Efficacy of DEET and non-DEET-based insect repellents against bites of Simulium damnosum vectors of onchocerciasis.

Coping strategies including smoke screens are used against nuisance bites of Simulium damnosum Theobald (Diptera:Simuliidae) in onchocerciasis endemic communities. To find more effective alternatives, the efficacy of commercially available N,N-diethyl-3-methylbenzamide (DEET) products with active concentrations of 9.5, 13, 25, 50 and 98.1-100% and 'NO MAS,' (active component: para-menthane-3,8-diol and lemon grass oil) were tested at Bui-Agblekame, Ghana. A Latin square study design was implemented using eight groups of two vector collectors each, who used repellents (treatment), mineral oil or nothing each day until the end of the study. Flies were caught and their numbers each hour recorded using the standard methods for onchocerciasis transmission studies. T-tests were used to compare the mean duration of protection and a one-way analysis of variance controlling for catchers and repellents was performed. Tukey's test was used to compare protection by repellents and mineral oil. The highest percentage protection was 80.8% by NO MAS and the least 42.5% by the 13% DEET product. The period of absolute protection was 5 h by NO MAS and 1 h by 50% DEET product. No significant increase in protection was offered beyond 25% active DEET products and no significance was observed in terms of catcher × repellent effect (F = 1.731, d.f. = 48, P = 0.209).

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.

A review of recommendations on the safe and effective use of topical mosquito repellents.

Mosquito-borne disease is an annual problem in Australia, with endemic pathogens such as Ross River virus infecting thousands of people each year. The recent emergence of Zika virus in South America and the Pacific, together with ongoing outbreaks of dengue viruses in Southeast Asia, generated great community interest in the most effective strategies to avoid mosquito bites. Large-scale mosquito control programs are not common in Australia and are limited in New South Wales (NSW). The use of topical insect repellents is a key recommendation by health authorities to prevent mosquito-borne disease. All products sold in Australia purporting to repel mosquitoes must be registered with the Australian Pesticides and Veterinary Medicines Authority. Despite around 100 commercial products registered as repelling mosquitoes, there are relatively few active ingredients used across these formulations. The most common are diethyltoluamide (DEET), picaridin, p-menthane-3,8-diol (PMD) and a range of plant-derived products (e.g. melaleuca, eucalyptus, citronella oils). Research has shown that each of these active ingredients varies in the duration of protection provided against biting mosquitoes. Recommendations by health authorities are informed by this research, but inconsistencies between recommendations and available repellent formulations and their concentration of active ingredients can cause confusion in the community. There are conflicts between the data resulting from scholarly research, marketing promotion by manufacturers and recommendations provided by overseas health authorities. A review was undertaken of NSW Health's current recommendations on choosing and using insect repellents, taking into consideration recent research and currently registered topical repellents.

Repellency of IR3535, KBR3023, para-menthane-3,8-diol, and deet to black salt marsh mosquitoes (Diptera: Culicidae) in the Everglades National Park.

IR3535, KBR3023, para-Menthane-3,8-diol (PMD), and deet were evaluated in controlled studies with human subjects (n = 5) for repellency to black salt marsh mosquitoes (Ochlerotatus taeniorhynchus Wiedemann), in the Everglades National Park, FL. In tests of 6-h duration, with an average mosquito biting pressure on exposed forearm skin of 19.5 (+/- 13.7) bites per minute, the mean percent repellencies (SE) for IR3535, KBR3023, PDM, and deet was 88.6 (3.2), 97.5 (1.7), 89.2 (2.9), and 94.8 (2.5), respectively. Mean complete protection times (SE) for IR3535, KBR3023, PMD), mean deet were 3.0 (1.0), 5.4 (0.6), 3.8 (1.4), and 5.6 (0.5) h, respectively. Untreated (ethanol) controls provided 0% repellency. When mosquito biting rates on the untreated forearm skin of repellent-treated subjects were compared with biting rates on the forearm skin of control subjects, the former were 23%-40% lower early in tests and as much as 22% higher late in tests. These differences cast doubt on the technical merit of test designs comprising evaluation of more than one repellent at a time on the same human subject while underscoring the importance of untreated subjects as negative controls in field repellent bioassays.

A comparison of four root canal filling techniques.

This study compared the apical seal produced by four obturation techniques. Sixty-four extracted human teeth were prepared and obturated using lateral condensation of gutta-percha that was either unmodified or was dipped in chloroform, eucalyptol, or eucapercha paste. After storage in normal saline and 0.02% azide solution at 37 degrees C for 200 days, the teeth were immersed in India ink for 48 h. The most coronal extent of leakage of India ink into the canal was then determined. Significantly more apical leakage occurred in the eucapercha group than in the other three groups. All other comparisons were equivalent. The results suggest that modification of the gutta-percha master cone with solvent does not improve the apical seal in vitro. If modification is desired, then dipping the master cone in either eucalyptol or chloroform produces an apical seal superior to that achieved with eucapercha.

A comparison of apical seal: chloroform versus eucalyptol-dipped gutta-percha obturation.

Three groups of extracted teeth were obturated using gutta-percha and lateral condensation. In one group the gutta-percha was dipped in chloroform before condensation. In a second a eucalyptol dip was used. No dip was used in the third group. A dye penetration study was done to compare leakage among the three groups. The teeth were cleared for viewing and measurements of dye penetration were made using a stereomicroscope. Statistical analysis using Kruskal-Wallis one-way analysis of variance of the results showed no significant difference among test groups at the 0.05 level.

Field evaluation of three plant-based insect repellents against malaria vectors in Vaca Diez Province, the Bolivian Amazon.

The efficacy of repellents against Anopheles darlingi, the main malaria vector in Bolivia, was evaluated. This mosquito has a peak in biting activity early in the evening. Three natural repellents (1 eucalyptus based, 1 neem based, and 1 containing several repellent essential oils) were tested in comparison with 15% deet in human landing catches in Bolivia. The eucalyptus-based repellent containing 30% p-menthane-diol applied at a dose similar to those used in practice gave 96.89% protection for 4 h. Deet gave 84.81% protection. The other 2 products did not provide significant protection from mosquito bites.

[Field efficacy of repellent formulation containing para-menthane-3,8-diol and lemongrass against Culicoides pachymerus (Diptera: Ceratopogonidae) in Colombia]. / Eficacia en campo de un repelente a base de para-mentano-3,8-diol y aceite de limonaria contra Culicoides pachymerus (Diptera: Ceratopogonidae) en Colombia.

INTRODUCTION: Culicoides pachymerus is a major pest species for the inhabitants of the western Boyacá province of Colombia. OBJECTIVE: The effect of a repellent lotion based on p-menthane-3,8-diol (16%) and lemongrass oil (2%) was evaluated against the bites of C. pachymerus. MATERIALS AND METHODS: The repellent lotion was compared simultaneously with a control (no treatment) by human landing catches of C. pachymerus on the forearms of paired volunteers situated near human dwellings. Protection percentage and protection time for 3 to 6 h after repellent application was calculated. The test was repeated ten times. RESULTS: Only two females of C. pachymerus were collected on arms with the repellent treatment. In contrast, the mean biting rate in the untreated control was 47.7 midges/person/10 min. Mean protection percentage of the repellent was 100% up to 4 h and 99.5% up to 5 h. Protection time was 332.2 and 338.2 min in the two replicates where bites of C. pachymerus were confirmed. In the remaining eight replicates protection time exceeded the test duration. CONCLUSION: The repellent showed high efficacy against C. pachymerus, up to 5 h post-application.

Protective efficacy of menthol propylene glycol carbonate compared to N, N-diethyl-methylbenzamide against mosquito bites in Northern Tanzania.

BACKGROUND: The reduction of malaria parasite transmission by preventing human-vector contact is critical in lowering disease transmission and its outcomes. This underscores the need for effective and long lasting arthropod/insect repellents. Despite the reduction in malaria transmission and outcomes in Tanzania, personal protection against mosquito bites is still not well investigated. This study sought to determine the efficacy of menthol propylene glycol carbonate (MR08), Ocimum suave as compared to the gold standard repellent N, N-diethyl-methylbenzamide (DEET), either as a single dose or in combination (blend), both in the laboratory and in the field against Anopheles gambiae s.l and Culex quinquefasciatus. METHODS: In the laboratory evaluations, repellents were applied on one arm while the other arm of the same individual was treated with a base cream. Each arm was separately exposed in cages with unfed female mosquitoes. Repellents were evaluated either as a single dose or as a blend. Efficacy of each repellent was determined by the number of mosquitoes that landed and fed on treated arms as compared to the control or among them. In the field, evaluations were performed by human landing catches at hourly intervals from 18:00 hr to 01:00 hr. RESULTS: A total of 2,442 mosquitoes were collected during field evaluations, of which 2,376 (97.30%) were An. gambiae s.l while 66 (2.70%) were Cx. quinquefaciatus. MR08 and DEET had comparatively similar protective efficacy ranging from 92% to 100 for both single compound and blends. These findings indicate that MR08 has a similar protective efficacy as DEET for personal protection outside bed nets when used singly and in blends. Because of the personal protection provided by MR08, DEET and blends as topical applicants in laboratory and field situations, these findings suggest that, these repellents could be used efficiently in the community to complement existing tools. Overall, Cx. quinquefasciatus were significantly prevented from blood feeding compared to An. gambiae s.l. CONCLUSION: The incorporation of these topical repellents for protection against insect bites can be of additional value in the absence or presence of IRS and ITNs coverage. However, a combination of both the physical (bed nets) and the repellent should be used in an integrated manner for maximum protection, especially before going to bed. Additional research is needed to develop repellents with longer duration of protection.