The potential economic benefits of controlling trypanosomiasis using waterbuck repellent blend in sub-Saharan Africa.

Trypanosomiasis is a significant productivity-limiting livestock disease in sub-Saharan Africa, contributing to poverty and food insecurity. In this paper, we estimate the potential economic gains from adopting Waterbuck Repellent Blend (WRB). The WRB is a new technology that pushes trypanosomiasis-transmitting tsetse fly away from animals, improving animals' health and increasing meat and milk productivity. We estimate the benefits of WRB on the production of meat and milk using the economic surplus approach. We obtained data from an expert elicitation survey, secondary and experimental sources. Our findings show that the adoption of WRB in 5 to 50% of the animal population would generate an economic surplus of US$ 78-869 million per annum for African 18 countries. The estimated benefit-cost ratio (9:1) further justifies an investment in WRB. The technology's potential benefits are likely to be underestimated since our estimates did not include the indirect benefits of the technology adoption, such as the increase in the quantity and quality of animals' draught power services and human and environmental health effects. These benefits suggest that investing in WRB can contribute to nutrition security and sustainable development goals.

Evaluation of the effectiveness of topical repellent distributed by village health volunteer networks against Plasmodium spp. infection in Myanmar: A stepped-wedge cluster randomised trial.

BACKGROUND: The World Health Organization has yet to endorse deployment of topical repellents for malaria prevention as part of public health campaigns. We aimed to quantify the effectiveness of repellent distributed by the village health volunteer (VHV) network in the Greater Mekong Subregion (GMS) in reducing malaria in order to advance regional malaria elimination. METHODS AND FINDINGS: Between April 2015 and June 2016, a 15-month stepped-wedge cluster randomised trial was conducted in 116 villages in Myanmar (stepped monthly in blocks) to test the effectiveness of 12% N,N-diethylbenzamide w/w cream distributed by VHVs, on Plasmodium spp. infection. The median age of participants was 18 years, approximately half were female, and the majority were either village residents (46%) or forest dwellers (40%). No adverse events were reported during the study. Generalised linear mixed modelling estimated the effect of repellent on infection detected by rapid diagnostic test (RDT) (primary outcome) and polymerase chain reaction (PCR) (secondary outcome). Overall Plasmodium infection detected by RDT was low (0.16%; 50/32,194), but infection detected by PCR was higher (3%; 419/13,157). There was no significant protection against RDT-detectable infection (adjusted odds ratio [AOR] = 0.25, 95% CI 0.004-15.2, p = 0.512). In Plasmodium-species-specific analyses, repellent protected against PCR-detectable P. falciparum (adjusted relative risk ratio [ARRR] = 0.67, 95% CI 0.47-0.95, p = 0.026), but not P. vivax infection (ARRR = 1.41, 95% CI 0.80-2.47, p = 0.233). Repellent effects were similar when delayed effects were modelled, across risk groups, and regardless of village-level and temporal heterogeneity in malaria prevalence. The incremental cost-effectiveness ratio was US$256 per PCR-detectable infection averted. Study limitations were a lower than expected Plasmodium spp. infection rate and potential geographic dilution of the intervention. CONCLUSIONS: In this study, we observed apparent protection against new infections associated with the large-scale distribution of repellent by VHVs. Incorporation of repellent into national strategies, particularly in areas where bed nets are less effective, may contribute to the interruption of malaria transmission. Further studies are warranted across different transmission settings and populations, from the GMS and beyond, to inform WHO public health policy on the deployment of topical repellents for malaria prevention. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry (ACTRN12616001434482).

Impact of Education on Knowledge and Practice of Kala Azar Preventive Measures among Seasonal and Migrant Agricultural Workers in Northwest Ethiopia.

Kala azar occurs among seasonal and migrant agricultural workers in northwest Ethiopia and accounts for almost 60% of the disease burden in the country. We conducted a quantitative study on the level of knowledge and practice of this vulnerable group in relation to kala azar transmission and acceptability of its vector control tools. A total of 403 workers were randomly selected from eight farms using a purposive sampling technique. Knowledge and practice scores were calculated based on 12 and 9 core questions, respectively. Binary logistic regression was used to identify factors associated with knowledge and practice. A large gap in knowledge of the disease and the vector was evident with 61.8%, 24.6%, and 13.6% of the workers having poor, moderate, and good levels of knowledge scores, respectively. Similarly, 95% of the seasonal workers reported poor level of use of protective measures against the bite of the sand fly vector. Good level of knowledge about kala azar and its sand fly vector was statistically associated with formal education (adjusted odds ratio [AOR] = 2.11; 95% CI = 1.17, 3.80; P < 0.05) and previous exposure to health education (AOR = 4.72; 95% CI = 1.99, 11.16; P < 0.001). Despite poor current knowledge and practice, a large proportion of the study participants showed interest in using vector control tools if made available, with 78% of the seasonal and migrant workers expressing some willingness to pay for different measures that can protect against sand fly bites. Therefore, we strongly recommend that comprehensive health education and vector control programs should be provided to these workers.

An Assessment of Household and Individual-Level Mosquito Prevention Methods during the Chikungunya Virus Outbreak in the United States Virgin Islands, 2014-2015.

Recent large-scale chikungunya virus (CHIKV) and Zika virus epidemics in the Americas pose a growing public health threat. Given that mosquito bite prevention and vector control are the main prevention methods available to reduce transmission of these viruses, we assessed adherence to these methods in the United States Virgin Islands (USVI). We interviewed 334 USVI residents between December 2014 and February 2015 to measure differences in mosquito prevention practices by gender, income, presence of CHIKV symptoms, and age. Only 27% (91/334) of participants reported having an air conditioner, and of the 91 with air-conditioners, 18 (20%) reported never using it. Annual household income > $50,000 was associated with owning and using an air conditioner (41%; 95% confidence interval [CI]: 28-53% compared with annual household income ≤ $50,000: 17%; 95% CI: 12-22%). The majority of participants reported the presence of vegetation in their yard or near their home (79%; 265) and a cistern on their property (78%; 259). Only 52 (16%) participants reported wearing mosquito repellent more than once per week. Although the majority (80%; 268) of participants reported having screens on all of their windows and doors, most (82%; 273) of those interviewed still reported seeing mosquitoes in their homes. Given the uniformly low adherence to individual- and household-level mosquito bite prevention measures in the USVI, these findings emphasize the need for improved public health messaging and investment in therapeutic and vaccine research to mitigate vector-borne disease outbreaks.

The prevention of canine leishmaniasis and its impact on public health.

Canine leishmaniasis (CanL) caused by Leishmania infantum is a vector-borne disease of great veterinary and medical significance. Prevention of CanL requires a combined approach including measures focused on dogs and the environment where the vectors perpetuate. Over past decades, considerable effort has been put towards developing novel and cost-effective strategies against CanL. Vaccination is considered among the most promising tools for controlling CanL, and synthetic pyrethroids are useful and cost-effective in reducing risk of L. infantum infection in dogs. The effectiveness of the use of vaccines plus repellents in preventing L. infantum infection and subsequent disease development should be assessed by means of large-scale, randomized controlled field trials because this combined strategy may become the next frontier in the control of CanL.

Microencapsulated citronella oil for mosquito repellent finishing of cotton textiles.

Microcapsules containing citronella essential oil were prepared by complex coacervation and applied to cotton textiles in order to study the repellent efficacy of the obtained fabrics. Citronella released from treated textiles was indirectly monitored by the extractable content of its main components. Repellent activity was assessed by exposure of a human hand and arm covered with the treated textiles to Aedes aegypti mosquitoes. Fabrics treated with microencapsulated citronella presented a higher and longer lasting protection from insects compared to fabrics sprayed with an ethanol solution of the essential oil, assuring a repellent effect higher than 90% for three weeks. Complex coacervation is a simple, low cost, scalable and reproducible method of obtaining encapsulated essential oils for textile application. Repellent textiles were achieved by padding cotton fabrics with microcapsules slurries using a conventional pad-dry method. This methodology requires no additional investment for textile finishing industries, which is a desirable factor in developing countries.

Visceral leishmaniasis on the Indian sub-continent: a multi-centre study of the costs of three interventions for the control of the sandfly vector, Phlebotomus argentipes.

The sandflies that transmit the parasites causing human visceral leishmaniasis (VL) can be controlled by several methods, including indoor residual spraying (IRS), the use of long-lasting insecticidal nets (LLIN) and ecological vector management (EVM). The financial costs of each of these three methods of sandfly control have recently been assessed and compared, in a multi-centre study based on the Indian sub-continent. In each of the four study sites (two in Nepal and one each in India and Bangladesh), 24 neighbourhoods were randomly selected in districts with high incidences of VL. The costs of the three interventions were then prospectively assessed in each study neighbourhood, in the local currency, and then converted to U.S. dollars at the prevailing exchange rate in the country concerned. The costs of IRS, which ranged from U.S.$2.4-11.7 (mean = U.S.$5.9) per household-year, were greater than those of LLIN (U.S.$3.5-5.1/household-year, with a mean of U. S.$4.5) but less than those of EVM (U. S.$5.0- 14.0/household-year, with a mean of U.S.$8.7). These results indicate that LLIN and IRS may be the cheaper options for the control of sandflies on the Indian sub-continent, and that EVM should perhaps only be taken up as a complimentary and voluntary method. Various combinations of these interventions (based on country-specific social and economic factors) may, however, be the best and most cost-effective choice.

Personal-protection measures against mosquitoes: a study of practices and costs in a district, in the Indian state of Orissa, where malaria and lymphatic filariasis are co-endemic.

In a study undertaken among rural and urban communities in a district of Orissa, India, the personal-protection measures used against mosquitoes, and the household costs of these measures, were investigated. Most people living in the study communities perceived mosquitoes as a problem, both as a biting nuisance and as vectors of human disease. Almost all (99%) of the urban households investigated and most (84%) of the rural each reported the use of at least one measure against mosquitoes. Most of the study households (92% of the urban and 64% of the rural) used a 'modern' chemical method (coils, vaporizing mats, liquid vaporizers or sprays), with mosquito coils used more frequently than any other personal-protection measure. Untreated bednets were also used by most of the households investigated (76% of the urban and 58% of the rural) and some households (about 10% of the urban and 8% of the rural) still used the more traditional method of burning dried dung or vegetation indoors, specifically to create smoke to drive away mosquitoes. Setting, house type, as indicated by the material used as roofing, and number of people in the household were each a significant predictor of the use of personal protection, with households in an urban setting, large households, and households occupying a concrete-roofed building relatively more likely to use some form of personal protection. Although 'modern', chemical-based methods were frequently employed, about one in every two interviewees (57% of the urban and 43% of the rural) considered the use of such methods to be harmful to their health. The mean monthly expenditures on personal-protection measures were 101 Indian rupees (U.S.$2.20)/urban household and 72 Indian rupees (U.S.$1.60)/rural household. Setting, family income, family size and number of sleeping rooms in the house each affected such expenditure significantly. As a proportion of household income, expenditure on controlling mosquitoes was surprisingly high.

A low-cost repellent for malaria vectors in the Americas: results of two field trials in Guatemala and Peru.

BACKGROUND: The cost of mosquito repellents in Latin America has discouraged their wider use among the poor. To address this problem, a low-cost repellent was developed that reduces the level of expensive repellent actives by combining them with inexpensive fixatives that appear to slow repellent evaporation. The chosen actives were a mixture of para-menthane-diol (PMD) and lemongrass oil (LG). METHODS: To test the efficacy of the repellent, field trials were staged in Guatemala and Peru. Repellent efficacy was determined by human-landing catches on volunteers who wore the experimental repellents, control, or 15% DEET. The studies were conducted using a balanced Latin Square design with volunteers, treatments, and locations rotated each night. RESULTS: In Guatemala, collections were performed for two hours, commencing three hours after repellent application. The repellent provided >98% protection for five hours after application, with a biting pressure of >100 landings per person/hour. The 15% DEET control provided lower protection at 92% (p < 0.0001). In Peru, collections were performed for four hours, commencing two hours after repellent application. The PMD/LG repellent provided 95% protection for six hours after application with a biting pressure of >46 landings per person/hour. The 20% DEET control provided significantly lower protection at 64% (p < 0.0001). CONCLUSION: In both locations, the PMD/LG repellent provided excellent protection up to six hours after application against a wide range of disease vectors including Anopheles darlingi. The addition of fixatives to the repellent extended its longevity while enhancing efficacy and significantly reducing its cost to malaria-endemic communities.

Traditional use of indigenous mosquito-repellents to protect humans against mosquitoes and other insect bites in a rural community of Cameroon.

OBJECTIVE: To document and test the efficacy of indigenous traditional personal protection methods against mosquito bites and general nuisance. DESIGN: A prospective study based on a survey and field evaluation of selected plant-based personal protection methods against mosquito bites. SETTING: Bolifamba, a rural setting of the Mount Cameroon region. SUBJECTS: A structured questionnaire was administered to 179 respondents and two anti-mosquito measures were tested under field conditions. MAIN OUTCOME MEASURES: Identified traditional anti-mosquito methods used by indigenes of Bolifamba. Two plants tested under field conditions were found to be effective. RESULTS: Of the 179 respondents, 88 (49.16%) used traditional anti-mosquito methods; 57 (64.77%) used plant-based methods while 31 (35.2%) used various petroleum oils. The rest of the respondents, 91 (50.8%) used conventional personal protection methods. Reasons for using traditional methods were because they were available, affordable and lack of known more effective alternatives. The demerits of these methods were: labourious to implement, stain dresses, produce a lot of smoke/ repulsive odours when used; those of conventional methods were lack of adequate information about them, high cost and non-availability. When the two most frequently used plants, Saccharum officinarium and Ocimum basilicum were evaluated under field conditions, each gave a better protection than the control. CONCLUSION: Most plants used against mosquitoes in the area are known potent mosquito repellents but others identified in the study warrant further research. The two tested under field conditions were effective though less than the commonly used commercial diethyltoluamide.

Picardin--a new insect repellent.

An alternative to DEET for protection against mosquitoes.

Personal protection against mosquitoes in Dar es Salaam, Tanzania, by using a kerosene oil lamp to vaporize transfluthrin.

The effectiveness of a cheap and easy method of household protection against Culex quinquefasciatus Say and other mosquitoes (Diptera: Culicidae) was investigated in Dar es Salaam, Tanzania. Kerosene-burning lamps (korobois) were modified to heat and vaporize transfluthrin, a volatile pyrethroid insecticide. When transfluthrin was added to fuel of the lamp, protection against biting was poor unless a very high concentration of insecticide was used. A modified lamp (= vaporizing koroboi) was designed to overcome this problem by mixing the insecticide with vegetable oil and heating it to 120 degrees C in a tin held just above the flame. The concentration of 0.1% transfluthrin in vegetable oil gave 50-75% reduction in biting, a similar degree of protection to that obtained from burning a mosquito coil containing a synthetic pyrethroid (0.25% d-allethrin) and significantly better protection than a locally bought coil (brand 'White Crane', probably containing DDT). Greater protection (consistently > 90%) was achieved with a higher concentration of transfluthrin (0.5%) in the vegetable oil. This modified lamp is simple, cheap and employs locally available technology. With further development, and due regard to inhalation toxicity of the vaporized materials, it may offer a more cost-effective alternative to a mosquito coil as a means of personal protection, and a useful complement to a net for the early part of the evening before bedtime.

An appropriate method for extracting the insect repellent citronellol from an indigenous plant (Pelargonium graveolens L'Her) for potential use by resource-limited animal owners.

Veterinary needs appraisals in rural, peri-urban and urban areas have indicated a need for affordable and accessible veterinary health care. It was also found that farmers and animal owners used indigenous plants for treating animals. In Africa, insects such as Culex, Culicoides and Stomoxys may transmit diseases, cause irritation to animals or prevent wound healing. Insect repellents used topically are generally safer and cheaper than insecticides. Using readily available commercial sources of ethanol 43% v/v (brandy and cane spirits), it was shown that citronellol could be extracted from uncrushed leaves of the indigenous shrub Pelargonium graveolens L'Hér. Efficacy of extraction was compared to that using reagent grade absolute ethanol. The peak concentration of citronellol was achieved within 7 days of extraction and thereafter remained constant for 4 months. Extraction methods using tap water and cooking oil were not successful. The extraction was also less successful when the leaves were crushed or macerated before being placed into ethanol. Gas chromatography was used to monitor the concentration of citronellol in the different extracts.

Role of repellents in vector control and disease prevention.

Repellents are an inexpensive and practical means of protection against nuisance and disease vector arthropods in conjunction with or when other control measures are not feasible. Appropriate selection of skin and/or clothing repellents along with proper wear of clothing can provide adequate protection from biting arthropods, and are available in a wide variety of forms including lotions, creams, foams, soaps, aerosols, sticks, and towellettes. A coordinated effort among different research groups associated with advances in the science of insect repellents such as mode of action information, doses of repellents to generate threshold level responses and controlled release delivery mechanisms, may help in understanding the mechanisms by which repellents work. This in turn may revolutionize the development of repellents for personal protection and their use in vector control.