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1. Transmission of West Nile and five other temperate mosquito-borne viruses peaks at temperatures between 23°C and 26°C

   https://doi.org/10.7554/eLife.58511  

   Shocket, Marta S ; Verwillow, Anna B ; Numazu, Mailo G ; Slamani, Hani ; Cohen, Jeremy M ; El Moustaid, Fadoua ; Rohr, Jason ; Johnson, Leah R ; Mordecai, Erin A ( September 2020 , eLife)

   null (Ed.)

   The temperature-dependence of many important mosquito-borne diseases has never been quantified. These relationships are critical for understanding current distributions and predicting future shifts from climate change. We used trait-based models to characterize temperature-dependent transmission of 10 vector–pathogen pairs of mosquitoes ( Culex pipiens , Cx. quinquefascsiatus , Cx. tarsalis , and others) and viruses (West Nile, Eastern and Western Equine Encephalitis, St. Louis Encephalitis, Sindbis, and Rift Valley Fever viruses), most with substantial transmission in temperate regions. Transmission is optimized at intermediate temperatures (23–26°C) and often has wider thermal breadths (due to cooler lower thermal limits) compared to pathogens with predominately tropical distributions (in previous studies). The incidence of human West Nile virus cases across US counties responded unimodally to average summer temperature and peaked at 24°C, matching model-predicted optima (24–25°C). Climate warming will likely shift transmission of these diseases, increasing it in cooler locations while decreasing it in warmer locations. 

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2. Not all mosquitoes are created equal: A synthesis of vector competence experiments reinforces virus associations of Australian mosquitoes

   https://doi.org/10.1371/journal.pntd.0010768  

   Kain, Morgan P. ; Skinner, Eloise B. ; Athni, Tejas S. ; Ramirez, Ana L. ; Mordecai, Erin A. ; van den Hurk, Andrew F. ( October 2022 , PLOS Neglected Tropical Diseases)

   Brackney, Doug E. (Ed.)

   The globalization of mosquito-borne arboviral diseases has placed more than half of the human population at risk. Understanding arbovirus ecology, including the role individual mosquito species play in virus transmission cycles, is critical for limiting disease. Canonical virus-vector groupings, such as Aedes - or Culex -associated flaviviruses, have historically been defined using virus detection in field-collected mosquitoes, mosquito feeding patterns, and vector competence, which quantifies the intrinsic ability of a mosquito to become infected with and transmit a virus during a subsequent blood feed. Herein, we quantitatively synthesize data from 68 laboratory-based vector competence studies of 111 mosquito-virus pairings of Australian mosquito species and viruses of public health concern to further substantiate existing canonical vector-virus groupings and quantify variation within these groupings. Our synthesis reinforces current canonical vector-virus groupings but reveals substantial variation within them. While Aedes species were generally the most competent vectors of canonical “ Aedes -associated flaviviruses” (such as dengue, Zika, and yellow fever viruses), there are some notable exceptions; for example, Aedes notoscriptus is an incompetent vector of dengue viruses. Culex spp. were the most competent vectors of many traditionally Culex -associated flaviviruses including West Nile, Japanese encephalitis and Murray Valley encephalitis viruses, although some Aedes spp. are also moderately competent vectors of these viruses. Conversely, many different mosquito genera were associated with the transmission of the arthritogenic alphaviruses, Ross River, Barmah Forest, and chikungunya viruses. We also confirm that vector competence is impacted by multiple barriers to infection and transmission within the mesenteron and salivary glands of the mosquito. Although these barriers represent important bottlenecks, species that were susceptible to infection with a virus were often likely to transmit it. Importantly, this synthesis provides essential information on what species need to be targeted in mosquito control programs. 

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3. Effect of Temperature on Mosquito Olfaction

   https://doi.org/10.1093/icb/icad066  

   Lahondère, Chloé ; Vinauger, Clément ; Liaw, Jessica_E ; Tobin, Kennedy_K_S ; Joiner, Jillian_M ; Riffell, Jeffrey_A ( June 2023 , Integrative And Comparative Biology)

   Mosquitoes use a wide range of cues to find a host to feed on, eventually leading to the transmission of pathogens. Among them, olfactory cues (e.g., host-emitted odors, including CO2, and skin volatiles) play a central role in mediating host-seeking behaviors. While mosquito olfaction can be impacted by many factors, such as the physiological state of the insect (e.g., age, reproductive state), the impact of environmental temperature on the olfactory system remains unknown. In this study, we quantified the behavioral responses of Aedes aegypti mosquitoes, vectors of dengue, yellow fever, and Zika viruses, among other pathogens, to host and plant-related odors under different environmental temperatures.

    

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4. Climate predicts geographic and temporal variation in mosquito-borne disease dynamics on two continents

   https://doi.org/10.1038/s41467-021-21496-7  

   Caldwell, Jamie M. ; LaBeaud, A. Desiree ; Lambin, Eric F. ; Stewart-Ibarra, Anna M. ; Ndenga, Bryson A. ; Mutuku, Francis M. ; Krystosik, Amy R. ; Ayala, Efraín Beltrán ; Anyamba, Assaf ; Borbor-Cordova, Mercy J. ; et al ( December 2021 , Nature Communications)

   null (Ed.)

   Abstract Climate drives population dynamics through multiple mechanisms, which can lead to seemingly context-dependent effects of climate on natural populations. For climate-sensitive diseases, such as dengue, chikungunya, and Zika, climate appears to have opposing effects in different contexts. Here we show that a model, parameterized with laboratory measured climate-driven mosquito physiology, captures three key epidemic characteristics across ecologically and culturally distinct settings in Ecuador and Kenya: the number, timing, and duration of outbreaks. The model generates a range of disease dynamics consistent with observed Aedes aegypti abundances and laboratory-confirmed arboviral incidence with variable accuracy (28–85% for vectors, 44–88% for incidence). The model predicted vector dynamics better in sites with a smaller proportion of young children in the population, lower mean temperature, and homes with piped water and made of cement. Models with limited calibration that robustly capture climate-virus relationships can help guide intervention efforts and climate change disease projections. 

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5. Temperature impacts the environmental suitability for malaria transmission by Anopheles gambiae and Anopheles stephensi

   https://doi.org/10.1002/ecy.3685  

   Villena, Oswaldo C. ; Ryan, Sadie J. ; Murdock, Courtney C. ; Johnson, Leah R. ( June 2022 , Ecology)

   Extrinsic environmental factors influence the spatiotemporal dynamics of many organisms, including insects that transmit the pathogens responsible for vector‐borne diseases (VBDs). Temperature is an especially important constraint on the fitness of a wide variety of ectothermic insects. A mechanistic understanding of how temperature impacts traits of ectotherms, and thus the distribution of ectotherms and vector‐borne infections, is key to predicting the consequences of climate change on transmission of VBDs like malaria. However, the response of transmission to temperature and other drivers is complex, as thermal traits of ectotherms are typically nonlinear, and they interact to determine transmission constraints. In this study, we assess and compare the effect of temperature on the transmission of two malaria parasites,Plasmodium falciparumandPlasmodium vivax, by two malaria vector species,Anopheles gambiaeandAnopheles stephensi. We model the nonlinear responses of temperature dependent mosquito and parasite traits (mosquito development rate, bite rate, fecundity, proportion of eggs surviving to adulthood, vector competence, mortality rate, and parasite development rate) and incorporate these traits into a suitability metric based on a model for the basic reproductive number across temperatures. Our model predicts that the optimum temperature for transmission suitability is similar for the four mosquito–parasite combinations assessed in this study, but may differ at the thermal limits. More specifically, we found significant differences in the upper thermal limit between parasites spread by the same mosquito (A. stephensi) and between mosquitoes carryingP. falciparum. In contrast, at the lower thermal limit the significant differences were primarily between the mosquito species that both carried the same pathogen (e.g.,A. stephensiandA. gambiaeboth withP. falciparum). Using prevalence data, we show that the transmission suitability metric calculated from our mechanistic model is consistent with observedP. falciparumprevalence in Africa and Asia but is equivocal forP. vivaxprevalence in Asia, and inconsistent withP. vivaxprevalence in Africa. We mapped risk to illustrate the number of months various areas in Africa and Asia predicted to be suitable for malaria transmission based on this suitability metric. This mapping provides spatially explicit predictions for suitability and transmission risk.

    

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