Increased temperatures reduce the vectorial capacity of Aedes mosquitoes for Zika virus

Aedes albopictus saliva contains a richer microbial community than the midgut

BACKGROUND

Past findings demonstrate that arthropods can egest midgut microbiota into the host skin leading to dual colonization of the vertebrate host with pathogens and saliva microbiome. A knowledge gap exists on how the saliva microbiome interacts with the pathogen in the saliva. To fill this gap, we need to first define the microbial composition of mosquito saliva.

METHODS

The current study aimed at analyzing and comparing the microbial profile of Aedes albopictus saliva and midgut as well as assessing the impact of Zika virus (ZIKV) infection on the midgut and saliva microbial composition. Colony-reared Ae. albopictus strains were either exposed to ZIKV infectious or noninfectious bloodmeal. At 14 ays postinfection, the 16S V3-V4 hypervariable rRNA region was amplified from midgut and saliva samples and sequenced on an Illumina MiSeq platform. The relative abundance and diversity of midgut and saliva microbial taxa were assessed.

RESULTS

We observed a richer microbial community in the saliva compared with the midgut, yet some of the microbial taxa were common in the midgut and saliva. ZIKV infection did not impact the microbial diversity of midgut or saliva. Further, we identified Elizabethkingia spp. in the Ae. albopictus saliva.

CONCLUSIONS

This study provides insights into the microbial community of the Ae. albopictus saliva as well as the influence of ZIKV infection on the microbial composition of its midgut and saliva. The identification of Elizabethkingia spp., an emerging pathogen of global health significance, in Ae. albopictus saliva is of medical importance. Future studies to assess the interactions between Ae. albopictus saliva microbiome and ZIKV could lead to novel strategies for developing transmission barrier tools.

Mechanistic modelling of within-mosquito viral dynamics: Insights into infection and dissemination patterns

Vector or host competence can be defined as the ability of an individual to become infected and subsequently transmit a pathogen. Assays to measure competence play a key part in the assessment of the factors affecting mosquito-borne virus transmission and of potential pathogen-blocking control tools for these viruses. For mosquitoes, competence for arboviruses can be measured experimentally and results are usually analysed using standard statistical approaches. Here we develop a mechanistic approach to studying within-mosquito virus dynamics that occur during vector competence experiments. We begin by developing a deterministic model of virus replication in the mosquito midgut and subsequent escape and replication in the hemocoel. We then extend this to a stochastic model to capture the between-individual variation observed in vector competence experiments. We show that the dose-response of the probability of mosquito midgut infection and variation in the dissemination rate can be explained by stochastic processes generated from a small founding population of virions, caused by a relatively low rate of virion infection of susceptible cells. We also show that comparing treatments or species in competence experiments by fitting mechanistic models could provide further insight into potential differences. Generally, our work adds to the growing body of literature emphasizing the importance of intrinsic stochasticity in biological systems.

Effects of Temperature on Blood Feeding and Activity Levels in the Tiger Mosquito, Aedes albopictus

Temperature has been shown to have profound effects on mosquito population dynamics and life history. Understanding these effects can provide insight into how mosquito populations and the diseases they transmit may vary across space and time and under the changes imposed by climate change. In this study, we evaluated how temperature affects the blood feeding and general activity patterns in the globally invasive mosquito species Aedes albopictus. We reared cohorts of Ae. albopictus from hatch through adulthood across three temperatures (26 °C, 29 °C, and 32 °C). The propensity of adult females to take a blood meal and the size of the blood meal were compared across temperatures. We also observed the overall activity levels of adult females over a 13.5 h period. At the highest temperature tested (32 °C), females were less likely to take a blood meal and were most active, as measured through frequency of movement. We postulate that our highest-temperature treatment imposes heat stress on adult female Ae. albopictus, where many abstain from blood feeding and increase movement in an attempt to escape the heat stress and find a more favorable resting location.

Temperature and transmission of chikungunya, dengue, and Zika viruses: A systematic review of experimental studies on Aedes aegypti and Aedes albopictus

Mosquito-borne viruses are leading causes of morbidity and mortality in many parts of the world. In recent years, modelling studies have shown that climate change strongly influences vector-borne disease transmission, particularly rising temperatures. As a result, the risk of epidemics has increased, posing a significant public health risk. This review aims to summarize all published laboratory experimental studies carried out over the years to determine the impact of temperature on the transmission of arboviruses by the mosquito vector. Given their high public health importance, we focus on dengue, chikungunya, and Zika viruses, which are transmitted by the mosquitoes Aedes aegypti and Aedes albopictus. Following PRISMA guidelines, 34 papers were included in this systematic review. Most studies found that increasing temperatures result in higher rates of infection, dissemination, and transmission of these viruses in mosquitoes, although several studies had differing findings. Overall, the studies reviewed here suggest that rising temperatures due to climate change would alter the vector competence of mosquitoes to increase epidemic risk, but that some critical research gaps remain.

Effects of constant temperature and daily fluctuating temperature on the transovarial transmission and life cycle of Aedes albopictus infected with Zika virus

Introduction

Numerous studies on the mosquito life cycle and transmission efficacy were performed under constant temperatures. Mosquito in wild, however, is not exposed to constant temperature but is faced with temperature variation on a daily basis.

Methods

In the present study, the mosquito life cycle and Zika virus transmission efficiency were conducted at daily fluctuating temperatures and constant temperatures. Aedes albopictus was infected with the Zika virus orally. The oviposition and survival of the infected mosquitoes and hatching rate, the growth cycle of larvae at each stage, and the infection rate (IR) of the progeny mosquitoes were performed at two constant temperatures (23°C and 31°C) and a daily temperature range (DTR, 23-31°C).

Results

It showed that the biological parameters of mosquitoes under DTR conditions were significantly different from that under constant temperatures. Mosquitoes in DTR survived longer, laid more eggs (mean number: 36.5 vs. 24.2), and had a higher hatching rate (72.3% vs. 46.5%) but a lower pupation rate (37.9% vs. 81.1%) and emergence rate (72.7% vs. 91.7%) than that in the high-temperature group (constant 31°C). When compared to the low-temperature group (constant 23°C), larvae mosquitoes in DTR developed faster (median days: 9 vs. 23.5) and adult mosquitoes carried higher Zika viral RNA load (median log₁₀ RNA copies/μl: 5.28 vs. 3.86). However, the temperature or temperature pattern has no effect on transovarial transmission.

Discussion

Those results indicated that there are significant differences between mosquito development and reproductive cycles under fluctuating and constant temperature conditions, and fluctuating temperature is more favorable for mosquitos' survival and reproduction. The data would support mapping and predicting the distribution of Aedes mosquitoes in the future and establishing an early warning system for Zika virus epidemics.

Association between Climate Factors and Dengue Fever in Asuncion, Paraguay: A Generalized Additive Model

Dengue fever has been endemic in Paraguay since 2009 and is a major cause of public-health-management-related burdens. However, Paraguay still lacks information on the association between climate factors and dengue fever. We aimed to investigate the association between climatic factors and dengue fever in Asuncion. Cumulative dengue cases from January 2014 to December 2020 were extracted weekly, and new cases and incidence rates of dengue fever were calculated. Climate factor data were aggregated weekly, associations between dengue cases and climate factors were analyzed, and variables were selected to construct our model. A generalized additive model was used, and the best model was selected based on Akaike information criteria. Piecewise regression analyses were performed for non-linear climate factors. Wind and relative humidity were negatively associated with dengue cases, and minimum temperature was positively associated with dengue cases when the temperature was less than 21.3 °C and negatively associated with dengue when greater than 21.3 °C. Additional studies on dengue fever in Asuncion and other cities are needed to better understand dengue fever.

Temperate Conditions Limit Zika Virus Genome Replication

Zika virus is a mosquito-borne flavivirus known to cause severe birth defects and neuroimmunological disorders. We have previously demonstrated that mosquito transmission of Zika virus decreases with temperature. While transmission was optimized at 29°C, it was limited at cool temperatures (<22°C) due to poor virus establishment in the mosquitoes. Temperature is one of the strongest drivers of vector-borne disease transmission due to its profound effect on ectothermic mosquito vectors, viruses, and their interaction. Although there is substantial evidence of temperature effects on arbovirus replication and dissemination inside mosquitoes, little is known about whether temperature affects virus replication directly or indirectly through mosquito physiology. In order to determine the mechanisms behind temperature-induced changes in Zika virus transmission potential, we investigated different steps of the virus replication cycle in mosquito cells (C6/36) at optimal (28°C) and cool (20°C) temperatures. We found that the cool temperature did not alter Zika virus entry or translation, but it affected genome replication and reduced the amount of double-stranded RNA replication intermediates. If replication complexes were first formed at 28°C and the cells were subsequently shifted to 20°C, the late steps in the virus replication cycle were efficiently completed. These data suggest that cool temperature decreases the efficiency of Zika virus genome replication in mosquito cells. This phenotype was observed in the Asian lineage of Zika virus, while the African lineage Zika virus was less restricted at 20°C. IMPORTANCE With half of the human population at risk, arboviral diseases represent a substantial global health burden. Zika virus, previously known to cause sporadic infections in humans, emerged in the Americas in 2015 and quickly spread worldwide. There was an urgent need to better understand the disease pathogenesis and develop therapeutics and vaccines, as well as to understand, predict, and control virus transmission. In order to efficiently predict the seasonality and geography for Zika virus transmission, we need a deeper understanding of the host-pathogen interactions and how they can be altered by environmental factors such as temperature. Identifying the step in the virus replication cycle that is inhibited under cool conditions can have implications in modeling the temperature suitability for arbovirus transmission as global environmental patterns change. Understanding the link between pathogen replication and environmental conditions can potentially be exploited to develop new vector control strategies in the future.

Microbial Composition in Larval Water Enhances Aedes aegypti Development but Reduces Transmissibility of Zika Virus

Arthropod-borne viruses comprise a significant global disease burden. Surveillance and mitigation of arboviruses like Zika virus (ZIKV) require accurate estimates of transmissibility by vector mosquitoes. Although Aedes species mosquitoes are established as competent ZIKV vectors, differences in experimental protocols across studies prevent direct comparisons of relative transmissibility. An understudied factor complicating these comparisons is differential environmental microbiota exposures, where most vector competence studies use mosquitoes reared in laboratory tap water, which does not represent the microbial complexity of environmental water where wild larvae develop. We simulated natural larval development by rearing Californian Aedes aegypti larvae with microbes obtained from cemetery headstone water compared to conventional tap water. A. aegypti larvae reared in environmental cemetery water pupated 3 days faster and at higher rates. Mosquitoes reared in environmental water were less competent vectors of ZIKV than laboratory water-reared A. aegypti, as evidenced by significantly reduced infection and transmission rates. Microbiome comparisons of laboratory water- and environment water-reared mosquitoes and their rearing water showed significantly higher bacterial diversity in environment water. Despite this pattern, corresponding differences in bacterial diversity were not consistently observed between the respective adult mosquitoes. We also observed that the microbial compositions of adult mosquitoes differed more by whether they ingested a bloodmeal than by larval water type. Together, these results highlight the role of transient microbes in the larval environment in modulating A. aegypti vector competence for ZIKV. Laboratory vector competence likely overestimates the true transmissibility of arboviruses like ZIKV when conventional laboratory water is used for rearing. IMPORTANCE We observed that A. aegypti mosquitoes reared in water from cemetery headstones instead of the laboratory tap exhibited a reduced capacity to become infected with and transmit Zika virus. Water from the environment contained more bacterial species than tap water, but these bacteria were not consistently detected in adult mosquitoes. Our results suggest that rearing mosquito larvae in water collected from local environments as opposed to laboratory tap water, as is conventional, could provide a more realistic assessment of ZIKV vector competence since it better recapitulates the natural environment in which larvae develop. Given that laboratory vector competence is used to define the species to target for control, the use of environmental water to rear larvae could better approximate the microbial exposures of wild mosquitoes, lessening the potential for overestimating ZIKV transmission risk. These studies raise the question of whether rearing larvae in natural water sources also reduces vector competence for other mosquito-borne viruses.

The ecophysiological plasticity of Aedes aegypti and Aedes albopictus concerning overwintering in cooler ecoregions is driven by local climate and acclimation capacity

Aedes aegypti and Aedes albopictus transmit diseases such as dengue, and are of major public health concern. Driven by climate change and global trade/travel both species have recently spread to new tropic/subtropic regions and Ae. albopictus also to temperate ecoregions. The capacity of both species to adapt to new environments depends on their ecophysiological plasticity, which is the width of functional niches where a species can survive. Mechanistic distribution models often neglect to incorporate ecophysiological plasticity especially in regards to overwintering capacity in cooler habitats. To portray the ecophysiological plasticity concerning overwintering capability, we conducted temperature experiments with multiple populations of both species originating from an altitudinal gradient in South Asia and tested as follows: the cold tolerance of eggs (-2 °C- 8 days and - 6 °C- 2 days) without and with an experimental winter onset (acclimation: 10 °C- 60 days), differences between a South Asian and a European Ae. albopictus population and the temperature response in life cycles (13 °C, 18 °C, 23 °C, 28 °C). Ecophysiological plasticity in overwintering capacity in Ae. aegypti is high in populations originating from low altitude and in Ae. albopictus populations from high altitude. Overall, ecophysiological plasticity is higher in Ae. albopictus compared to Ae. aegypti. In both species acclimation and in Ae. albopictus temperate continental origin had a huge positive effect on survival. Our results indicate that future mechanistic prediction models can include data on winter survivorship of both, tropic and subtropic Ae. aegypti, whereas for Ae. albopictus this depends on the respective temperate, tropical region the model is focusing on. Future research should address cold tolerance in multiple populations worldwide to evaluate the full potential of the ecophysiological plasticity in the two species. Furthermore, we found that Ae. aegypti can survive winter cold especially when acclimated and will probably further spread to colder ecoregions driven by climate change.

A Systematic Review of the Effects of Temperature on Anopheles Mosquito Development and Survival: Implications for Malaria Control in a Future Warmer Climate

The rearing temperature of the immature stages can have a significant impact on the life-history traits and the ability of adult mosquitoes to transmit diseases. This review assessed published evidence of the effects of temperature on the immature stages, life-history traits, insecticide susceptibility, and expression of enzymes in the adult Anopheles mosquito. Original articles published through 31 March 2021 were systematically retrieved from Scopus, Google Scholar, Science Direct, PubMed, ProQuest, and Web of Science databases. After applying eligibility criteria, 29 studies were included. The review revealed that immature stages of An. arabiensis were more tolerant (in terms of survival) to a higher temperature than An. funestus and An. quadriannulatus. Higher temperatures resulted in smaller larval sizes and decreased hatching and pupation time. The development rate and survival of An. stephensi was significantly reduced at a higher temperature than a lower temperature. Increasing temperatures decreased the longevity, body size, length of the gonotrophic cycle, and fecundity of Anopheles mosquitoes. Higher rearing temperatures increased pyrethroid resistance in adults of the An. arabiensis SENN DDT strain, and increased pyrethroid tolerance in the An. arabiensis SENN strain. Increasing temperature also significantly increased Nitric Oxide Synthase (NOS) expression and decreased insecticide toxicity. Both extreme low and high temperatures affect Anopheles mosquito development and survival. Climate change could have diverse effects on Anopheles mosquitoes. The sensitivities of Anopeheles mosquitoes to temperature differ from species to species, even among the same complex. Notwithstanding, there seem to be limited studies on the effects of temperature on adult life-history traits of Anopheles mosquitoes, and more studies are needed to clarify this relationship.

Temperate conditions restrict Japanese encephalitis virus infection to the mid-gut and prevents systemic dissemination in Culex pipiens mosquitoes

Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, is the main cause of viral encephalitis in Asia. However, with changing climate JEV has the potential to emerge in novel temperate regions. Here, we have assessed the vector competence of the temperate mosquito Culex pipiens f. pipiens to vector JEV genotype III at temperatures representative of those experienced, or predicted in the future during the summer months, in the United Kingdom. Our results show that Cx. pipiens is susceptible to JEV infection at both temperatures. In addition, at 25 °C, JEV disseminated from the midgut and was recovered in saliva samples, indicating the potential for transmission. At a lower temperature, 20 °C, following an incubation period of fourteen days, there were reduced levels of JEV dissemination and virus was not detected in saliva samples. The virus present in the bodies of these mosquitoes was restricted to the posterior midgut as determined by microscopy and viable virus was successfully recovered. Apart from the influence on virus dissemination, mosquito mortality was significantly increased at the higher temperature. Overall, our results suggest that temperature is a critical factor for JEV vector competence and infected-mosquito survival. This may in turn influence the vectorial capacity of Cx. pipiens to vector JEV genotype III in temperate areas.

Vertebrate-Aedes aegypti and Culex quinquefasciatus (Diptera)-arbovirus transmission networks: Non-human feeding revealed by meta-barcoding and next-generation sequencing

Background

Aedes aegypti mosquito-borne viruses including Zika (ZIKV), dengue (DENV), yellow fever (YFV), and chikungunya (CHIKV) have emerged and re-emerged globally, resulting in an elevated burden of human disease. Aedes aegypti is found worldwide in tropical, sub-tropical, and temperate areas. The characterization of mosquito blood meals is essential to understand the transmission dynamics of mosquito-vectored pathogens.

Methodology/principal findings

Here, we report Ae. aegypti and Culex quinquefasciatus host feeding patterns and arbovirus transmission in Northern Mexico using a metabarcoding-like approach with next-generation deep sequencing technology. A total of 145 Ae. aegypti yielded a blood meal analysis result with 107 (73.8%) for a single vertebrate species and 38 (26.2%) for two or more. Among the single host blood meals for Ae. aegypti, 28.0% were from humans, 54.2% from dogs, 16.8% from cats, and 1.0% from tortoises. Among those with more than one species present, 65.9% were from humans and dogs. For Cx. quinquefasciatus, 388 individuals yielded information with 326 (84%) being from a single host and 63 (16.2%) being from two or more hosts. Of the single species blood meals, 77.9% were from dogs, 6.1% from chickens, 3.1% from house sparrows, 2.4% from humans, while the remaining 10.5% derived from other 12 host species. Among those which had fed on more than one species, 11% were from dogs and humans, and 89% of other host species combinations. Forage ratio analysis revealed dog as the most over-utilized host by Ae. aegypti (= 4.3) and Cx. quinquefasciatus (= 5.6) and the human blood index at 39% and 4%, respectively. A total of 2,941 host-seeking female Ae. aegypti and 3,536 Cx. quinquefasciatus mosquitoes were collected in the surveyed area. Of these, 118 Ae. aegypti pools and 37 Cx. quinquefasciatus pools were screened for seven arboviruses (ZIKV, DENV 1–4, CHIKV, and West Nile virus (WNV)) using qRT-PCR and none were positive (point prevalence = 0%). The 95%-exact upper limit confidence interval was 0.07% and 0.17% for Ae. aegypti and Cx. quinquefasciatus, respectively

Conclusions/significance

The low human blood feeding rate in Ae. aegypti, high rate of feeding on mammals by Cx. quinquefasciatus, and the potential risk to transmission dynamics of arboviruses in highly urbanized areas of Northern Mexico is discussed.

Elucidating arbovirus-vector-host contact networks is critical to understand and control mosquito-borne virus transmission, including pathogens such as ZIKV, DENV 1–4, CHIKV, and WNV. Here, we report the results of metabarcoding of blood meals of two primary pathogen mosquito vectors, Aedes aegypti and Culex quinquefasciatus. We found limited human blood feeding by Ae. aegypti and high preference for feeding on mammals by Cx. quinquefasciatus. Interestingly, blood meal analysis revealed dogs as the most utilized host for both vector species suggesting the potential for zooprophylaxis for human-amplified urban arboviruses. Pools of these vector species were tested for seven arboviruses and all were negative. We calculated vectorial capacity to discuss the potential risk and transmission dynamics of pathogens transmitted by these two important vectors in an urban location in Northern Mexico.

Increase in temperature enriches heat tolerant taxa in Aedes aegypti midguts

Insect midgut microbial symbionts have been considered as an integral component in thermal adaptation due to their differential thermal sensitivity. Altered midgut microbial communities can influence both insect physiology and competence for important vector-borne pathogens. This study sought to gain insights into how Aedes aegypti midgut microbes and life history traits are affected by increase in baseline diurnal temperature. Increase in temperature resulted in the enrichment of specific taxa with Bacillus being the most enriched. Bacillus is known to be heat tolerant. It also resulted in a dissimilar microbial assemblage (Bray-Curtis Index, PERMANOVA, F = 2.2063; R2 = 0.16706; P = 0.002) and reduced survivorship (Log-rank [Mantel-Cox] test, Chi-square = 35.66 df = 5, P < 0.0001). Blood meal intake resulted in proliferation of pathogenic bacteria such as Elizabethkingia in the midgut of the mosquitoes. These results suggest that alteration of temperature within realistic parameters such as 2 °C for Ae. aegypti in nature may impact the midgut microbiome favoring specific taxa that could alter mosquito fitness, adaptation and vector-pathogen interactions.

Zika Virus Infection Results in Biochemical Changes Associated With RNA Editing, Inflammatory and Antiviral Responses in Aedes albopictus

Rapid and significant range expansion of both the Zika virus (ZIKV) and its Aedes vector species has resulted in the declaration of ZIKV as a global health threat. Successful transmission of ZIKV by its vector requires a complex series of interactions between these entities including the establishment, replication and dissemination of the virus within the mosquito. The metabolic conditions within the mosquito tissues play a critical role in mediating the crucial processes of viral infection and replication and represent targets for prevention of virus transmission. In this study, we carried out a comprehensive metabolomic phenotyping of ZIKV infected and uninfected Ae. albopictus by untargeted analysis of primary metabolites, lipids and biogenic amines. We performed a comparative metabolomic study of infection state with the aim of understanding the biochemical changes resulting from the interaction between the ZIKV and its vector. We have demonstrated that ZIKV infection results in changes to the cellular metabolic environment including a significant enrichment of inosine and pseudo-uridine (Ψ) levels which may be associated with RNA editing activity. In addition, infected mosquitoes demonstrate a hypoglycemic phenotype and show significant increases in the abundance of metabolites such as prostaglandin H2, leukotriene D4 and protoporphyrinogen IX which are associated with antiviral activity. These provide a basis for understanding the biochemical response to ZIKV infection and pathology in the vector. Future mechanistic studies targeting these ZIKV infection responsive metabolites and their associated biosynthetic pathways can provide inroads to identification of mosquito antiviral responses with infection blocking potential.

Contrasted transmission efficiency of Zika virus strains by mosquito species Aedes aegypti, Aedes albopictus and Culex quinquefasciatus from Reunion Island

BACKGROUND

Zika virus (ZIKV) is a mosquito-borne flavivirus that recently emerged in the South Pacific islands and Americas where unprecedented outbreaks were reported. Although Aedes aegypti is considered to be the main vector for ZIKV, other mosquito species have been shown to be potential vectors and differences in vector competence with respect to mosquito strain and ZIKV strain have been demonstrated. In this study we compared the vector competence of three mosquito species Aedes albopictus, Ae. aegypti and Culex quinquefasciatus from Reunion Island for three ZIKV strains.

METHODS

Five mosquito strains (2 strains of Ae. albopictus, 1 of Ae. aegypti and 2 of Cx. quinquefasciatus) were exposed to three ZIKV strains: one African strain (Dak84) and two Asian strains (PaRi_2015 and MAS66). The vector competence parameters (infection rate, dissemination efficiency and transmission efficiency) and viral loads were examined at 14 and 21 days post-infection.

RESULTS

The two Cx. quinquefasciatus strains did not become infected and were therefore unable to either disseminate or transmit any of the three ZIKV strains. Aedes albopictus and Ae. aegypti strains were poorly competent for the two Asian ZIKV strains, while both mosquito species displayed higher infection rates, dissemination and transmission efficiencies for the African ZIKV Dak84 strain. However, this African ZIKV strain was better transmitted by Ae. aegypti as compared to Ae. albopictus.

CONCLUSIONS

Our results show that both Ae. albopictus and Ae. aegypti, from Reunion Island, are more likely to be competent for ZIKV in contrast to Cx. quinquefasciatus which appeared refractory to all tested ZIKV strains. This improves our understanding of the role of mosquito species in the risk of the ZIKV emergence on Reunion Island.

Age-structured vectorial capacity reveals timing, not magnitude of within-mosquito dynamics is critical for arbovirus fitness assessment

Background

Transmission dynamics of arboviruses like Zika virus are often evaluated by vector competence (the proportion of infectious vectors given exposure) and the extrinsic incubation period (EIP, the time it takes for a vector to become infectious), but vector age is another critical driver of transmission dynamics. Vectorial capacity (VC) is a measure of transmission potential of a vector-pathogen system, but how these three components, EIP, vector competence and vector age, affect VC in concert still needs study.

Methods

The interaction of vector competence, EIP, and mosquito age at the time of infection acquisition (Age_acquisition) was experimentally measured in an Aedes aegypti-ZIKV model system, as well as the age-dependence of probability of survival and the willingness to bite. An age-structured vectorial capacity framework (VC_age) was then developed using both EIP_Min and EIP_Max, defined as the time to first observed minimum proportion of transmitting mosquitoes and the time to observed maximum proportion of transmitting mosquitoes.

Results

The within-mosquito dynamics of vector competence/EIP were not significant among treatments where mosquitoes were exposed at different ages. However, VC_age revealed: (i) age-dependence in vector-virus interactions is important for transmission success; (ii) lower vector competence but at shorter EIPs was sufficient for transmission perpetuation; and (iii) R₀ may be overestimated by using non-age-structured VC.

Conclusions

The results indicate that ultimately the temporal component of the virus-vector dynamics is most critical, especially when exposure occurred at advanced mosquito age. While our study is limited to a single virus-vector system, and a multitude of other factors affect both vector competence and mosquito mortality, our methods can be extrapolated to these other scenarios. Results indicate that how ‘highly’ or ‘negligibly’ competent vectors are categorized may need adjustment.

Not Just from Blood: Mosquito Nutrient Acquisition from Nectar Sources

Anthropophilic female mosquitoes are well known for their strong attraction to human hosts, but plant nectar is a common energy source in their diets. When sugar sources are scarce, female mosquitoes of some species can compensate by taking larger and more frequent blood meals. Male mosquitoes are exclusively dependent on plant nectar or alternative sugar sources. Plant preference is likely driven by an innate attraction that may be enhanced by experience, as mosquitoes learn to recognize available sugar rewards. Nectar-seeking involves the integration of at least three sensory systems: olfaction, vision and taste. The prevention of vector-borne illnesses, the determination of the mosquitoes' ecological role, and the design of efficient sugar-baited traps will all benefit from understanding the molecular basis of nectar-seeking.