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This study presents a systematic review and pooled This study presents a systematic review and pooled survival analysis quantifying the effects of desiccation stress (humidity) and temperature on the adult female longevity of Aedes aegypti and Aedes albopictus, the primary mosquito vectors of arboviral diseases such as dengue, Zika, chikungunya, and yellow fever. The research addresses a critical gap in vector ecology and epidemiology by providing a comprehensive, quantitative model of how humidity influences adult mosquito survival, alongside temperature effects, to improve understanding of transmission dynamics and enhance predictive models of disease risk.
Background
Aedes aegypti and Ae. albopictus are globally invasive mosquito species that transmit several major arboviruses.
Adult female mosquito longevity strongly impacts transmission dynamics because mosquitoes must survive the extrinsic incubation period (EIP) to become infectious.
While temperature effects on mosquito survival have been widely studied and incorporated into models, the role of humidity remains poorly quantified despite being ecologically significant.
Humidity influences mosquito survival via desiccation stress, affecting water loss and physiological function.
Environmental moisture also indirectly affects mosquito populations by altering evaporation rates in larval habitats, impacting larval development and adult body size, which affects vectorial capacity.
Understanding the temperature-dependent and non-linear effects of humidity can improve ecological and epidemiological models, especially in arid, semi-arid, and seasonally dry regions, which are understudied.
Objectives
Systematically review experimental studies on temperature, humidity, and adult female survival in Ae. aegypti and Ae. albopictus.
Quantify the relationship between humidity and adult survival while accounting for temperature’s modifying effect.
Provide improved parameterization for models of mosquito populations and arboviral transmission.
Methods
Systematic Literature Search: 1517 unique articles screened; 17 studies (16 laboratory, 1 semi-field) met inclusion criteria, comprising 192 survival experiments with ~15,547 adult females (8749 Ae. aegypti, 6798 Ae. albopictus).
Inclusion Criteria: Studies must report survival data for adult females under at least two temperature-humidity regimens, with sufficient methodological detail on nutrition and hydration.
Data Extraction: Variables included species, survival times, mean temperature, relative humidity (RH), and provisioning of water, sugar, and blood meals. Saturation vapor pressure deficit (SVPD) was calculated from temperature and RH to represent desiccation stress.
Survival Time Simulation: To harmonize disparate survival data formats (survival curves, mean/median longevity, survival proportions), individual mosquito survival times were simulated via Weibull and log-logistic models.
Pooled Survival Analysis: Stratified and mixed-effects Cox proportional hazards regression models were used to estimate hazard ratios (mortality risks) associated with temperature, SVPD, and nutritional factors.
Model Selection: SVPD was found to fit survival data better than RH or vapor pressure.
Sensitivity Analyses: Included testing model robustness by excluding individual studies and comparing results using only Weibull simulations.
Key Quantitative Findings
Parameter Ae. aegypti Ae. albopictus Notes
Temperature optimum (lowest mortality hazard) ~27.5 °C ~21.5 °C Ae. aegypti optimum higher than Ae. albopictus
Mortality risk trend Increases non-linearly away from optimum; sharp rise at higher temps Similar trend; possibly slightly better survival at lower temps Mortality rises rapidly at high temps for both species
Effect of desiccation (SVPD) Mortality hazard rises steeply from 0 to ~1 kPa SVPD, then more gradually Mortality hazard increases with SVPD but with less clear pattern Non-linear and temperature-dependent relationship
Species comparison (stratified model) Generally lower mortality risk than Ae. albopictus across most conditions Higher mortality risk compared to Ae. aegypti Differences not significant in mixed-effects model
Nutritional provisioning effects Provision of water, sugar, blood meals significantly reduces mortality risk Same as Ae. aegypti Provisioning modeled as binary present/absent
Qualitative and Contextual Insights
Humidity is a significant and temperature-dependent factor affecting adult female survival in Ae. aegypti, with more limited but suggestive evidence for Ae. albopictus.
Mortality risk increases sharply with desiccation stress (SVPD), especially at higher temperatures.
Ae. aegypti tends to have higher survival and a higher thermal optimum than Ae. albopictus, aligning with their geographic distributions—Ae. aegypti favors warmer, drier climates while Ae. albopictus tolerates cooler temperatures.
Provisioning of water and nutrients (sugar, blood) markedly improves survival, reflecting the importance of hydration and energy intake.
The findings support that humidity effects are underrepresented in current mosquito and disease transmission models, which often rely on simplistic or threshold-based mortality assumptions.
The use of SVPD (a measure of desiccation potential) rather than relative humidity or vapor pressure is more appropriate for modeling mosquito survival related to desiccation.
There is substantial unexplained variability among studies, likely due to unmeasured factors such as mosquito genetics, experimental protocols, and microclimatic conditions.
The majority of studies used laboratory settings and tropical/subtropical strains, with very limited data from arid or semi-arid climates, a critical gap given the importance of humidity fluctuations there.
Microclimatic variability and mosquito behavior (e.g., seeking humid refugia) may mitigate desiccation effects in the field, so laboratory results may overestimate mortality under natural conditions.
The study highlights the need for more field-based and arid region studies, and for models to incorporate nonlinear and interactive effects of temperature and humidity on mosquito survival.
Timeline Table: Study Selection and Analysis Process
Step Description
Literature search (Feb 2016) 1517 unique articles screened
Full text review 378 articles assessed for eligibility
Final inclusion 17 studies selected (16 lab, 1 semi-field)
Data extraction Survival data, temperature, humidity, nutrition, species, setting
Survival time simulation Weibull and log-logistic models used to harmonize survival data
Pooled survival analysis Stratified and mixed-effects Cox regression models
Sensitivity analyses Exclusion of individual studies, Weibull-only simulations
Model selection SVPD chosen as best humidity metric
Definitions and Key Terms
Term Definition
Aedes aegypti Primary mosquito vector of dengue, Zika, chikungunya, and yellow fever viruses
Aedes albopictus Secondary vector species with broader climatic tolerance, also transmits arboviruses
Saturation Vapor Pressure Deficit (SVPD) Difference between actual vapor pressure and saturation vapor pressure; a measure of drying potential/desiccation stress
Extrinsic Incubation Period (EIP) Time required for a virus to develop within the mosquito before it can be transmitted
Desiccation stress Physiological stress from water loss due to low humidity, impacting mosquito survival
Stratified Cox regression Survival analysis method allowing baseline hazards to vary by study
Mixed-effects Cox regression Survival analysis
Smart Summary
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