Aedes aegypti oviposition-sites choice under semi-field conditions.
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ABSTRACT:
SUBMITTER: David MR
PROVIDER: S-EPMC10946600 | biostudies-literature | 2023 Dec
REPOSITORIES: biostudies-literature
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Aedes aegypti oviposition-sites choice under semi-field conditions.
David Mariana R MR Maciel-de-Freitas Rafael R Petersen Martha T MT Bray Daniel D Hawkes Frances M FM Fernández-Grandon G Mandela GM Young Stephen S Gibson Gabriella G Hopkins Richard J RJ
Medical and veterinary entomology 20230602 4
Vector control is still the recommended approach to avoid arbovirus outbreaks. Herein, we investigate oviposition preferences of Aedes aegypti (Diptera: Culicidae) females under a semi-field structure Rio de Janeiro, Brazil. For that, in Experiment 1, we used two settings: 'Single items', which included as containers drain, beer bottle, bucket, car tyre, water tank, and a potted Peace Lily (Spathiphyllum wallisii) in a saucer with water, or 'Multiple containers', as an urban simulation, in which ...[more]
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Project description:Wolbachia bacteria are now being introduced into Aedes aegypti mosquito populations for dengue control. When Wolbachia infections are at a high frequency, they influence the local transmission of dengue by direct virus blocking as well as deleterious effects on vector mosquito populations. However, the effectiveness of this strategy could be influenced by environmental temperatures that decrease Wolbachia density, thereby reducing the ability of Wolbachia to invade and persist in the population and block viruses. We reared wMel-infected Ae. aegypti larvae in the field during the wet season in Cairns, North Queensland. Containers placed in the shade produced mosquitoes with a high Wolbachia density and little impact on cytoplasmic incompatibility. However, in 50% shade where temperatures reached 39°C during the day, wMel-infected males partially lost their ability to induce cytoplasmic incompatibility and females had greatly reduced egg hatch when crossed to infected males. In a second experiment under somewhat hotter conditions (>40°C in 50% shade), field-reared wMel-infected females had their egg hatch reduced to 25% when crossed to field-reared wMel-infected males. Wolbachia density was reduced in 50% shade for both sexes in both experiments, with some mosquitoes cleared of their Wolbachia infections entirely. To investigate the critical temperature range for the loss of Wolbachia infections, we held Ae. aegypti eggs in thermocyclers for one week at a range of cyclical temperatures. Adult wMel density declined when eggs were held at 26-36°C or above with complete loss at 30-40°C, while the density of wAlbB remained high until temperatures were lethal. These findings suggest that high temperature effects on Wolbachia are potentially substantial when breeding containers are exposed to partial sunlight but not shade. Heat stress could reduce the ability of Wolbachia infections to invade mosquito populations in some locations and may compromise the ability of Wolbachia to block virus transmission in the field. Temperature effects may also have an ecological impact on mosquito populations given that a proportion of the population becomes self-incompatible.
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Project description:BackgroundNew contained semi-field cages are being developed and used to test novel vector control strategies of dengue and malaria vectors. We herein describe a new Quarantine Insectary Level-2 (QIC-2) laboratory and field cages (James Cook University Mosquito Research Facility Semi-Field System; MRF SFS) that are being used to measure the impact of the endosymbiont Wolbachia pipientis on populations of Aedes aegypti in Cairns Australia.Methodology/principal findingsThe MRF consists of a single QIC-2 laboratory/insectary that connects through a central corridor to two identical QIC-2 semi-field cages. The semi-field cages are constructed of two layers of 0.25 mm stainless steel wire mesh to prevent escape of mosquitoes and ingress of other insects. The cages are covered by an aluminum security mesh to prevent penetration of the cages by branches and other missiles in the advent of a tropical cyclone. Parts of the cage are protected from UV light and rainfall by 90% shade cloth and a vinyl cover. A wooden structure simulating the understory of a Queenslander-style house is also situated at one end of each cage. The remainder of the internal aspect of the cage is covered with mulch and potted plants to emulate a typical yard. An air conditioning system comprised of two external ACs that feed cooled, moistened air into the cage units. The air is released from the central ceiling beam from a long cloth tube that disperses the airflow and also prevents mosquitoes from escaping the cage via the AC system. Sensors located inside and outside the cage monitor ambient temperature and relative humidity, with AC controlled to match ambient conditions. Data loggers set in the cages and outside found a <2 °C temperature difference. Additional security features include air curtains over exit doors, sticky traps to monitor for escaping mosquitoes between layers of the mesh, a lockable vestibule leading from the connecting corridor to the cage and from inside to outside of the insectary, and screened (0.25 mm mesh) drains within the insectary and the cage. A set of standard operating procedures (SOP) has been developed to ensure that security is maintained and for enhanced surveillance for escaping mosquitoes on the JCU campus where the MRF is located. A cohort of male and female Aedes aegypti mosquitoes were released in the cage and sampled every 3-4 days to determine daily survival within the cage; log linear regression from BG-sentinel trapping collections produced an estimated daily survival of 0.93 and 0.78 for females and males, respectively.Conclusions/significanceThe MRF SFS allows us to test novel control strategies within a secure, contained environment. The air-conditioning system maintains conditions within the MRF cages comparable to outside ambient conditions. This cage provides a realistic transitional platform between the laboratory and the field in which to test novel control measures on quarantine level insects.
| S-EPMC3062535 | biostudies-literature
Project description:Aedes aegypti mosquitoes, main vectors for numerous flaviviruses, have olfactory preferences and are capable of olfactory learning especially when seeking their required environmental conditions to lay their eggs. In this study, we showed that semiochemical conditions during Aedes aegypti larval rearing affected future female choice for oviposition: water-reared mosquitoes preferred to lay eggs in water or p-cresol containers, while skatole reared mosquitoes preferred skatole sites. Using two independent behavioural assays, we showed that this skatole preference was lost in mosquitoes infected with dengue virus. Viral RNA was extracted from infected female mosquito heads, and an increase of virus load was detected from 3 to 10 days post infection, indicating replication in the insect head and possibly in the central nervous system. Expression of selected genes, potentially implied in olfactory learning processes, were also altered during dengue infection. Based on these results, we hypothesise that dengue virus infection alters gene expression in the mosquito's head and is associated with a loss of olfactory preferences, possibly modifying oviposition site choice of female mosquitoes.
| S-EPMC6123472 | biostudies-literature
Project description:BackgroundCurrent Aedes aegypti larval control methods are often insufficient for preventing dengue epidemics. To improve control efficiency and cost-effectiveness, some advocate eliminating or treating only highly productive containers. The population-level outcome of this strategy, however, will depend on details of Ae. aegypti oviposition behavior.Methodology/principal findingsWe simultaneously monitored female oviposition and juvenile development in 80 experimental containers located across 20 houses in Iquitos, Peru, to test the hypothesis that Ae. aegypti oviposit preferentially in sites with the greatest potential for maximizing offspring fitness. Females consistently laid more eggs in large vs. small containers (??=?9.18, p<0.001), and in unmanaged vs. manually filled containers (??=?5.33, p<0.001). Using microsatellites to track the development of immature Ae. aegypti, we found a negative correlation between oviposition preference and pupation probability (??=?-3.37, p<0.001). Body size of emerging adults was also negatively associated with the preferred oviposition site characteristics of large size (females: ??=?-0.19, p<0.001; males: ??=?-0.11, p?=?0.002) and non-management (females: ??=?-0.17, p<0.001; males: ??=?-0.11, p<0.001). Inside a semi-field enclosure, we simulated a container elimination campaign targeting the most productive oviposition sites. Compared to the two post-intervention trials, egg batches were more clumped during the first pre-intervention trial (??=?-0.17, P<0.001), but not the second (??=?0.01, p?=?0.900). Overall, when preferred containers were unavailable, the probability that any given container received eggs increased (??=?1.36, p<0.001).Conclusions/significanceAe. aegypti oviposition site choice can contribute to population regulation by limiting the production and size of adults. Targeted larval control strategies may unintentionally lead to dispersion of eggs among suitable, but previously unoccupied or under-utilized containers. We recommend integrating targeted larval control measures with other strategies that leverage selective oviposition behavior, such as luring ovipositing females to gravid traps or egg sinks.
| S-EPMC3341338 | biostudies-literature
Project description:BackgroundMicrobial larvicides containing both LysiniBacillus sphaericus and Bacillus thuringiensis svar. israelensis (Bti) insecticidal crystals can display advantages for mosquito control. This includes a broader action against larvae that are refractory to the Binary (Bin) toxin from L. sphaericus, as Bin-resistant Culex quinquefasciatus and Aedes aegypti naturally refractory larvae, which often co-habit urban areas of endemic countries for arboviruses. Our principal goal was to assess the toxicity of a combined L. sphaericus/Bti larvicide (Vectomax FG™) to Cx. quinquefasciatus (susceptible CqS and Bin-resistant CqR) and Ae. aegypti (Rocke) and to determine its persistence in the breeding sites with those larvae.MethodsThe toxicity of a combined L. sphaericus/Bti product (VectoMax FG™) to larvae was performed using bioassays, and persistence was evaluated in simulate field trials carried out under the shade, testing two label concentrations during 12 weeks. A laboratory strain SREC, established with CqS and CqR larvae, was kept during four generations to evaluate the ability of the L. sphaericus/Bti to eliminate resistant larvae.ResultsThe L. sphaericus/Bti showed toxicity (mg/L) to larvae from all strains with a decreasing pattern for CqS (LC50 = 0.006, LC90 = 0.030), CqR (LC50 = 0.009, LC90 = 0.069), and Rocke (LC50 = 0.042, LC90 = 0.086). In a simulated field trial, the larvicide showed a persistence of 6 weeks and 8 weeks, controlling larvae from all strains in containers with 100 L of water, using 2 g or 4 g per container (100 L), respectively. The treatment of SREC larvae with L. sphaericus/Bti showed its capacity to eliminate the Bin-resistant individuals using suitable concentrations to target those larvae.ConclusionsOur results showed the high efficacy and persistence of the L. sphaericus/Bti larvicide to control Cx. quinquefasciatus and Ae. aegypti that might cohabit breeding sites. These findings demonstrated that such larvicides can be an effective tool for controlling those species in urban areas with a low potential for selecting resistance.
| S-EPMC11401406 | biostudies-literature
Project description:The mosquito Aedes aegypti is the main vector of arboviroses and current approaches to control this vector are not sufficiently effective. Adult traps, such as the BG-Sentinel (BGS), have been successfully used for mosquito surveillance and can also suppress vector populations. A new "passive" trap for gravid Ae. aegypti (Gravid Aedes Trap-GAT) has been shown efficient for Aedes collection and suppress Ae. albopictus populations using mass trapping techniques. Here the GAT was evaluated for the first time as a new tool to control Ae. aegypti in semi-field conditions using simulated outdoor environments (SOE). Two identical large screened chambers inside of a SOE containing different numbers and sizes of artificial breeding sites were used to assess the trapping efficiency of the GAT. One hundred mosquitoes were released into the chambers, and recapture rates evaluated after 48h. The parity status of the captured mosquitoes was also recorded. The number of eggs laid, and breeding productivity were also monitored when using different numbers and sizes of breeding sites. The BGS trap was used here as a control (gold standard) trap to compare capture rates to those of the GAT. The GAT recaptured between 50-65% of the mosquitoes independent of the number and sizes of the breeding sites in the SOEs, whereas the BGS recaptured 60-82% of the females. Both traps showed similar results regarding to the parity status of recaptured mosquitoes. Our results confirmed the effectiveness of GAT for the capture of adult female Ae. aegypti in simulated field environments. The BGS trap recaptured gravid Ae. aegypti before egg-laying in different sizes and number of breading sites, whereas the oviposition activity occurred prior to recapture mosquitoes in the GAT. Based on the results, we believe that GAT is a promising candidate for mass-trapping intervention in urban settings, but a source reduction intervention should be made prior trap deployment. Therefore, we suggest future field studies to confirm the use of GAT as a complementary tool in vector control activities.
| S-EPMC8084243 | biostudies-literature
Project description:Arbovirus diseases, such as dengue, chikungunya, and Zika, are important public health problems. Controlling the major vector, Aedes aegypti, is the only approach to suppressing these diseases. The surveillance of this mosquito species needs effective collecting methods. In this study, a simple MosHouse sticky trap was evaluated in a semi-field condition. Our results demonstrated the efficiency of this trap in collecting Ae. aegypti males, and no significant difference (p > 0.05) in the numbers of males was detected when compared with the widely used BG- Sentinel trap. However, there were significantly lower numbers of females (p < 0.05) collected using the MosHouse trap when compared to the BG-Sentinel trap. We also found a significant difference (p < 0.05) in the collected numbers between irradiated and non-irradiated males. More irradiated males were collected in the MosHouse traps. The improvement of male collection was achieved with the addition of a sugar stick and sticky flags. Significantly higher numbers of males were collected in the MosHouse trap with sticky flags compared to the original one when they were released independently of females, but both were collected in higher numbers when they were released together (p < 0.05). In conclusion, our experiments demonstrated that the MosHouse trap could sample Ae. aegypti, especially males, as efficiently as the established BG-Sentinel trap, while the cost was more than 50 times lower, showing the potential of the MosHouse trap for improved Ae. aegypti male and female surveillance with very large numbers of traps at affordable costs. In addition, significantly (p < 0.001) increased male sampling was achieved by adding an external sticky flag on the MosHouse trap, providing an avenue for further development of the novel male-trapping strategy.
| S-EPMC9693147 | biostudies-literature
Project description:With Wolbachia-based arbovirus control programs being scaled and operationalised around the world, cost effective and reliable detection of Wolbachia in field samples and laboratory stocks is essential for quality control. Here we validate a modified loop-mediated isothermal amplification (LAMP) assay for routine scoring of Wolbachia in mosquitoes from laboratory cultures and the field, applicable to any setting. We show that this assay is a rapid and robust method for highly sensitive and specific detection of wAlbB Wolbachia infection within Aedes aegypti under a variety of conditions. We test the quantitative nature of the assay by evaluating pooled mixtures of Wolbachia-infected and uninfected mosquitoes and show that it is capable of estimating infection frequencies, potentially circumventing the need to perform large-scale individual analysis for wAlbB infection status in the course of field monitoring. These results indicate that LAMP assays are useful for routine screening particularly under field conditions away from laboratory facilities.
| S-EPMC6867633 | biostudies-literature
Project description:BackgroundEntomopathogenic fungi are potential candidates for use in integrated vector management, with recent emphasis aimed at developing adult mosquito control methods. Here we investigated the persistence of the fungus Metarhizium anisopliae when tested against female A. aegypti under field conditions.MethodsBlack cotton cloths impregnated with M. anisopliae conidia, formulated in vegetable oil + isoparaffin, were maintained on a covered veranda for up to 30 days. At specific times, pieces of the cloths were removed, placed in Tween 80 and the resuspended conidia were sprayed directly onto mosquitoes. The persistence of conidia impregnated on black cloths using three different carriers was evaluated in test rooms. Fifty mosquitoes were released into each room and after a 5 day period, the surviving insects were captured. Another 50 insects were then released into each room. The capacity of the fungus at reducing mosquito survival was evaluated over a total of 35 days.ResultsConidia extracted from cloths maintained on the veranda for 2 to 18 days remained virulent, with 28 to 60% mosquito survival observed. Mosquito survival following exposure to fungus impregnated cloths showed that fungus + Tween caused similar reductions to that of fungus + vegetable oil. Mosquitoes exposed to the formulation fungus + vegetable oil had survival rates of 36% over the first 5 days of the experiment. Following the release of the second cohort of mosquitoes (6-11days), survival increased to 50%. The survival of the 12-17 day cohort (78%) was statistically equal to that of the controls (84%). Formulation of the fungus in vegetable oil + isoparaffin increased the persistence of the fungus, with the 18-23 day cohort (64% survival) still showing statistical differences to that of the controls (87% survival).ConclusionsThe potential of entomopathogenic fungi for the control of adult A. aegypti was confirmed under field conditions. Vegetable oil + isoparaffin formulations of M. anisopliae significantly increased the effectiveness of the fungus, thus reducing the need for frequent changes of black cloths in residences. Our future aim is to obtain effective control of mosquito populations, with cloths only needing to being replaced once a month.
| S-EPMC4021620 | biostudies-literature