Field evaluation of seasonal trends in relative population sizes and dispersal pattern of Aedes albopictus males in support of the design of a sterile male release strategy

Lakan

2020

Preprint

Background: Although great strides have been made in controlling malaria, the disease is of significant public health importance. Historically, efforts to control the vector has concentrated on adult vector control targeting the female Anopheles mosquitoes. As there is now a focus on eliminating residual malaria from KwaZulu-Natal, new strategies are being investigated to increase the impact of malaria elimination strategies. Greater attention is now being given to larval control, as a complementary measure to indoor residual spraying. However, there is a large gap in knowledge of the bionomics of the larval stages of this mosquito vector of malaria in South Africa. In order to focus on both larval and adult mosquito control methods, larval development and the reproductive stages of the vector were investigated since these variables influences our ability to impact mosquito populations through larval control. This study was therefore conducted to determine the peak eruption times and the emergent sex ratios, as well as the peak egg oviposition time in order to attack the mosquito when it is at its most vulnerable and when control interventions will have the most impact.Results: Oviposition studies showed two peaks corresponding with late evening and again just before dawn. Most eggs were also laid in the first half of the night (18h00 – midnight). Most mosquitoes erupted just after sunset and the sex ratios showed that twice as many females as males emerged. Females readily took a bloodmeal after oviposition or just after erupting. Hatch rate to viable first instar larvae was 74.5%.Conclusions: The results of this study have provided information as to when interventions would be most effective in controlling mosquito populations and have provided information that highlights the value of larval control as a complementary measure to adult mosquito control. The most vulnerable stages of the female Anopheles arabiensis are when they have just emerged or when they have just oviposited. Vector control strategies should be designed to target these vulnerable stages at the breeding sites in order to have maximum impact.

Section: Discussionsupporting

confidence: 83%

Bionomics of Anopheles Arabiensis from Mamfene in KwaZulu-Natal (South Africa): An Area of High Malaria Transmission in the Province

Lakan

2020

Preprint

“…The study also supports the recommendation from investigations into the use of the sterile insect technique (SIT) that more sterile males be introduced into an area to outcompete non-sterile males [32]. This study has demonstrated that even under optimum conditions fewer males than females are produced and hence the release of a large number of sterile males would dilute the competition from the smaller number of males produced in the wild [33]. Furthermore, male control can be achieved by baits and swarm space spraying [34] However, according to Maharaj [26], there is a slight variation in sex ratio across seasons requiring that SIT programmes constantly monitor the wild male population to adjust the release rate over time.…”

Section: Discussionsupporting

confidence: 80%

Bionomics of Anopheles arabiensis from Mamfene in KwaZulu-Natal (South Africa): an area of high malaria transmission in the province

Lakan

2020

Preprint

Background Although great strides have been made in controlling malaria, the disease is of significant public health importance. Historically, efforts to control the vector has concentrated on adult vector control targeting the female Anopheles mosquitoes. As there is now a focus on eliminating residual malaria from KwaZulu-Natal, new strategies are being investigated to increase the impact of malaria elimination strategies. Greater attention is now being given to larval control, as a complementary measure to indoor residual spraying. However, there is a large gap in knowledge of the bionomics of the larval stages of this mosquito vector of malaria in South Africa. In order to focus on both larval and adult mosquito control methods, larval development and the reproductive stages of the vector were investigated since these variables influences our ability to impact mosquito populations through larval control. This study was therefore conducted to determine the peak eruption times and the emergent sex ratios, as well as the peak egg oviposition time in order to attack the mosquito when it is at its most vulnerable and when control interventions will have the most impact. Results Oviposition studies showed two peaks corresponding with late evening and again just before dawn. Most eggs were also laid in the first half of the night (18h00 – midnight). Most mosquitoes erupted just after sunset and the sex ratios showed that twice as many females as males emerged. Females readily took a bloodmeal after oviposition or just after erupting. Hatch rate to viable first instar larvae was 74.5%. Conclusions The results of this study have provided information as to when interventions would be most effective in controlling mosquito populations and have provided information that highlights the value of larval control as a complementary measure to adult mosquito control. The most vulnerable stages of the female Anopheles arabiensis are when they have just emerged or when they have just oviposited. Vector control strategies should be designed to target these vulnerable stages at the breeding sites in order to have maximum impact.

“…This later estimate is similar to the carrying capacity of our study ( F = 3283.9)—thus our ecological assumptions are coherent with known hot-spots in Italy. On Reunion Island, densities of over 5800 males/ha have been reported using mark-release-recapture with mice-baited BG-Sentinel traps 74 —our modelling predicts that, if using SIT alone, it would be very difficult to bring R 0 below one with such high mosquito densities.…”

Section: Discussionmentioning

confidence: 75%

Biopesticides improve efficiency of the sterile insect technique for controlling mosquito-driven dengue epidemics

Pleydell

Bouyer

2019

Commun Biol

Various mosquito control methods use factory raised males to suppress vector densities. But the efficiency of these methods is currently insufficient to prevent epidemics of arbovirus diseases such as dengue, chikungunya or Zika. Suggestions that the sterile insect technique (SIT) could be “boosted” by applying biopesticides to sterile males remain unquantified. Here, we assess mathematically the gains to SIT for Aedes control of either: boosting with the pupicide pyriproxifen (BSIT); or, contaminating mosquitoes at auto-dissemination stations. Thresholds in sterile male release rate and competitiveness are identified, above which mosquitoes are eliminated asymptotically. Boosting reduces these thresholds and aids population destabilisation, even at sub-threshold release rates. No equivalent bifurcation exists in the auto-dissemination sub-model. Analysis suggests that BSIT can reduce by over 95% the total release required to circumvent dengue epidemics compared to SIT. We conclude, BSIT provides a powerful new tool for the integrated management of mosquito borne diseases.