitoes. Similar results have been reported in previous studies carried out in Ethiopia and Tanzania indicating most of the local communities apply smoke to drive away mosquito (Karunamoorthi et al., 2009a; Kweka et al., 2008). In addition, the results also indicated that other types of application such as macerating the plant, laying the leaves of plants inside the house and rubbing onto cloths/skin are important. "
    [Show abstract] [Hide abstract] ABSTRACT: Insect repellents have been used to reduce human-vector contact for long periods of time in different parts of the world. Thus, the aim of this study was to assess the knowledge of traditional mosquito repellent plants among inhabitants of Kolla Temben district, Ethiopia. Two hundred and forty households were selected for an ethnobotanical survey using stratified, systematic random sampling. One adult leader from each household was interviewed on her or his knowledge about traditional mosquito repellent plants. The ethnobotanical survey was carried out from January-March, 2010. Data analysis was carried out using SPSS, version 16. The level of significance was determined using 95% confidence interval. Ninety-five percent of the respondents had knowledge regarding traditional mosquito repellent plants. Application of smoke by burning (73%) the parts plants was the most common practice among the inhabitants. There was no significant association between knowledge of traditional mosquito repellent plants with age (p = 0.402), sex (p = 0.067) or educational status (p = 0.052) of the respondents. Moreover, the survey revealed that the most commonly known traditional mosquito repellent plants were Otostegia integrifolia (41.7%), Silene macroserene (24.6%,) (Olea europeae (22.5%), Melia azedarach (17.5%), Calpurnia aurea (9.6%), Dodonaea angustifolia (8.7%), Eucalyptus globulus (8.3%), Ere (Aloe spp) 6.7% and Sasa (Otostegia fruticosa) 2.5%. These preliminary findings suggested that the studied community has potentially important knowledge about traditional mosquito repellent plants. Therefore, further study on conserving the knowledge and evaluating the efficacy of the plants must be done.
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