About

Michael Riehle is a professor leading the Riehle lab, which conducts research related to mosquitoes. The lab focuses on conducting mosquito research, and interested students are encouraged to contact him for opportunities in this field. His work involves understanding mosquito biology and behavior, contributing to the broader field of vector research. The lab has a history of training undergraduate students, graduate students, post-doctoral fellows, and research technicians, indicating a strong commitment to education and research in entomology and vector biology.

Research topics

• Ecology
• Biology
• Genetics
• Virology
• Zoology
• Immunology
• Biochemistry
• Statistics
• Cell biology
• Microbiology

Selected publications

• Impacts of ground-based ULV pyrethroid sprays on abundance and age structure of the Zika vector, <i>Aedes aegypti</i> (Diptera: Culicidae), in urban Arizona

  Journal of Medical Entomology · 2025-04-03

  articleSenior author

  Aedes aegypti (L.), the primary mosquito vector of arboviruses such as dengue and Zika, has a global distribution that includes the southern United States. Control of this peridomestic mosquito is challenging. Ultra-low volume (ULV) pyrethroid sprays are commonly used against adult mosquitoes to break transmission during a disease outbreak, although efficacy data are limited. This study examined the impacts of ULV sprays on Ae. aegypti vectorial capacity as measured by vector abundance and age structure in two cities in Maricopa County, AZ with robust Ae. aegypti populations and a well-developed vector management program. We assessed impacts of routine ULV applications conducted by Maricopa Vector Control Division during the summer rainy seasons of 2017 to 2019 to determine whether existing practices mainly targeting Culex spp. also suppressed Ae. aegypti. The insecticide formulations applied for Culex spp. control (Duet and Permanone 30-30) did not affect Ae. aegypti abundance, but Duet applications slightly reduced female mosquito age. Deltagard, the insecticide product used specifically against Ae. aegypti, was only applied three times in 2018 over small areas, so efficacy assessment was difficult. Deltagard was associated with a small decline in Ae. aegypti abundance. CDC bottle bioassays of Ae. aegypti collected in the study area showed resistance to permethrin and deltamethrin. Overall, the lack of significant mosquito population suppression or age structure changes after insecticide applications suggest that current tools used by Maricopa Vector Control Division are unlikely to effectively control Ae. aegypti populations in the event of a disease outbreak.

  PublisherDOI

• Evaluating Associations Between Drought and West Nile Virus Epidemics: A Systematic Review

  Microorganisms · 2025-12-15

  articleOpen access

  Human West Nile virus (WNV) infections can have severe neurological health effects, especially among those over 50 years of age. As changes in weather patterns lead to more frequent and intense droughts, there is a public health need for improved understanding of drought associated WNV risks. While multiple studies have reported an association between drought conditions and human WNV cases, this information has not yet been synthesized systematically across studies. Our review aims to evaluate the existing evidence of an association between drought and human WNV cases while considering the impacts of different study regions, methodological approaches, drought metrics, and WNV case definitions. We conducted a systematic literature search of peer-reviewed epidemiological studies that examined a potential association between drought and human WNV cases. Our inclusion criteria targeted studies that employed measures of drought beyond precipitation and reported effect estimates along with measures of error. The literature search and screening process resulted in the inclusion of nine papers with study periods spanning from 1999 to 2018. The included peer-reviewed publications employed a wide variety of study designs and methods, such as linear mixed-effects models, generalized linear models using simultaneous autoregression, generalized additive models, Bayesian model averaging, and a case-crossover design using conditional logistic regression models. We summarize the key findings and provide study quality evaluations for each of the nine included studies. Studies that analyzed drought indices averaged over a seasonal period of three to four months reported positive associations between drought and WNV. However, studies that analyzed drought indicator variables averaged over weekly periods of time had less consistent results. We discuss potential mechanisms underlying the observed associations between drought and human WNV cases.

  PublisherOA PDFDOI

• Characterization of the Sodium Multi-Vitamin Transporter in the Mosquito Anopheles stephensi and Its Capacity to Mobilize Pantothenate and Biotin

  Biomolecules · 2025-01-03 · 2 citations

  articleOpen accessSenior authorCorresponding

  Pantothenate (Pan), or vitamin B5, is essential for the synthesis of co-enzyme A (CoA), acetyl-CoA, and numerous downstream physiological processes. We previously demonstrated that Pan is not only essential for mosquito survival, but also for the development of malaria parasites within the mosquito, suggesting that targeting Pan and CoA biosynthesis may be a novel approach for malaria control. However, little is known about how Pan is acquired and mobilized within the mosquito. In this work, we examined Pan levels in the important human malaria vector Anopheles stephensi, including the abundance of Pan during immature development and adulthood. We also assessed the distribution of Pan in various adult tissues and examined the impact of provisioning Pan to the mosquito via a sugar or blood meal on mosquito survival and reproduction. Furthermore, we examined how Pan was mobilized in the mosquito via a putative Pan transporter, the A. stephensi sodium multi-vitamin transporter. We demonstrated that this transporter is capable of mobilizing both Pan and biotin (vitamin B7) in a dose dependent manner. We also assessed the distribution of A. stephensi sodium multi-vitamin transporter in the mosquito and its capacity to transport vitamins. This work establishes the basic physiology of Pan uptake and mobilization in the mosquito, providing essential information for Pan based malaria control strategies.

  PublisherOA PDFDOI

• Structural features of outdoor latrines influence the abundance of Anopheles gambiae s.l. and Culex quinquefasciatus in a village in Kisumu County, western Kenya

  Parasites & Vectors · 2025-08-27 · 1 citations

  articleOpen access

  BACKGROUND: Malaria remains a leading cause of mortality in Kenya, despite concerted efforts in malaria vector control. Reducing outdoor transmission is a key factor in addressing residual malaria. Outdoor latrines are characterized as semi-sheltered structures with humid environments, which may provide an ideal resting site for Anopheles species to feed on human blood and subsequently rest. This study aimed to quantify the abundance of adult mosquitoes in houses and outdoor latrines, as well as explore the environmental factors associated with mosquito abundance. METHODS: Monthly mosquito sampling was conducted in 50 houses and their corresponding outdoor latrines using Prokopack aspirators from July 2023 to April 2024. Household interviews were conducted concurrently to collect data on the number of individuals sleeping in the houses and the quantity of bednets used within the households. In addition, blood meal sources were identified through polymerase chain reaction (PCR) analysis of blood-fed mosquitoes collected from December 2023 to April 2024. RESULTS: Among anopheline species, the An. funestus group was the most common, followed by An. gambiae s.l. in both houses and latrines. In anophelines, the human blood index was 50.0% (n = 15) in houses and 33.3% (n = 4) in latrines, while bovine blood was 60.0% (n = 18) and 66.7% (n = 8), respectively. Ventilated improved pit (VIP) latrines were associated with a 61% decrease in An. gambiae s.l. abundance (adjusted incidence rate ratio [aIRR] = 0.39, 95% confidence interval [CI] = 0.16-0.96) and a 62% decrease in Culex quinquefasciatus abundance (aIRR = 0.38, 95% CI = 0.24-0.60), compared with pit latrines. The presence of a bathing space in latrines was associated with a 23% increase in Cx. quinquefasciatus abundance (aIRR = 1.88, 95% CI = 1.23-2.89) compared with latrines without a bathing space. There was an inverse association between the number of individuals using the latrines and Cx. quinquefasciatus abundance (aIRR = 0.93, 95% CI = 0.89-0.97). CONCLUSIONS: VIP latrines were associated with a lower abundance of An. gambiae s.l. and Cx. quinquefasciatus compared with pit latrines, whereas the presence of a bathing space in latrines was associated with a higher abundance of Cx. quinquefasciatus compared with latrines without bathing spaces. Integrative public health programs that promote the construction of VIP latrines as a low-cost intervention may provide co-benefits for both sanitation and vector control.

  PublisherOA PDFDOI

• Pantothenate regulates feeding and reproduction in the malaria vector Anopheles stephensi, with patterns dependent on supplementation scheme and parental nutrition

  Parasites & Vectors · 2025-08-04

  articleOpen access

  BACKGROUND: Pantothenate (Pan), or vitamin B5, is the substrate for biosynthesis of coenzyme A (CoA), an essential cellular cofactor involved in many metabolic processes. Our previous studies demonstrated that Pan availability influences a broad range of traits across multiple species, including malaria parasite development in the mosquito Anopheles stephensi. Accordingly, restricting Pan availability during parasite development may be a viable strategy for malaria control. However, the physiological roles of Pan in A. stephensi remain unclear. In these studies, we investigated the effects of Pan supplementation on this globally important malaria vector. METHODS: Female A. stephensi were supplemented with Pan via either water, which, similar to plant nectar, is directed to the crop and then slowly released into the midgut, or blood, which transits directly to the midgut for digestion. The effects of provisioning on subsequent blood feeding behavior, reproduction, and offspring sex ratio were assessed. We evaluated these traits across multiple generations, with and without additional supplementation of offspring. RESULTS: Our findings revealed that Pan regulates vectorially important traits in concentration-, delivery-, and age-dependent ways. The greatest effects of Pan provisioning were on reproduction. The unsupplemented offspring of mothers supplemented with Pan via water exhibited increased fecundity, indicating transgenerational effects from supplemented mothers. However, when Pan was provisioned in blood, only mothers and their supplemented offspring exhibited altered reproduction. CONCLUSIONS: Our work establishes the importance of Pan in A. stephensi reproduction and provides a foundation for investigating the transgenerational effects of Pan and CoA on mosquito physiology. These observations suggest that targeting Pan-CoA biology in Anopheles spp. could provide opportunities for novel mosquito control strategies.

  PublisherOA PDFDOI

• Chemical Probes to Interrogate the Extreme Environment of Mosquito Larval Guts

  Journal of the American Chemical Society · 2024-03-14 · 13 citations

  articleOpen accessCorresponding

  Mosquito control methods are vital to curtail the spread of life-threatening illnesses, such as dengue fever, malaria, and yellow fever. Vector control technologies must be selective to minimize deleterious effects on our ecosystem. Successful methods that control mosquito larva populations utilize the uniquely high alkaline nature of the midgut. Here, we present novel protected triazabutadienes (pTBD) that are deprotected under basic conditions of the larval midgut, releasing an aryl diazonium ion (ADI) that results in protein modification. The probes contain a bioorthogonal terminal alkyne handle, enabling a selective Cu-click reaction with an azidofluorophore for quantification by SDS PAGE and visualization using fluorescence microscopy. A control TBD, unable to release an ADI, did not label the midgut. We envision our chemical probes will aid in the development of new selective mosquito control methods, thus preventing the spread of mosquito-borne illnesses with minimal impact on other organisms in the ecosystem.

  PublisherOA PDFDOI

• Chemical probes to interrogate the extreme environment of mosquito larval guts

  bioRxiv (Cold Spring Harbor Laboratory) · 2023-12-27

  preprintOpen access

  Mosquito control methods are vital for the spread of life-threatening illnesses such as dengue fever, malaria, and yellow fever. Vector control technologies must be selective to minimize deleterious effects to our ecosystem. Successful methods that control mosquito larva populations utilize the uniquely high alkaline nature of the midgut. Here, we present novel protected triazabutadienes (pTBD) which are deprotected under basic conditions of the larval midgut, releasing an aryl diazonium ion (ADI) that results in protein modification. The probes contain a bioorthogonal terminal alkyne handle, enabling a selective Cu-click reaction with an azido-fluorophore for quantification by SDS PAGE and visualization using fluorescence microscopy. A control TBD, unable to release an ADI, did not label the midgut. We envision our chemical probes will aid in the development of new selective mosquito control methods thus preventing the spread of mosquito-borne illnesses with minimal impact on other organisms in the ecosystem.

  PublisherOA PDFDOI

• Identification of Mosquito Eggshell Proteins from<i>Aedes aegypti</i>by Liquid Chromatography with Tandem Mass Spectrometry (LC–MS/MS) Proteomic Analysis

  Cold Spring Harbor Protocols · 2023-12-13 · 1 citations

  articleOpen access

  The insect eggshell is a multifunctional structure with several important roles, including generating an entry point for sperm via the micropyle before oviposition, serving as an oviposition substrate attachment surface, and functioning as a protective layer during embryo development. Eggshell proteins play major roles in eggshell tanning and hardening following oviposition and provide molecular cues that define dorsal–ventral axis formation. Precise eggshell formation during ovarian follicle maturation is critical for normal embryo development and the synthesis of a defective eggshell often gives rise to inviable embryos. Therefore, simple and accurate methods for identifying eggshell proteins will facilitate our understanding of the molecular pathways regulating eggshell formation and the mechanisms underlying normal embryo development. This protocol describes how to isolate and enrich eggshells from mature oocytes of Aedes aegypti mosquitoes and how to extract their eggshell proteins for liquid chromatography with tandem mass spectrometry (LC–MS/MS) proteomic analysis. Although this methodology was developed for studying mosquito eggshells, it may be applicable to eggs from a variety of insects. Mosquitoes are ideal model organisms for this study as their ovarian follicle development and eggshell formation are meticulously regulated by blood feeding and their follicles develop synchronously throughout oogenesis in a time-dependent manner.

  PublisherOA PDFDOI

• Differences in Longevity and Temperature-Driven Extrinsic Incubation Period Correlate with Varying Dengue Risk in the Arizona–Sonora Desert Region

  Viruses · 2023-03-26 · 5 citations

  articleOpen accessSenior author

  mosquitoes, dengue viruses, and humans. Emergence in new geographic areas can be unpredictable, with some regions having established mosquito populations for decades without locally acquired transmission. Key factors such as mosquito longevity, temperature-driven extrinsic incubation period (EIP), and vector-human contact can strongly influence the potential for disease transmission. To assess how these factors interact at the edge of the geographical range of dengue virus transmission, we conducted mosquito sampling in multiple urban areas located throughout the Arizona-Sonora desert region during the summer rainy seasons from 2013 to 2015. Mosquito population age structure, reflecting mosquito survivorship, was measured using a combination of parity analysis and relative gene expression of an age-related gene, SCP-1. Bloodmeal analysis was conducted on field collected blood-fed mosquitoes. Site-specific temperature was used to estimate the EIP, and this predicted EIP combined with mosquito age were combined to estimate the abundance of "potential" vectors (i.e., mosquitoes old enough to survive the EIP). Comparisons were made across cities by month and year. The dengue endemic cities Hermosillo and Ciudad Obregon, both in the state of Sonora, Mexico, had higher abundance of potential vectors than non-endemic Nogales, Sonora, Mexico. Interestingly, Tucson, Arizona consistently had a higher estimated abundance of potential vectors than dengue endemic regions of Sonora, Mexico. There were no observed city-level differences in species composition of blood meals. Combined, these data offer insights into the critical factors required for dengue transmission at the ecological edge of the mosquito's range. However, further research is needed to integrate an understanding of how social and additional environmental factors constrain and enhance dengue transmission in emerging regions.

  PublisherOA PDFDOI

• Mosquito Egg Development and Eggshell Formation

  Cold Spring Harbor Protocols · 2023-12-13 · 2 citations

  article

  Anautogenous female mosquitoes, which ingest a blood meal from warm-blooded vertebrates to produce eggs, have become a valuable model organism for investigating signaling pathways and physiological processes that occur during egg development. Different molecular pathways tightly regulate the initiation of egg development and are governed by a balance among different insect hormones. Gravid (mature egg-carrying) females deposit fully developed eggs at the end of each gonotrophic cycle, which is defined as the time interval between the ingestion of a blood meal to oviposition. An intact eggshell protects the oocyte and embryo inside from external factors such as desiccation, physical damage, etc., and the various eggshell proteins are spatially and temporary deposited during oogenesis. Additionally, follicle resorption (oosorption) during blood meal–induced mosquito ovarian follicle development is an adapted physiological process that optimizes reproductive fitness. Mosquito oocytes grow and mature synchronously throughout oogenesis; however, during the later stages of oogenesis, some oocytes may undergo oosorption if sufficient nutrients are unavailable. This introduction highlights how mosquito egg development can be used to investigate follicular resorption and identify proteins involved in eggshell formation in Aedes aegypti mosquitoes.

  PublisherDOI

Recent grants

• Improving Anopheline fitness and resistance through fat body insulin signaling

  NIH · $426k · 2016–2019

• NIH Grant R56AI107263

  NIH · $775k · 2016

• NIH Grant R01AI073745

  NIH · $2.5M · 2014

• NIH Grant R56AI118926

  NIH · $707k · 2018

• Midgut mitochondrial function as a driver of resistance and fitness in mosquitoes

  NIH · $726k · 2018–2021

Frequent coauthors

• Shirley Luckhart

  28 shared

• Nazzy Pakpour

  Novozymes (United States)

  15 shared

• Mark R. Brown

  University of Georgia

  11 shared

• Kacey C. Ernst

  University of Arizona

  11 shared

• Kathleen Walker

  University of Arizona

  10 shared

• Eileen Jeffrey Gutiérrez

  University of California, San Francisco

  8 shared

• Ming Tan

  China Medical University

  7 shared

• Robert M. Waterhouse

  SIB Swiss Institute of Bioinformatics

  7 shared

Labs

• The Riehle LabPI

  People currently working in the lab of Michael Riehle