Regulation of Aedes aegypti Population Dynamics in Field Systems: Quantifying Direct and Delayed Density Dependence

Walsh, Rachael K.; Aguilar, Cristobal L.; Facchinelli, Luca; Valerio, Laura; Ramsey, Janine M.; Scott, Thomas W.; Lloyd, Alun L.; Gould, Fred

doi:10.4269/ajtmh.12-0378

Cited by 36 publications

(59 citation statements)

References 37 publications

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“…However, several studies have expressed concern that a density-dependent increase in mosquito fitness may impede population suppression strategies [15, 18]. Our model predicts that increasing density-independent mortality reduces adult numbers despite alleviating the effects of competition on mosquito fitness, and therefore suggests that interventions to suppress populations by killing juveniles and adults are likely to be helpful.…”

Section: Discussionmentioning

confidence: 75%

“…However, in A. aegypti , experimental studies have shown that fecundity, and juvenile survival and development rates, vary strongly depending on the level of larval density-dependent competition for food [14–17]. Larval density-dependent demographic variation in field populations has proven difficult to quantify because mosquito populations have overlapping generations [15, 16, 18]. However, field observations of A. aegypti suggest that competition is often relatively intense.…”

Section: Introductionmentioning

confidence: 99%

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Predicting Wolbachia invasion dynamics in Aedes aegypti populations using models of density-dependent demographic traits

et al. 2016

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BackgroundArbovirus transmission by the mosquito Aedes aegypti can be reduced by the introduction and establishment of the endosymbiotic bacteria Wolbachia in wild populations of the vector. Wolbachia spreads by increasing the fitness of its hosts relative to uninfected mosquitoes. However, mosquito fitness is also strongly affected by population size through density-dependent competition for limited food resources. We do not understand how this natural variation in fitness affects symbiont spread, which limits our ability to design successful control strategies.ResultsWe develop a mathematical model to predict A. aegypti–Wolbachia dynamics that incorporates larval density-dependent variation in important fitness components of infected and uninfected mosquitoes. Our model explains detailed features of the mosquito–Wolbachia dynamics observed in two independent experimental A. aegypti populations, allowing the combined effects on dynamics of multiple density-dependent fitness components to be characterized. We apply our model to investigate Wolbachia field release dynamics, and show how invasion outcomes can depend strongly on the severity of density-dependent competition at the release site. Specifically, the ratio of released relative to wild mosquitoes required to attain a target infection frequency (at the end of a release program) can vary by nearly an order of magnitude. The time taken for Wolbachia to become established following releases can differ by over 2 years. These effects depend on the relative fitness of field and insectary-reared mosquitoes.ConclusionsModels of Wolbachia invasion incorporating density-dependent demographic variation in the host population explain observed dynamics in experimental A. aegypti populations. These models predict strong effects of density-dependence on Wolbachia dynamics in field populations, and can assist in the effective use of Wolbachia to control the transmission of arboviruses such as dengue, chikungunya and zika.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-016-0319-5) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Predicting Wolbachia invasion dynamics in Aedes aegypti populations using models of density-dependent demographic traits

et al. 2016

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“…; Walsh et al . ). A. aegypti rely on human blood to reproduce, and their larval habitat consists of water containers close to human dwellings, such as water storage jars and pot plant plates (Southwood et al .…”

Section: Introductionmentioning

confidence: 97%

Density‐dependent population dynamics in Aedes aegypti slow the spread of wMel Wolbachia

Hancock

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Callahan

et al. 2016

Journal of Applied Ecology

125

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Summary1. Field release of endosymbiotic Wolbachia bacteria into wild Aedes aegypti mosquito populations is a promising strategy for biocontrol of dengue. This strategy requires successful Wolbachia invasion through the mosquito vector population. Natural variation in mosquito fitness due to density-dependent competition for limited food resources may influence Wolbachia invasion. We know little about these effects, largely because our understanding of density-dependent dynamics in mosquito populations is limited. 2. We developed an empirical model of A. aegypti-Wolbachia dynamics where food resources available to the developing larvae are limited. We assessed the extent of density-dependent regulation in our A. aegypti population using a Bayesian statistical model that estimates the temporal variation in mosquito fitness components. We monitored the spread of Wolbachia and assessed the effect of the bacteria on larval fitness components. 3. We demonstrate that mosquito population growth is regulated by strong larval densitydependent variation in mosquito fitness components. Wolbachia spread was slowed by this heterogeneity in mosquito fitness, which reduces the capacity of the bacteria to invade. However, we found no evidence that Wolbachia affects larval fitness components. 4. Synthesis and applications. We demonstrate that the extent and form of density-dependent dynamics in the host population can have a major influence on Wolbachia invasion. These findings help explain slow Wolbachia invasion rates and indicate that the success of field release strategies for dengue control can depend on attaining high Wolbachia frequencies in the mosquito population.

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“…Given the public health significance of these mosquitoes and the potentially large impact that density dependence could have on the success of mosquito control measures, surprisingly little is known about density dependence in these species under natural conditions. Although laboratory studies have provided insight into temperature and resource dependent growth and development of immature mosquitoes (Gilpin and McCleland 1979, Rueda et al 1990, Arrivillaga et al 2004), translating these into descriptions of natural environments is challenging (Walsh et al 2013). For instance, it is unclear how levels of nutrients used in lab experiments compare to those present in reality, or how development of immatures differs between constant and variable temperature settings.…”

Section: Introductionmentioning

confidence: 99%

“…the nature of food being consumed and the feeding habits of larvae) and in terms of its outcome (e.g. a description of how larval survival and/or development depends on the number of larvae present) (Walsh et al 2013). Dynamics of immature stages of Ae.…”

Section: Introductionmentioning

confidence: 99%

Comparison of two detailed models of Aedes aegypti population dynamics

et al. 2016

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The success of control programs for mosquito borne diseases can be enhanced by crucial information provided by models of the mosquito populations. Models, however, can differ in their structure, complexity and biological assumptions, and these differences impact their predictions. Unfortunately, it is typically difficult to determine why two complex models make different predictions because we lack structured side-by-side comparisons of models using comparable parameterization. Here we present a detailed comparison of two complex, spatially-explicit, stochastic models of the population dynamics of Aedes aegypti, the main vector of dengue, yellow fever, chikungunya and Zika viruses. Both models describe the mosquito's biological and ecological characteristics, but differ in complexity and specific assumptions. We compare the predictions of these models in two selected climatic settings, a tropical and weakly seasonal climate in Iquitos, Peru, and a temperate and strongly seasonal climate in Buenos Aires, Argentina. Both models were calibrated to operate at identical average densities in unperturbed conditions in both settings, by adjusting parameters regulating densities in each model (number of larval development sites and amount of nutritional resources). We show that the models differ in their sensitivity to environmental conditions (temperature and rainfall), and trace differences to specific model assumptions. Temporal dynamics of the Ae. aegypti populations predicted by the two models differ more markedly under strongly seasonal Buenos Aires conditions. We use both models to simulate killing of larvae and/or adults with insecticides in selected areas. We show that predictions of population recovery by the models differ substantially, an effect likely related to model assumptions regarding larval development and (direct or delayed) density dependence. Our methodical comparison provides important guidance for model improvement by identifying key areas of Ae. aegypti ecology that substantially affect model predictions, and revealing the impact of model assumptions on population dynamics predictions in unperturbed and perturbed conditions.

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Regulation of Aedes aegypti Population Dynamics in Field Systems: Quantifying Direct and Delayed Density Dependence

Cited by 36 publications

References 37 publications

Predicting Wolbachia invasion dynamics in Aedes aegypti populations using models of density-dependent demographic traits

Predicting Wolbachia invasion dynamics in Aedes aegypti populations using models of density-dependent demographic traits

Density‐dependent population dynamics in Aedes aegypti slow the spread of wMel Wolbachia

Comparison of two detailed models of Aedes aegypti population dynamics

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