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Concept: DEET


Reducing the number of host-vector interactions is an effective way to reduce the spread of vector-borne diseases. Repellents are widely used to protect humans from a variety of protozoans, viruses, and nematodes. DEET (N,N-Diethyl-meta-toluamide), a safe and effective repellent, was developed during World War II. Fear of possible side effects of DEET has created a large market for “natural” DEET-free repellents with a variety of active ingredients. We present a comparative study on the efficacy of eight commercially available products, two fragrances, and a vitamin B patch. The products were tested using a human hand as attractant in a Y-tube olfactometer setup with Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse), both major human disease vectors. We found that Ae. albopictus were generally less attracted to the test subject’s hand compared with Ae, aegypti. Repellents with DEET as active ingredient had a prominent repellency effect over longer times and on both species. Repellents containing p-menthane-3,8-diol produced comparable results but for shorter time periods. Some of the DEET-free products containing citronella or geraniol did not have any significant repellency effect. Interestingly, the perfume we tested had a modest repellency effect early after application, and the vitamin B patch had no effect on either species. This study shows that the different active ingredients in commercially available mosquito repellent products are not equivalent in terms of duration and strength of repellency. Our results suggest that products containing DEET or p-menthane-3,8-diol have long-lasting repellent effects and therefore provide good protection from mosquito-borne diseases.

Concepts: Effectiveness, Mosquito, Aedes aegypti, Aedes, Dengue fever, Insect repellent, Asian tiger mosquito, DEET


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.

Concepts: Malaria, Mosquito, Australia, Dengue fever, West Nile virus, Insect repellent, DEET, New South Wales


Mosquito feeding behaviour determines the degree of vector-host contact and may have a serious impact on the risk of West Nile virus (WNV) epidemics. Feeding behaviour also interacts with other biotic and abiotic factors that affect virus amplification and transmission.

Concepts: Mosquito, Ribavirin, Dengue fever, Mosquito control, West Nile virus, DEET, Biotic component, Abiotic component


Abstract. Entomologic investigations were conducted during an intense outbreak of West Nile virus (WNV) disease in Maricopa County, Arizona during July 31-August 9, 2010. The investigations compared the East Valley outbreak area, and a demographically similar control area in northwestern metropolitan Phoenix where no human cases were reported. Five mosquito species were identified in each area, and species composition was similar in both areas. Significantly more Culex quinquefasciatus females were collected by gravid traps at Outbreak sites (22.2 per trap night) than at control sites (8.9 per trap night), indicating higher Cx. quinquefasciatus abundance in the outbreak area. Twenty-eight WNV TaqMan reverse transcription-polymerase chain reaction-positive mosquito pools were identified, including 24 of Cx. quinquefasciatus, 3 of Psorophora columbiae, and 1 of Culex sp. However, Cx. quinquefasciatus WNV infection rates did not differ between outbreak and control sites. At outbreak sites, 30 of 39 engorged Cx. quinquefasciatus had fed on birds, 8 of 39 on humans, and 1 of 39 on a lizard. At control sites, 20 of 20 identified blood meals were from birds. Data suggest that Cx. quinquefasciatus was the primary enzootic and epidemic vector of this outbreak. The most important parameters in the outbreak were vector abundance and blood meal analysis, which suggested more frequent contact between Cx. quinquefasciatus and human hosts in the outbreak area compared with the control area.

Concepts: Epidemiology, Mosquito, Dengue fever, West Nile virus, Centers for Disease Control and Prevention, DEET, Arizona, Phoenix, Arizona


Mosquitoes in the Culex pipiens complex are considered to be involved in the transmission of a range of pathogens, including West Nile virus (WNV). Although its taxonomic status is still debated, the complex includes species, both globally distributed or with a more limited distribution, morphologically similar and characterised by different physiological and behavioural traits, which affect their ability as vectors. In many European countries, Cx. pipiens and its sibling species Culex torrentium occur in sympatry, exhibiting similar bionomic and morphological characters, but only Cx. pipiens appears to play a vector role in WNV transmission. This species consists of two biotypes, pipiens and molestus, which can interbreed when in sympatry, and their hybrids can act as WNV-bridge vectors, due to intermediate ecological features. Considering the yearly WNV outbreaks since 2008 and given the morphological difficulties in recognising species and biotypes, our aim was to molecularly identify and characterised Cx. pipiens and Cx. torrentium in Italy, using recently developed molecular assays. Culex torrentium was not detected; as in other European countries, the pipiens and molestus biotypes were widely found in sympatry with hybrids in most environments. The UPGMA cluster analysis applied to CQ11 genotypic frequencies mainly revealed two groups of Cx. pipiens populations that differed in ecological features. The high propensity of the molestus biotype to exist in hypogean environments, where the habitat’s physical characteristics hinder and preclude the gene flow, was shown. These results confirmed the CQ11 assay as a reliable diagnostic method, consistent with the ecological and physiological aspects of the populations analysed. Since the assessment of the actual role of three biotypes in the WNV circulation remains a crucial point to be elucidated, this extensive molecular screening of Cx. pipiens populations can provide new insights into the ecology of the species and may give useful indications to plan and implement WNV surveillance activities in Italy.

Concepts: Gene, Evolution, Biology, Mosquito, Assay, West Nile virus, Centers for Disease Control and Prevention, DEET


Although Zika virus (ZIKV) infection in pregnant women can cause placental damage, intrauterine growth restriction, microcephaly, and fetal demise, these disease manifestations only became apparent in the context of a large epidemic in the Americas. We hypothesized that ZIKV is not unique among arboviruses in its ability to cause congenital infection. To evaluate this, we tested the capacity of four emerging arboviruses [West Nile virus (WNV), Powassan virus (POWV), chikungunya virus (CHIKV), and Mayaro virus (MAYV)] from related (flavivirus) and unrelated (alphavirus) genera to infect the placenta and fetus in immunocompetent, wild-type mice. Although all four viruses caused placental infection, only infection with the neurotropic flaviviruses (WNV and POWV) resulted in fetal demise. WNV and POWV also replicated efficiently in second-trimester human maternal (decidua) and fetal (chorionic villi and fetal membrane) explants, whereas CHIKV and MAYV replicated less efficiently. In mice, RNA in situ hybridization and histopathological analysis revealed that WNV infected the placenta and fetal central nervous system, causing injury to the developing brain. In comparison, CHIKV and MAYV did not cause substantive placental or fetal damage despite evidence of vertical transmission. On the basis of the susceptibility of human maternal and fetal tissue explants and pathogenesis experiments in immunocompetent mice, other emerging neurotropic flaviviruses may share with ZIKV the capacity for transplacental transmission, as well as subsequent infection and injury to the developing fetus.

Concepts: Pregnancy, Fetus, Virus, Infection, Placenta, Flavivirus, Flaviviruses, DEET


A sensitive and robust method using solid-phase extraction and ultrasonic extraction for preconcentration followed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS-MS) has been developed for determination of 19 biocides: eight azole fungicides (climbazole, clotrimazole, ketoconazole, miconazole, fluconazole, itraconazole, thiabendazole, and carbendazim), two insect repellents (N,N-diethyl-3-methylbenzamide (DEET), and icaridin (also known as picaridin)), three isothiazolinone antifouling agents (1,2-benzisothiazolinone (BIT), 2-n-octyl-4-isothiazolinone (OIT), and 4,5-dichloro-2-n-octyl-isothiazolinone (DCOIT)), four paraben preservatives (methylparaben, ethylparaben, propylparaben, and butylparaben), and two disinfectants (triclosan and triclocarban) in surface water, wastewater, sediment, sludge, and soil. Recovery of the target compounds from surface water, influent, effluent, sediment, sludge, and soil was mostly in the range 70-120 %, with corresponding method quantification limits ranging from 0.01 to 0.31 ng L(-1), 0.07 to 7.48 ng L(-1), 0.01 to 3.90 ng L(-1), 0.01 to 0.45 ng g(-1), 0.01 to 6.37 ng g(-1), and 0.01 to 0.73 ng g(-1), respectively. Carbendazim, climbazole, clotrimazole, methylparaben, miconazole, triclocarban, and triclosan were detected at low ng L(-1) (or ng g(-1)) levels in surface water, sediment, and sludge-amended soil. Fifteen target compounds were found in influent samples, at concentrations ranging between 0.4 (thiabendazole) and 372 ng L(-1) (methylparaben). Fifteen target compounds were found in effluent samples, at concentrations ranging between 0.4 (thiabendazole) and 114 ng L(-1) (carbendazim). Ten target compounds were found in dewatered sludge samples, at concentrations ranging between 1.1 (DEET) and 887 ng g(-1) (triclocarban).

Concepts: Water, Liquid chromatography-mass spectrometry, Insect repellent, Paraben, Butylparaben, DEET, Icaridin, Ethylparaben


Since Zika virus (ZIKV) was detected in Brazil in 2015, it has spread explosively across the Americas and has been linked to increased incidence of microcephaly and Guillain-Barré syndrome (GBS). In one year, it has infected over 500,000 people (suspected and confirmed cases) in 40 countries and territories in the Americas. Along with recent epidemics of dengue (DENV) and chikungunya virus (CHIKV), which are also transmitted by Aedes aegypti and Ae. albopictus mosquitoes, the emergence of ZIKV suggests an ongoing intensification of environmental and social factors that have given rise to a new regime of arbovirus transmission. Here, we review hypotheses and preliminary evidence for the environmental and social changes that have fueled the ZIKV epidemic. Potential drivers include climate variation, land use change, poverty, and human movement. Beyond the direct impact of microcephaly and GBS, the ZIKV epidemic will likely have social ramifications for women’s health and economic consequences for tourism and beyond.

Concepts: Epidemiology, Mosquito, Chikungunya, Aedes aegypti, Aedes, Dengue fever, Mosquito control, DEET


West Nile virus (WNV) and Flanders virus (FLAV) co-occur in regions of North America. Because both viruses are maintained in a transmission cycle involving Culex mosquitoes and birds, screening mosquitoes for FLAV has been suggested as an enhancement to WNV surveillance and epidemic prediction. Using samples collected in 2010 and 2012 in Chicago, IL, USA, we demonstrate the presence of FLAV in four out of 287 (1.4%) Culex pools. We estimated minimum infection rates for WNV and FLAV to be 5.66 and 1.22 in 2010 and 8.74 and 0.61 in 2012, respectively. FLAV occurred 1 and 3 wk prior to the peak of WNV transmission in 2010 and 2012, respectively. FLAV sequences from Chicago were genetically diverse and phylogenetically representative of lineage A viruses from across the United States.

Concepts: United States, Mosquito, Ribavirin, Viruses, Dengue fever, Mosquito control, West Nile virus, DEET


West Nile virus (WNV) is now endemic in the continental United States; however, our ability to predict spillover transmission risk and human WNV cases remains limited. Here we develop a model depicting WNV transmission dynamics, which we optimize using a data assimilation method and two observed data streams, mosquito infection rates and reported human WNV cases. The coupled model-inference framework is then used to generate retrospective ensemble forecasts of historical WNV outbreaks in Long Island, New York for 2001-2014. Accurate forecasts of mosquito infection rates are generated before peak infection, and >65% of forecasts accurately predict seasonal total human WNV cases up to 9 weeks before the past reported case. This work provides the foundation for implementation of a statistically rigorous system for real-time forecast of seasonal outbreaks of WNV.

Concepts: Mosquito, Future, Ribavirin, Dengue fever, Forecasting, Mosquito control, West Nile virus, DEET