Evaluation of a fitness-disrupting chemical for the control of Aedes albopictus mosquitoes Öffentlichkeit
Perez, Alexandra (Spring 2021)
Abstract
Though Aedes albopictus mosquitoes have historically been considered secondary vectors of arboviruses such as dengue and chikungunya, the species has recently undergone a dramatic global expansion due to its ecological plasticity and strong competitive aptitude. Likewise, the pathogens vectored by Ae. albopictus have a high potential for geographic spread into areas where these vectors invade. Without vaccines or medical treatments for most arboviruses transmitted by Aedes mosquitoes, vector control is our most useful tool in disease prevention. Insect growth regulators such as pyriproxyfen (PPF) have been used to control mosquitoes at varying life stages due to its inhibition of morphogenesis, reproduction, and embryogenesis. Although PPF is effective and versatile in laboratory experiments, its use in mosquito control programs is limited by the high-cost, labor-intensive methods that are required to have a tangible, population-level impact. This study aimed to evaluate the use of PPF ingestion by female Ae. albopictus on inhibiting mosquito growth and reproduction at varying life stages. A dietary formulation of PPF combined with sugar solution was created, and sugar feeders were designed to allow mosquitoes to feed while reducing tarsal exposure to PPF. After access to PPF/sugar feeders containing 0, 1, 5, or 10 mg/mL PPF for 24 hours, female Ae. albopictus were reared in-laboratory and individualized for oviposition. Survival, fecundity, and fertility were determined for each female, and any transgenerational effects of parental ingestion of PPF were observed in the pupation and adult emergence rates of offspring. A combination of these experimental results and published literature were used to inform two stage-based matrix projections to determine the population-level effects of dietary PPF on Ae. albopictus. Overall, adult survival and fertility were not impacted by any of the tested PPF doses. Fecundity, pupation, and adult emergence were significantly reduced following ingestion of 5 mg/mL PPF (24%, 47%, and 43% reductions, respectively). Fecundity was reduced by 23% following treatment with 1 mg/mL PPF, and pupation was reduced by 22% following treatment with 10 mg/mL PPF. Treatment with 5 mg/mL PPF was selected for calculation of the matrix model parameters as this dose had the most consistent effect on reproductive output and outcome across all mosquito life stages. Population projections with no intervention grew exponentially over 100 days (λ = 1.05) while populations receiving treatment were projected to decay within that same time frame (λ = 0.94). The use of PPF/sugar feeding stations, in combination with current regimes, could provide a mosquito control strategy that acts through chemical and biological pathways to target mosquitoes at different life stages in a design that can be implemented easily at the household level.
Table of Contents
Abstract iv
Acknowledgements vi
List of Tables ix
List of Figures x
Glossary of Terms xi
Introduction 1
Biology and Behavior of Ae. albopictus 2
Impact of Ae. albopictus on Health
Control Strategies for Ae. albopictus 6
Insect Growth Regulators (IGRs) 9
Use of Pyriproxyfen (PPF) for Mosquito Control 10
Dietary Formulations of PPF 14
Hypotheses 16
Research Objectives 16
Methodology 18
Mosquito Rearing 18
Test Chemical 19
Susceptibility of Pupae to PPF 19
Preparation of PPF Sugar Feeding Stations 19
Assessing Adult Female Survival 22
Evaluation of Female Reproductive Output 22
Evaluation of Transgenerational Effects of Dietary PPF 24
Statistical Analyses of Experimental Data 24
Mathematical Model Development 25
Model Assumptions and Initial Conditions 28
Model Statistics 29
Results 31
Pupal Susceptibility to PPF 31
Adult Female Survival 31
Sterilizing Effects of Dietary PPF 32
Transgenerational Effects of Dietary PPF 32
Population Projections 33
Discussion 35
Conclusions 42
References 44
Tables 51
Figures 55
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