Modelling the<i>Wolbachia</i>Incompatible Insect Technique: strategies for effective mosquito population elimination

Pagendam, Dan; Trewin, Brendan J; Johnson, Brian J.; Snoad, Nigel; Ritchie, Stuart J.; Hoffmann, Ary A.; Staunton, Kyran M.; Paton, Christopher J.; Beebe, Nigel W.

doi:10.1101/2020.07.13.201483

Cited by 5 publications

(8 citation statements)

References 35 publications

(49 reference statements)

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“…No w AlbB-positive larvae were detected in the subsequent six weeks of ovitrap deployment, and no w AlbB-positive female adults were detected in the subsequent 38 weeks, suggesting that w AlbB mosquitoes failed to establish in the field as the wildtype population bounced back. This agrees with a previous study that showed that a rather high threshold of ∼20% w AlbB in the field population was needed to effect w AlbB invasion and establishment ( 8, 32, 33 ).…”

Section: Main Textsupporting

confidence: 93%

Wolbachia-mediated sterility suppressesAedes aegyptipopulations in the urban tropics

Ching¹

2021

Preprint

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Incompatible insect technique (IIT) via releases of male Wolbachia-infected mosquitoes is a promising tool for dengue control. In a three-year trial in Singaporean high-rise housing estates, we demonstrated that Wolbachia-based IIT dramatically reduces both wildtype Aedes aegypti populations [reductions of 92.7% (95% CI: 84.7%-95.8%) and 98.3% (97.7%-99.8%)] and dengue incidence [reductions of 71% (43%-87%) to 88% (57%-99%)] in the targeted areas. The study highlights the need to ensure adequate vertical distribution of released males in high-rise buildings, address immigration of wildtype females from neighboring areas, and prevent and mitigate stable establishment of Wolbachia in field mosquito populations. Our results demonstrate the potential of Wolbachia-based IIT (supplemented with irradiation, in Singapore's context) for strengthening dengue control in tropical cities, where dengue burden is the greatest.

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Section: Main Textsupporting

confidence: 93%

Wolbachia-mediated sterility suppressesAedes aegyptipopulations in the urban tropics

Ching¹

2021

Preprint

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“…Our simulations of the releases conducted twice a week over 12 weeks predict that increasing the overflowing ratio from 14:1 up to 40:1 achieves suppression levels 61-93%, but larger releases (≥20:1) dramatically increase the chance of Wolbachia establishment if the sex sorting error is greater than 10 -7 (Figure S1). This is consistent with a recent modeling study of the IIT campaign in Innisfail (44) which found that a sex sorting error rate of 10 -7 or less is needed to achieve a low probability of Wolbachia establishment, along with 'adaptive releases' three times a week that start with an overflooding ratio of 5:1 or 15:1, and decrease in sze as the population is suppressed over time (44).…”

Section: Discussionsupporting

confidence: 90%

Eliminating Aedes aegypti from its southern margin in Australia: insights from genomic data and simulation modeling

Rašić

Filipović

et al. 2021

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A rare example of a successful long-term elimination of the mosquito Aedes aegypti is in Brisbane, Queensland, where the legislatively-enforced removal of rainwater tanks drove its disappearance by the mid-1950s. However, a decade-long drought led to the mass installation of rainwater tanks throughout the region, re-introducing critical breeding sites for the mosquito’s persistence in this subtropical region. With Ae. aegypti re-invading towns just 150 km north of Brisbane, we examined the potential for their sustained elimination. Through genomic analyses, we estimated historical expansion and current isolation between neighboring populations as close as 15 kilometers. The estimated recent migration rate, entomological and meteorological data were used to calibrate the simulations of elimination campaigns in the two southernmost populations. Our simulations indicate that Ae. aegypti could be eliminated with moderate release numbers of incompatible Wolbachia-infected (IIT) males (sorted with an error rate ≤10-6) if non-compliant rainwater tanks are removed first. With this combined campaign, highly effective suppression (>99%) was predicted in both towns, and complete elimination was predicted in 35% of simulations in one town. Without tank removal, however, IIT led to a moderate suppression (61-93%) even with a 40:1 ratio of released IIT males to local males. Moreover, with a ratio of >20:1, Wolbachia establishment was predicted when the sorting error was >10-7. Our conservative estimates of intervention outcomes inform the planning of Ae. aegypti elimination in the region, and offer insight into the effective combinations of conventional and novel control tools, particularly for vulnerable mosquito populations at range margins.SignificanceAfter decades of range stagnation in Australia, the Aedes aegypti mosquito is expanding southward, approaching the most-densely-populated areas of Queensland. Using population genomics and simulation modeling of elimination campaigns, we show that Australia’s southernmost populations of this disease vector are genetically isolated and could be eliminated with moderate releases of incompatible Wolbachia-infected males if major larval breeding sites (non-compliant rainwater tanks) are removed first. The risk of Wolbachia establishment for this approach is low, and so is the risk of quick mosquito re-invasion. Our conservative estimates of intervention outcomes inform the planning of Ae. aegypti elimination in the region, and offer new insight into the benefits of combining conventional and novel control tools, particularly for mosquito populations at range margins.

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“…The presented results reinforce the idea that performing radiation as a strategy to achieve male sterilization would enable the utilization of perfect sexing methods necessary to avoid the release of [20,67,68], the most relevant concern related to the Wolbachia-based suppression strategies is eliminated. In fact, the establishment in nature of mosquito lines with altered Wolbachia infection, which may compromise the long-term efficiency of IIT strategy, will be prevented by combining superior sexing procedures with opportune release programmes [69] in the case of both Uni-CI and Bi-CI patterns. In the latter case, the above-mentioned measures will be particularly effective because Bi-CI lowers the chance for the establishment of released mosquitoes in the field [15,18,49].…”

Section: Resultsmentioning

confidence: 99%

Increased biting rate and decreasedWolbachiadensity in irradiatedAedesmosquitoes

Moretti

López-Knowles

Fabbri

et al. 2021

Preprint

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Releasing considerable numbers of radiation-sterilized males is a promising strategy to suppress mosquito vectors. However, under large-scale settings, small percentages of biting females can also be released in the field. Currently, the effects of the irradiation on host-seeking and host-biting behaviors have not been exhaustively investigated. Information is also lacking regarding the effects of a sterilizing treatment on the endosymbiotic bacterium Wolbachia , that is known to attenuate the vector competence of infected mosquito species. To ascertain the risks associated with the release of irradiated females, the pupae of two Aedes albopictus strains, differing by their natural or artificial Wolbachia infection type, were X-ray-treated using various doses to monitor key fitness parameters and biting behavior over two weeks. The effect of the radiation on Wolbachia was investigated by qPCR and FISH analysis. Radiation doses of 35 and 45 Gy completely inhibited progeny production but did not significantly affect Ae. albopictus female survival and flight ability, and caused a tripling of the number of bites per female per week compared to untreated controls. These results were also confirmed in Ae. aegypti after treatment at 5 0 Gy. A partial Ae. albopictus female sterility was achieved at 28 Gy but the number of weekly bites more than doubled compared to the controls. The Wolbachia density showed a significant downward trend in 45-Gy-irradiated females and decreased with adult aging and in younger treated pupae. This trend was confirmed in ovaries but not in extraovaric tissues. FISH analysis evidenced a strongly reduced Wolbachia -specific fluorescence in the ovaries of 13±1-day-old females. These findings suggested that irradiation could markedly increase the vectorial capacity of female mosquitoes, raising concerns about open field programs involving the release of substantial numbers of irradiated mosquitoes in the absence of perfect sexing methods.

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Modelling theWolbachiaIncompatible Insect Technique: strategies for effective mosquito population elimination

Cited by 5 publications

References 35 publications

Wolbachia-mediated sterility suppressesAedes aegyptipopulations in the urban tropics

Wolbachia-mediated sterility suppressesAedes aegyptipopulations in the urban tropics

Eliminating Aedes aegypti from its southern margin in Australia: insights from genomic data and simulation modeling

Increased biting rate and decreasedWolbachiadensity in irradiatedAedesmosquitoes

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