The objective of the test was to determine the Complete Protection Time of NO MAS repellent (NO MO), when applied at a typical consumer dose, again wild populations of mosquitos including but not limited to species of the genera Culex, Anopheles, and Aedes, to provide data under the Data-Call-In requirements (EPA Reg. No. 3126-LRN0) of United States Environmental Protection Agency Guideline OPPTS 810.3700.
This mosquito repellent study was sponsored by Mr. Sam Darling of the Del Cielo foundation (Salt Spring Island, British Columbia, Canada), to provide efficacy data in support of a pesticide registration application to the United States Environmental Protection Agency. The test material, based on the active ingredients p-menthane-3,8-diol (PMD) and lemongrass oil (citral), is No Mas, a topical lotion repellent.
The study Protocol was reviewed and approved by Independent Investigational Review Board, Inc., and reviewed favorably by the US Environmental Protection Agency and its Human Studies Review Board, and by the California Environmental Protection Agency.
We conducted a dosimetry study in advance of efficacy testing in order to estimate typical consumer dosing behavior. The resulting average dosing rates, of 1.20 μl/cm2 on arms and 1.04 μl/cm2 on legs, were then employed as the rates for the subjects in the field efficacy study. These results were also used to estimate the Margin of Exposure (MOE) relative to acute dermal toxicity limit dose in No Mas (>5000 mg/kg, see toxicity test reports), resulting in Margin of Exposure (MOE) values of >583 (arms) and >287 (legs) for the repellent. We judged these margins to be sufficiently great to justify dermal exposure of the subjects to the test materials during efficacy testing.
Efficacy was tested in two different habitats under expected environmental conditions for consumers using the product. In each habitat, ten human subjects (five female, five male) each exposed a No Mas repellent-treated limb to mosquitoes for one minute every 15 minutes, until product failure or cessation of the test. Simultaneously, one male and one female untreated control subject exposed arms or legs in the same manner, in order to assess mosquito biting pressure. Both controls experienced landings within one minute of exposure throughout each test day, indicating that mosquitoes were suitably active for the efficacy study.
Under field conditions, the repellent provided substantial and prolonged protection against the mosquito species (Aedes melanimon, Ae. vexans, Ae.nigromaculis, Culex tarsalis, and Anopheles freeborni). Mean Complete Protection Time (CPT) for No Mas was 9.8 hours at Site 1 and 10.1 hours at Site 2.
In summary, No Mas repellent at 16% PMD and 2% lemongrass oil concentrations provided prolonged periods of Complete Protection against several species of mosquitoes, including species significant to public health.
The average protective efficacy of NM against Anopheles mosquitoes over 9 hours was 89.6%. Controls averaged 86 bites/person/night versus 9 bites/ person/night with the use of NM. Use of repellent was associated with a decrease of absolute malaria prevalence by 19.2% in the repellent village and by 6.5% in the control village (45.5 to 26.3, and 29.5 to 23.0, respectively). The user acceptance rate of NM repellent was 96.1%. Ten percent (10%) of repellent users reported irritation as the main adverse effect during the period. Eighty-five percent (85%) of the users found the odor of NM appealing and 87% reported no inconvenience in applying the repellent daily.
Background & objective: Probability models for assessing a mosquito repellent’s potential to reduce malaria transmission are not readily available to public health researchers. To provide a simple means for estimating the epidemiological efficacy of mosquito repellents in communities, we develop a simple mathematical model.
Study design: A static probability model is presented to simulate malaria infection in a community during a single transmission season. The model includes five parameters—sporozoite rate, human infection rate, biting pressure, repellent efficacy, and product-acceptance rate.
Interventions: The model assumes that a certain percentage of the population uses personal mosquito repellents over the course of a seven-month transmission season and that this repellent maintains a constant rate of protective efficacy against the bites of malaria vectors.
Main outcome measures: This model measures the probability of completely evading infection over a seven-month period at diverse rates of vector biting pressure, repellent efficacy, and product acceptance.
Results & conclusion: Absolute protection using mosquito repellents alone requires high rates of repellent efficacy and product acceptance. Using performance data from a highly effective repellent, the model estimates an 88.9% reduction of infections over a seven-month transmission season. A corresponding and proportional reduction in the incidence of super-infection in community members not completely evading infection can also be presumed. Thus, the model shows that mass distribution of a repellent with >98% efficacy and >98% product acceptance would suppress new malaria infections to levels lower than those achieved with insecticide treated nets (ITNs). A combination of both interventions could create synergies that result in reductions of disease burden significantly greater than with the use of ITNs alone.
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 Å~ repellent effect (F = 1. 731, d.f. = 48, P = 0. 209).