Isolation of Volatile Compounds with Repellent Properties against Aedes albopictus (Diptera: Culicidae) Using CPC Technology.

The present work describes the use of Centrifugal Partition Chromatography (CPC) for the bio-guided isolation of repellent active volatile compounds from essential oils. Five essential oils (EOs) obtained from three Pinus and two Juniperus species were initially analyzed by gas chromatography-mass spectrometry (GC/MS) and evaluated for their repellent properties against Aedes albopictus. The essential oil from needles of P. pinea (PPI) presented the higher activity, showing 82.4% repellency at a dose of 0.2 µL/cm2. The above EO, together with the EO from the fruits of J. oxycedrus subsp. deltoides (JOX), were further analyzed by CPC using the biphasic system n-Heptane/ACN/BuOH in ratio 1.6/1.6/0.2 (v/v/v). The analysis of PPI essential oil resulted in the recovery of (-)-limonene, guaiol and simple mixtures of (-)-limonene/ß-pheladrene, while the fractionation of JOX EO led to the recovery of ß-myrcene, germacrene-D, and mixtures of α-pinene/ß-pinene (ratio 70/30) and α-pinene/germacrene D (ratio 65/45). All isolated compounds and recovered mixtures were tested for their repellent activity. From them, (-)-limonene, guaiol, germacrene-D as well the mixtures of (-)-limonene/ß-pheladrene presented significant repellent activity (>97% repellency) against Ae. albopictus. The present methodology could be a valuable tool in the effort to develop potent mosquito repellents which are environmentally friendly.

Persistence Enhancement of a Promising Tick Repellent, Benzyl Isothiocyanate, by Yeast Microcarriers.

Phenethyl isothiocyanate isolated from Armoracia rusticana root oil and its derivatives were tested at different doses in a bioassay designed to evaluate repellency against individual Haemaphysalis longicornis nymphs. Among the tested compounds, benzyl isothiocyanate exhibited repellency against H. longicornis nymphs at the lowest dose of 0.00625 mg/cm2, followed by phenethyl isothiocyanate (0.0125 mg/cm2) and phenyl isothiocyanate (0.025 mg/cm2). The behavioral responses of H. longicornis nymphs exposed to benzyl isothiocyanate and phenethyl isothiocyanate indicated that the mode of action of these compounds can be mainly attributed to the vapor phase. Encapsulated benzyl isothiocyanate showed repellency up to 120 min post-application at 0.1 mg/cm2, whereas pure benzyl isothiocyanate showed repellency up to 60 min post-application at 0.1 mg/cm2. The present study suggests that benzyl isothiocyanate is a potential repellent for protection against H. longicornis nymphs, and encapsulation in yeast cells may enhance the repellency effect.

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).

orco mutant mosquitoes lose strong preference for humans and are not repelled by volatile DEET.

Female mosquitoes of some species are generalists and will blood-feed on a variety of vertebrate hosts, whereas others display marked host preference. Anopheles gambiae and Aedes aegypti have evolved a strong preference for humans, making them dangerously efficient vectors of malaria and Dengue haemorrhagic fever. Specific host odours probably drive this strong preference because other attractive cues, including body heat and exhaled carbon dioxide (CO2), are common to all warm-blooded hosts. Insects sense odours via several chemosensory receptor families, including the odorant receptors (ORs), membrane proteins that form heteromeric odour-gated ion channels comprising a variable ligand-selective subunit and an obligate co-receptor called Orco (ref. 6). Here we use zinc-finger nucleases to generate targeted mutations in the orco gene of A. aegypti to examine the contribution of Orco and the odorant receptor pathway to mosquito host selection and sensitivity to the insect repellent DEET (N,N-diethyl-meta-toluamide). orco mutant olfactory sensory neurons have greatly reduced spontaneous activity and lack odour-evoked responses. Behaviourally, orco mutant mosquitoes have severely reduced attraction to honey, an odour cue related to floral nectar, and do not respond to human scent in the absence of CO2. However, in the presence of CO2, female orco mutant mosquitoes retain strong attraction to both human and animal hosts, but no longer strongly prefer humans. orco mutant females are attracted to human hosts even in the presence of DEET, but are repelled upon contact, indicating that olfactory- and contact-mediated effects of DEET are mechanistically distinct. We conclude that the odorant receptor pathway is crucial for an anthropophilic vector mosquito to discriminate human from non-human hosts and to be effectively repelled by volatile DEET.

Longitudinal monitoring of anti-saliva antibodies as markers of repellent efficacy against Phlebotomus perniciosus and Phlebotomus papatasi in dogs.

A 2-year longitudinal study of enzyme-linked immunosorbent assay (ELISA) antibodies against Phlebotomus perniciosus and Phlebotomus papatasi (Diptera: Psychodidae) sandfly saliva was performed in 32 Beagle dogs treated preventively with an imidacloprid-permethrin topical insecticide in an endemic area in Spain. Dogs were grouped into three sandfly exposure groups according to the time of inclusion in the study. Assays analysed immunoglobulin G (IgG) against salivary gland homogenates (SGH) of both species and recombinant P. papatasi rSP32 and P. perniciosus rSP03B proteins in serum. The dogs were participating in a Leishmania infantum (Kinetoplastida: Trypanosomatidae) vaccine trial and were experimentally infected with the parasite in the second year. No dog acquired natural L. infantum infections during the first year, but most developed anti-saliva antibodies, and median log-transformed optical densities (LODs) were seasonal, mimicking those of local sandflies. This indicates that the repellent efficacy of the insecticide used is below 100%. Multi-level modelling of LODs revealed variability among dogs, autocorrelation and differences according to the salivary antigen and the dog's age. However, dog seroprevalence, estimated using pre-exposure LODs as cut-offs, was relatively low. This, and the fact that dogs did not become naturally infected with L. infantum, would support the efficacy and usefulness of this imidacloprid-permethrin topical insecticide in canine leishmaniasis control.

Protective practices against tick bites in Denmark, Norway and Sweden: a questionnaire-based study.

BACKGROUND: Tick-borne infections are of emerging and increasing concern in the Scandinavian countries Denmark, Norway and Sweden. Only few studies have investigated protective practices against tick bites in the general population. The aim of this multi-country study was to assess the use of protective practices and the perception of the efficacy of them. METHODS: We surveyed the extent of using protective practices against tick bites, using the same questionnaire in three local languages. In addition, we surveyed perceptions of how good a protection the different practices provide. Altogether 783 individuals from Denmark, 789 from Norway and 1096 from Sweden participated in the study by completing an extensive online questionnaire in October 2016. RESULTS: Altogether 1011 respondents (37.9%) reported using at least three different protective practices either often or always when in areas where there are ticks, while 522 (19.6%) reported using none. Female gender was among the factors identified as positively associated with using several of the specific practices often or always when in areas where there are ticks. The gender-difference in extent of using protective practices against tick bites was particularly pronounced in Sweden. Based on a multivariable logistic regression model, being female, being from Sweden, and having experienced one or more tick bites were positively associated with using at least three different protective practices against tick bites either often or always when in areas where there are ticks (odds ratios 1.90, 1.87 and 1.88, respectively). CONCLUSIONS: The results of our study, especially the observed differences by country and by gender, can be useful in targeting future information to the public. In particular, our results suggest that men across all ages should be considered a specific target group for this information.

Insecticidal and repellent properties of novel trifluoromethylphenyl amides III.

The adulticidal, larvicidal, and repellent activity of 18 trifluoromethylphenyl amides (TFMPAs) was determined against Aedes aegypti mosquitoes. The compounds studied are the third generation designed from active structures of the previous two generations. N-(3,5-Bis(trifluoromethyl)phenyl)-2-chloroacetamide (8f) and N-(3,5-bis(trifluoromethyl)phenyl)-2,2,3,3,3-pentafluoropropanamide (8h) were most active against 1st stage Ae. aegypti larvae with LC50 values of 125 and 2.53 µM; for comparative purposes, the published LC50 for fipronil is 0.014 µM. Compound 8h was the most toxic against adult female Ae. aegypti with an LD50 = 2.12 nmol/mg, followed by 8f, and N-(3,5-bis(trifluoromethyl)phenyl)-2,2,2-trifluoroacetamide (8g) with LD50 values of 4.27 and 4.73 nmol/mg, respectively, although these compounds were significantly less toxic than fipronil against adult female Ae. aegypti. Compounds N-(2-(trifluoromethyl)phenyl)butyramide (9c), N-(2-(trifluoromethyl)phenyl)pentanamide (9d) and N-(2-(trifluoromethyl)phenyl)hex-5-enamide (9e) were the best repellents for female Ae. aegypti, with minimum effective dosages (MEDs) of 0.026, 0.052, and 0.091 µmol/cm2, respectively, compared to DEET at 0.052 µmol/cm2. Out of 52 TFMPAs (total number of compounds from three generations of this research) compound 9c was the most active repellent along with two synthesized in our previous studies, 2-chloro-N-(3-(trifluoromethyl)phenyl)acetamide (6a) and 2,2,2-trifluoro-N-(2-(trifluoromethyl)phenyl)acetamide (4c).

Use of mosquito repellents to protect against Zika virus infection among pregnant women in Brazil.

OBJECTIVES: To evaluate the use of repellents among pregnant women as a protective measure against infection with the Zika virus. STUDY DESIGN: Pregnant women (n = 177) were interviewed between November 2016 and February 2017 at Basic Health Units in the city of Propriá, state of Sergipe, Brazil. Two units were located in rural areas and eight in urban regions. METHODS: Data were analysed using descriptive statistical methods, the Chi-squared test or Fisher's exact test and odds ratios. The independent variables were grouped by analysis of the main components, and adherence to the use of the repellent was analysed by the logistic regression method. RESULTS: A total of 100 women reported using repellents at the time of the interview (56%). The use of repellents was greater among women with higher levels of education (83%) than those with only high school (68%) or elementary school (36%) education. Women assisted by the income transfer programme (Bolsa Família) presented a 2.27 times greater chance of not using repellents compared with pregnant women who were not receiving benefits of the programme. Regarding the logistic regression model, we observed that low economic and social conditions of pregnant women, as well as their lack of advice, had a negative effect on the use of repellents. CONCLUSIONS: Repellents were generally used as a preventive measure in pregnant women with higher levels of schooling and fewer children. The relatively high cost of repellents was the main reason for non-use.

Oxidative stress and neuromodulatory effects of deltamethrin and its combination with insect repellents in rats.

Deltamethrin (DEL) and other synthetic repellents like N,N-diethyl benzamide (DEB), N,N-diethyl phenylacetamide (DEPA), and N,N-diethyl meta toluamide (DEET) are widely used due their high efficacy against mosquitoes. We evaluated the safe dose on exposure to insecticide and insect repellent individually and in combination in Wistar rats. Rats were administrated with individual chemicals DEL, DEB, DEPA, and DEET and in combination of DEL along DEB, DEPA, and DEET. The reduced glutathione and its detoxifying enzymes were significantly increased in DEL treated rats. Serotonin, dopamine, and noradrenaline were increased in DEL alone and its combination groups. Histopathology revealed that DEL and along with other insect repellants can cause lung toxicities. This study suggests that DEL in combination with other insect repellents showed antagonistic effect against oxidative stress, and there was no significant toxicological effect in the combination groups. The insect repellents with DEL cause less toxic effect and is safe for use.

Community perception and risk reduction practices toward malaria and dengue: A mixed-method study in slums of Chetla, Kolkata.

BACKGROUND: Globally, vector-borne diseases account for 17% of infectious disease burden. In India, despite accelerated efforts, both malaria and dengue are major public health concern. Understanding local community perspectives is essential to strengthen ongoing program activities. OBJECTIVES: The study aimed to assess the community perceptions and risk reduction practices toward prevention and control of malaria and dengue at slums of Chetla in South Kolkata and to explore the perspectives of relevant local stakeholders in this regard. METHODS: This cross-sectional study with mixed-method design was conducted from June to September 2018. Quantitative data were collected in 288 sampled households through face-to-face interview of respondents and environmental checklist, whereas, qualitative exploration was done with five key informant interviews. Quantitative data were analyzed using SPSS version 16 Software. Qualitative data were analyzed thematically using "cut and sort" processing technique. RESULTS: In household survey, majority had unsatisfactory knowledge (68.4%), attitude (64.2%), and practices (62.8%) regarding diseases prevention/control, which was further substantiated by qualitative findings. The use of electric fans (79.5%), mosquito repellents (53.8%) were predominant practices; however, only a few used bed nets regularly (26.0%). Reportedly, "heat" and "poor ventilation" were key reasons behind reluctance to use bed nets. Multivariable regression analysis revealed that increasing age, proximity to a nearby canal, and unsatisfactory knowledge significantly predicted unfavorable attitude, whereas, respondents' gender and unfavorable attitude significantly predicted poor practices. CONCLUSIONS: Intensified social behavior change communication with active community participation is the need of the hour to prevent malaria and dengue occurrence and future outbreaks.

Effectiveness of repellent delivered through village health volunteers on malaria incidence in villages in South-East Myanmar: a stepped-wedge cluster-randomised controlled trial protocol.

BACKGROUND: To combat emerging drug resistance in the Greater Mekong Sub-region (GMS) the World Health Organization and GMS countries have committed to eliminating malaria in the region by 2030. The overall approach includes providing universal access to diagnosis and treatment of malaria, and sustainable preventive measures, including vector control. Topical repellents are an intervention that can be used to target residual malaria transmission not covered by long lasting insecticide nets and indoor residual spraying. Although there is strong evidence that topical repellents protect against mosquito bites, evidence is not well established for the effectiveness of repellents distributed as part of malaria control activities in protecting against episodes of malaria. A common approach to deliver malaria services is to assign Village Health Volunteers (VHVs) to villages, particularly where limited or no services exist. The proposed trial aims to provide evidence for the effectiveness of repellent distributed through VHVs in reducing malaria. METHODS: The study is an open stepped-wedge cluster-randomised controlled trial randomised at the village level. Using this approach, repellent (N,N-diethyl-benzamide - 12% w/w, cream) is distributed by VHVs in villages sequentially throughout the malaria transmission season. Villages will be grouped into blocks, with blocks transitioned monthly from control (no repellent) to intervention states (to receive repellent) across 14 monthly intervals in random order). This follows a 4-week baseline period where all villages do not receive repellent. The primary endpoint is defined as the number of individuals positive for Plasmodium falciparum and Plasmodium vivax infections diagnosed by a rapid diagnostic test. Secondary endpoints include symptomatic malaria, Polymerase Chain Reaction (PCR)-detectable Plasmodium spp. infections, molecular markers of drug resistance and antibodies specific for Plasmodium spp. parasites. DISCUSSION: This study has been approved by relevant institutional ethics committees in Myanmar and Australia. Results will be disseminated through workshops, conferences and peer-reviewed publications. Findings will contribute to a better understanding of the optimal distribution mechanisms of repellent, context specific effectiveness and inform policy makers and implementers of malaria elimination programs in the GMS. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry ( ACTRN12616001434482 ). Retrospectively registered 14th October 2016.

Exploration of toxicological impacts following acute and sub-chronic exposure to ethyl anthranilate-loaded mosquito repellent patch.

In the recent years, growing concern about the potential toxicity of synthetic repellents has led to the development of environmentally safe non-toxic insect control methods. Present investigation explores the toxicological impacts of ethyl anthranilate-loaded mosquito repellent patch (EAMRP) on respiratory system following acute and sub-chronic inhalation exposure in Wistar rats. Lungs parameters such as enhanced pause, tidal volume, respiration rate, inspiration time, and expiration time were determined using whole body plethysmograph. X-ray, scanning electron microscopy and histology were utilized to study the morphology and microscopical architecture of lungs. Hematological and serum biochemical markers were estimated. Cytokines such as IL-1ß, IL-2, and IL-12 were also estimated in bronchoalveolar lavage fluid using ELISA kits. Finally, acute oral and dermal toxicity studies were carried out to study the accidental or intentional poisoning due to the ingestion and skin contact of EAMRP, respectively. The findings demonstrate that inhalation exposure to EAMRP did not pose any significant dose related toxicity in above mentioned experiments. Further, no appreciable toxicity was observed in both acute oral and dermal exposure. Thus, these results revealed the non toxic nature of EAMRP in preclinical studies. Hence, EAMRP can be used successfully as an alternative to existing synthetic repellents without any potential health hazards.

Acute inhalation toxicity study of n-heneicosane and its combination with diflubenzuron: An attracticide of Aedes aegypti.

OBJECTIVE: Combination of an oviposition pheromone and an insect growth regulator for the control of vectors is an effective approach. There is a need for toxicological evaluation before its introduction. The present study evaluates the acute inhalation toxicity of n-heneicosane and its combination with diflubenzuron in a head-only inhalation exposure chamber made of glass. MATERIALS AND METHODS: A head-only inhalation exposure chamber made of glass (volume: 3.5 l) was used for exposing four rats at a time. A glass nebulizer was used for aerosolization of n-heneicosane and its combination with diflubenzuron (1:10 w/w). Nebulization pressure was 10 and 15 psi and the air flow of exposure the chamber was adjusted to 30 lpm. Male Wistar rats were acclimatized in whole body plethysmographs that were connected to volumetric flow pressure transducers by silicon tubes. The transducers were connected to an amplifier and a digitized response was recorded through an oscillograph and personal computers. Respiratory variables were recorded online. After inhalation exposure, various other parameters like survival, body weight, organ body weight index and biochemical changes were recorded for analysis. RESULTS AND DISCUSSION: Particle size determination proved that the aerosol particles were within the respirable range. LC50 of n-heneicosane and its combination with diflubenzuron was found to be more than 5 g/m3. There were minimal changes observed during exposure to n-heneicosane and also its combination with diflubenzuron on the respiratory variables. The changes were not consistent with the dose. CONCLUSION: n-Heneicosane and its combination with diflubenzuron showed low mammalian toxicity.

DEET potentiates the development and persistence of anticholinesterase dependent chronic pain signs in a rat model of Gulf War Illness pain.

Exposure to DEET (N,N-diethyl-meta-toluamide) may have influenced the pattern of symptoms observed in soldiers with GWI (Gulf War Illness; Haley and Kurt, 1997). We examined how the addition of DEET (400mg/kg; 50% topical) to an exposure protocol of permethrin (2.6mg/kg; topical), chlorpyrifos (CP; 120mg/kg), and pyridostigmine bromide (PB;13mg/kg) altered the emergence and pattern of pain signs in an animal model of GWI pain (Nutter et al., 2015). Rats underwent behavioral testing before, during and after a 4week exposure: 1) hindlimb pressure withdrawal threshold; 2) ambulation (movement distance and rate); and 3) resting duration. Additional studies were conducted to assess the influence of acute DEET (10-100µM) on muscle and vascular nociceptor Kv7, KDR, Nav1.8 and Nav1.9. We report that a 50% concentration of DEET enhanced the development and persistence of pain-signs. Rats exposed to all 4 compounds exhibited ambulation deficits that appeared 5-12weeks post-exposure and persisted through weeks 21-24. Rats exposed to only three agents (CP or PB excluded), did not fully develop ambulation deficits. When PB was excluded, rats also developed rest duration pain signs, in addition to ambulation deficits. There was no evidence that physiological doses of DEET acutely modified nociceptor Kv7, KDR, Nav1.8 or Nav1.9 activities. Nevertheless, DEET augmented protocols decreased the conductance of Kv7 expressed in vascular nociceptors harvested from chronically exposed rats. We concluded that DEET enhanced the development and persistence of pain behaviors, but the anticholinesterases CP and PB played a determinant role.

Reported community-level indoor residual spray coverage from two-stage cluster surveys in sub-Saharan Africa.

BACKGROUND: Malaria is an important cause of morbidity and mortality in malaria-endemic areas. Indoor residual spray is an effective intervention to control malaria, but high community-level coverage is needed to maximize its impact. METHODS AND RESULTS: Using thirty-four two-stage cluster surveys (e.g., demographic and health surveys) and lot quality assurance sampling, indoor residual spray was estimated at the community level (i.e. enumeration-area) across sub-Saharan Africa since 2010. For communities receiving indoor residual spray a logistic regression predicted whether community-level coverage exceeded 50% or not. Household-level coverage was equitable both in terms of wealth and urban/rural, with poorer and rural houses more likely to be sprayed than richer and urban houses. Coverage of indoor residual spray at the community level is poor across the continent, with 54% of communities receiving the intervention not reaching 50% coverage. Having >50% coverage at the community-level was not associated with increasing the number of houses sprayed in the country. CONCLUSIONS: Implementation and monitoring of indoor residual coverage at small geographical scales need to improve greatly to receive maximum benefit of the intervention.

Development and characterization of repellent formulations based on nanostructured hydrogels.

Diseases caused by insects could lead to epidemic scenarios in urban areas and insect repellents are a shield against a wide range of insects, but they need to be safe without compromising efficacy. Ethyl butylacetylaminopropionate (EB) is a synthetic mosquito repellent, which could be used in products for adults and children due to its low-allergenic potential. The aim of this study was to develop and characterize EB and Poloxamer 407 nanoemulsions regarding their droplets mean size, pH, rheological properties, cytotoxicity and in vitro permeation profile. The developed formulations (F1 with 12.5% of EB and F2 with 25% of EB) were compared with a commercial formulation containing 12.5% of EB. Droplets mean size was determined by DLS, and for both nanoemulsions they were around 200 nm; however, the commercial formulation presented a droplets mean size of 10 nm, which could contribute to its high permeation. F1 and F2 presented a gel-like behavior, however F2 presented lower viscosity due to the presence of more EB between the polymer chains preventing them to interact with each other. Also, F2 was less retained by the epidermis when compared to F1 probably due to its lower viscosity. For the cytotoxicity assay only F2, which presented the highest concentration of EB was tested, and it was not toxic to the cells. This result could be also extended to F1 which presented half the EB concentration. The present study demonstrated that EB and Poloxamer 407 nanoemulsions are promising as new insect-repellent formulations.

Repellent effect of microencapsulated essential oil in lotion formulation against mosquito bites.

BACKGROUND & OBJECTIVES: Many essential oils have been reported as natural sources of insect repellents; however, due to high volatility, they present low repellent effect. Formulation technique by using microencapsulation enables to control the volatility of essential oil and thereby extends the duration of repellency. In this study, the effectiveness of microencapsulated essential oils of Alpinia galanga, Citrus grandis and C. aurantifolia in the lotion formulations were evaluated against mosquito bites. METHODS: Essential oils and N,N-Diethyl-3-methylbenzamide (DEET) were encapsulated by using interfacial pre- cipitation techniques before incorporation into lotion base to form microencapsulated (ME) formulation. The pure essential oil and DEET were also prepared into lotion base to produce non-encapsulated (NE) formulation. All the prepared formulations were assessed for their repellent activity against Culex quinquefasciatus under laboratory condition. Field evaluations also were conducted in three different study sites in Peninsular Malaysia. In addi- tion, Citriodiol® (Mosiquard®) and citronella-based repellents (KAPS®, MozAway® and BioZ Natural®) were also included for comparison. RESULTS: In laboratory conditions, the ME formulations of the essential oils showed no significant difference with regard to the duration of repellent effect compared to the microencapsulated DEET used at the highest con- centration (20%). It exhibited >98% repellent effect for duration of 4 h (p = 0.06). In the field conditions, these formulations demonstrated comparable repellent effect (100% for a duration of 3 h) to Citriodiol® based repellent (Mosiguard®) (p = 0.07). In both test conditions, the ME formulations of the essential oils presented longer duration of 100% repellent effect (between 1 and 2 h) compared to NE formulations. INTERPRETATION & CONCLUSION: The findings of the study demonstrate that the application of the microencapsulation technique during the preparation of the formulations significantly increases the duration of the repellent effect of the essential oils, suggesting that the ME formulation of essential oils have potential to be commercialized as an alternative plant-based repellent in the market against the mosquitoes.

Application of mosquito repellent coils and associated self-reported health issues in Ghana.

BACKGROUND: The use of mosquito coils has gained widespread patronage in malaria-endemic countries, even though it is not a recommended preventive measure for avoiding mosquitoes. Mosquito coils contain insecticides, which are expected to vaporize slowly once the coil is lit, to provide protection against the mosquito. The mosquito coil base material contains a variety of compounds capable of burning slowly to gradually release the insecticide. The mosquito coil smoke, however, is potentially a source of indoor air pollution with implications for acute respiratory infections (ARI) and other illnesses. The present study investigated the application of mosquito coils and associated self-reported health issues in Ghana. METHODS: A cross-sectional study was undertaken in which questionnaires were randomly administered to 480 households across four districts in Ghana. Respondents who exclusively applied mosquito coils were grouped as test cohort, while those who did not apply any mosquito repellency method constituted a control cohort. RESULTS: The test group that applied mosquito coils reported malaria incidence rate of 86.3 %. The control group that did not apply any mosquito repellency method reported an incidence rate of malaria at 72.4 %. Chi square analysis suggested that the observed difference was statistically significant (x (2) = 4.25; p = 0.04). The number of respondents who reported symptoms of cough from mosquito coil application (52.6 % incidence rate) was marginally greater than their counterparts who did not apply coils (46.1 % incidence rate). It was also found that respondents with shortage of breath, which was used as a proxy for ARI, were more likely to have applied mosquito coil. CONCLUSIONS: The application of mosquito coils did not necessarily reduce the incidence of malaria in the study communities. It however presented a potential respiratory risk factor, which should be further investigated by critically examining exposure to particulate matter emissions from burning coils.

The Use of Microdispensers with Spatial Repellents for Personal Protection Against Mosquito Biting.

Mosquito-borne pathogens affect millions of people worldwide. This work describes a new method to deliver spatial repellents. Functional microdispensers (FMDs) were designed to deliver spatial repellents against mosquitoes. In vivo trials showed that FMDs protect human subjects against mosquitoes by reducing 70­90% of bites received, with a protection that lasted up to 4 weeks. FMDs can be cost-effectively implemented as wearable or field-dispensed devices for local area protection, defined as a confined geographical region.

OFF! Clip-on Repellent Device With Metofluthrin Tested on Aedes aegypti (Diptera: Culicidae) for Mortality at Different Time Intervals and Distances.

The OFF! Clip-on mosquito-repellent device was tested outdoors against Aedes aegypti (L.). A single treatment device was used against batches of caged adult, nonblood fed Ae. aegypti at multiple locations 0.3m from treatment center. Another set of cages was stationed 0.6m from treatment. A final set of cages was placed 0.9m away. Trials ran for durations of 5, 15, 30, and 60 min. Initial knockdown and mortality after 24 h was recorded. The devices had effective knockdown and mortality. This was not sustained at distances greater than 0.3m from the device.