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Aedes aegypti and Aedes albopictus are invasive mosquito species with geographic ranges that have oscillated within Florida since their presence was first documented. Local transmission of dengue, chikungunya, and Zika viruses serves as evidence of the public health importance of these two species. It is important to have detailed knowledge of their distribution to aid in mosquito control efforts and understand the risk of arbovirus transmission to humans. Through a partnership involving the University of Florida Institute of Food and Agricultural Sciences Cooperative Extension Service and the Florida Medical Entomology Laboratory; the Florida Department of Health; and mosquito control agencies throughout Florida, a container mosquito surveillance program involving all life stages was launched in the summer of 2016 to detect the presence of Ae. aegypti and Ae. albopictus. Results from this survey were mapped to provide a picture of the current known distribution of Ae. aegypti and Ae. albopictus in Florida. Aedes aegypti and/or Ae. albopictus were detected in the 56 counties that were part of the survey. Only Aedes albopictus was detected in 26 counties, primarily in the panhandle region of Florida. The results of this work underscore the importance of maintaining container mosquito surveillance in a state where chikungunya, dengue, and Zika viruses are present and where there is continued risk for exotic arbovirus introductions.
Monitoring mosquito populations is essential to designing and implementing control strategies. Recent strategies based on releasing biologically modified mosquitoes have increased the need to effectively monitor mosquito abundance. Unfortunately, existing surveillance traps are of limited value due to their high cost and low capture rates. Here, we report the results of experiments designed to evaluate the effectiveness of an acoustic trap prototype. Stimuli synthesized from recordings of Ae. aegypti wingbeat signals and pure tones were evaluated as attractants to males in indoor and semi-field conditions. Overall, the acoustic trap's efficacy differed significantly between indoor and semi-field conditions. After two hours of indoor recapture, ∼69% of males were collected from acoustic traps broadcasting pure tones while ∼78% of males were collected using synthesized wingbeat signals. Under semi-field conditions, however, acoustic traps collected less than ∼1.7% of the males released. Increasing the intensity of the signals up to 90 dB (SPL re. 20 uPa at 1 m from the trap) did not improve the capture rate under semi-field conditions. Overall, our results indicate that acoustic signals synthesized from recordings of wingbeats can be used to enhance capture of male Ae. aegypti.
In order to elucidate the poorly understood relationships between mosquito larvae and their predatory aquatic insects in urban and suburban areas of tropical Southeast Asia, where vector-borne diseases are prevalent, aquatic insects were sampled from 14 aquatic habitats in residential areas of Chiang Mai, northern Thailand, during the rainy season (July to November) in 2016. Correlations among biological variables, densities of major predatory aquatic insect groups (i.e., Odonata, Coleoptera, and Hemiptera: OCH group) in wetlands and artificial lentic habitats, and the density of mosquito larvae were analyzed. Among the sampled mosquito larvae, Culex spp. were the most abundant, and both OCH density and water quality were major determinants of Culex spp. density (rs = -0.302 and -0.396, respectively). Logistic regression analyses indicated that the probability of Culex spp. occurrence was significantly and negatively correlated with OCH density. Furthermore, high macrophyte abundance was associated with higher predator density, potentially reducing mosquito density. Hemipteran predators were most negatively correlated with Culex spp. density, regardless of whether macrophyte abundance was high or low (rs = -0.547 and -0.533, respectively). Therefore, hemipteran predators were the most important aquatic insect predators in the urban and suburban residential areas of Chiang Mai, Thailand, and OCH species, such as the hemipteran Micronecta scutellaris, could be used as biological control agents against mosquitoes in the region.
Pâmela dos Santos Andrade, Paulo Roberto Urbinatti, Ronan da Rocha Coelho, Rosa Maria Marques de Sá Almeida, Sabrina Santana Ribeiro, Tamara Nunes de Lima-Camara
The objective of this study was to assess the parity, presence of blood in the stomach, and the gonotrophic discordance of females of Aedes aegypti and Aedes albopictus captured in two areas of the city of São Paulo. The captures were undertaken monthly, by aspiration, in the period from January, 2015 to August, 2017. All the females of the two species had their midguts and ovaries dissected to determine the presence of blood and the parity/stage of maturation. With regard to parity, 27% and 34% of the females of Ae. aegypti and Ae. albopictus, respectively, were parous or were in advanced stages of the development of their ovaries (33% and 27%, respectively). The larger part of the females of Ae. aegypti and Ae. albopictus contained blood in their stomachs (77% and 60%, respectively), beyond which 36% and 27% of the females of Ae. aegypti and Ae. albopictus, respectively, were in gonotrophic discordance. Our results indicate favorable conditions in the study areas because of the presence of parous females. Moreover, this frequent and multiple contact of Ae. aegypti and Ae. albopictus females with vertebrate hosts, such as humans, increases the possibility of transmitting the viruses they may be carrying.
Some limnic copepod species are predators of mosquito larvae. Seven species belonging to the order Cyclopoida, family Cyclopidae, were collected in the field in Germany and tested for the first time in laboratory bioassays for their potential to serve as biological control agents of the invasive Asian bush mosquito Aedes japonicus (Theobald), a vector of various pathogens causing disease. Females of Diacyclops bicuspidatus (Claus) did not attack 1st instar larvae of Ae. japonicus, but Macrocyclops distinctus (Richard), Cyclops divergens Lindberg, and C. heberti Einsle predated a mean of 14, 18, or 19 1st instar larvae, respectively. Acanthocyclops einslei Mirabdullayev and Defaye killed 30 larvae, and high predation rates with a mean of 39 or 46 larvae, respectively, were obtained by Megacyclops viridis (Jurine) and M. gigas (Claus). In regression analyses, predation rates by M. viridis correlated with body size, with specimens of 1.8 mm length being more effective than smaller or bigger ones. Based on the presented data, the two Megacyclops species seem to be promising candidates for use in field studies on the biological control of Ae. japonicus.
In 2008, an outbreak of yellow fever occurred in Abidjan. The entomological investigations confirm that Abidjan is at risk of yellow fever with a suspicion of the National Park of Banco (NPB) forest as a likely area of re-emergence. This study aims to assess the dispersion of sylvatic vectors of arboviruses from the NPB forest to the surrounding areas (Andokoi and Sagbé). The sampling was done in the rainy season using the WHO layer-traps technique. Among the six species of Aedes sampled, Aedes aegypti and Aedes africanus were the potential vectors of arboviruses. Both species were collected in Sagbé but only Ae. aegypti in Andokoi. Only Ae. aegypti were present 400 and 800 m from NPB forest, but at 200 m, it showed respective proportions of 75.5% and 87.5% in Sagbé and Andokoi. In the NPB forest, however, Ae. africanus has been the predominant species. The study showed the presence of Ae. aegypti in Andokoi and Sagbé. However, Ae. africanus was found in the NPB forest and in the 200 m radius in Sagbé. The establishment of an entomological surveillance program in all areas would therefore be essential for the prevention of arboviruses outbreaks in Abidjan.
House flies are global pests and notoriously difficult to control. Essential oils of vetiver, cinnamon, and lavender and their blends were tested for toxic and repellent effects against larval and adult flies. All of the oils had moderate toxicity for eggs. Mortality of 2nd instar larvae was 57–78% in dipping assays, 38–100% in contact assays, and 94–100% in treated media. Lavender was less effective (38% mortality) than the others (91–100%) in contact bioassays. Oil blends were not more effective against larvae than individual oils. Vetiver and cinnamon oils were strongly repellent (84 and 78%, respectively) for larvae in treated media. None of the oils were repellent for adult house flies in olfactometer assays, but testing of additional products demonstrated significant repellency for neem oil, p-menthane-3,8-diol (PMD), and vanillin. Contact/fumigant toxicity of vetiver, cinnamon, and lavender oils was 100%, significantly higher than mortality from sunflower oil (67%). Blends of oils were not more effective against adults than the individual oils, but blends diluted with sunflower oil were as effective as the individual oils. Essentials oils of vetiver and cinnamon may have potential for fly management in situations where conventional insecticides cannot be used.
Urbanization has caused an increase in favorable habitats for Aedes aegypti (Diptera: Culicidae), given their ability to reproduce in small and often non-degradable artificial water-containers. While much work has been done on Ae. aegypti biology and ecology in urban landscapes, the role of shading on immature stages as an independent factor from temperature, and any possible interactions between these factors, remains unexamined. We assessed how temperature and shading affected egg hatch-rate, larval/pupal mortality, and larval development to adult stage under different factorial temperature (28; 31; 34; 37; 40° C) and shade (0%, 3,100 lux; 40%, 1,860 lux; 75%, 775 lux; 100%, 0 lux) regimes. Hatch-rate was significantly lower at 37° C (57 %), and no eggs hatched at 40° C. There was no significant effect caused by shading on hatchability. Larval and pupal mortality at 37° C was significantly higher (35%) compared to lower temperature groups, while the effects of shading were emergent at low temperatures. Developmental times from hatching to adult emergence were significantly reduced with increasing temperatures and with greater light exposures. The eco-physiological response of Ae. aegypti larvae to temperature and light regimes suggest a photosensitivity previously unstudied in this species.
Marie Paul Audrey Mayi, David Forfuet Foncha, Cyril Kowo, Timoleon Tchuinkam, Katherine Brisco, Damian Nota Anong, Sehgal Ravinder, Anthony John Cornel
Deforestation is a major threat to biodiversity but little data exist on how deforestation in real-time affects the overall mosquito species community despite its known role in the transmission of diseases. We compared the abundance and diversity of Culex mosquitoes before and after deforestation along a gradient of three different anthropogenic disturbance levels in a tropical rainforest in southwestern Cameroon. The collections were conducted in unlogged forest (January, 2016), selectively logged forest (January, 2017), and within a young palm plantation (October, 2017) using net traps, sweep nets, resting traps, and dipping for immature stages in water bodies. Mosquitoes were morphologically identified to subspecies, groups, and species. A total of 2,556 mosquitoes was collected of which 1,663 (65.06%) belong to the genus Culex, (n=427 (25.68%) in the unlogged forest; n=900 (54.12%) in the selectively logged forest; and n=336 (20.2%) in the young palm plantation) with a significant difference among the habitats. Diversity and richness of mosquitoes varied significantly among habitats with the highest values found in the selectively logged forest (H=2.4; DS=0.87; S=33) and the lowest value in the unlogged forest (H=1.37; DS=0.68; S=13). The results of this study showed that deforestation affects the abundance and diversity of Culex mosquitoes and favors the invasion of anthropophilic mosquitoes. Higher mosquito abundance and diversity in the selectively logged forest than in the pristine forest is notable and some explanations for these differences are discussed.
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