Age influences the thermal suitability of
            Plasmodium falciparum
            transmission in the Asian malaria vector
            Anopheles stephensi

Models predicting disease transmission are vital tools for long-term planning of malaria reduction efforts, particularly for mitigating impacts of climate change. We compared temperature-dependent malaria transmission models when mosquito life-history traits were estimated from a truncated portion of the lifespan (a common practice) versus traits measured across the full lifespan. We conducted an experiment on adult female Anopheles stephensi , the Asian urban malaria mosquito, to generate daily per capita values for mortality, egg production and biting rate at six constant temperatures. Both temperature and age significantly affected trait values. Further, we found quantitative and qualitative differences between temperature–trait relationships estimated from truncated data versus observed lifetime values. Incorporating these temperature–trait relationships into an expression governing the thermal suitability of transmission, relative R 0 ( T ), resulted in minor differences in the breadth of suitable temperatures for Plasmodium falciparum transmission between the two models constructed from only An. stephensi trait data. However, we found a substantial increase in thermal niche breadth compared with a previously published model consisting of trait data from multiple Anopheles mosquito species. Overall, this work highlights the importance of considering how mosquito trait values vary with mosquito age and mosquito species when generating temperature-based suitability predictions of transmission.

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Mosquito species and age influence thermal performance of traits relevant to malaria transmission

10.1101/769604 ◽

2019 ◽

Cited By ~ 2

Author(s):

KL Miazgowicz ◽

EA Mordecai ◽

SJ Ryan ◽

RJ Hall ◽

J Owen ◽

...

Keyword(s):

Disease Transmission ◽

Egg Production ◽

Life History Traits ◽

Anopheles Stephensi ◽

Mosquito Species ◽

Urban Malaria ◽

Temperature Dependent ◽

Biting Rate ◽

Transmission Models ◽

Target Intervention

AbstractModels predicting disease transmission are a vital tool in the control of mosquito populations and malaria reduction as they can target intervention efforts. We compared the performance of temperature-dependent transmission models when mosquito life history traits were allowed to change across the lifespan of Anopheles stephensi, the urban malaria mosquito, to models parameterized with commonly derived estimates of lifetime trait values. We conducted an experiment on adult female An. stephensi to generate daily per capita values for lifespan, egg production, and biting rate at six constant temperatures. Both temperature and age significantly affected trait values. Further, we found quantitative and qualitative differences between temperature-trait relationships estimated based on daily rates versus directly observed lifetime values. Incorporating these temperature-trait relationships into an expression governing transmission suitability, relative R0(T), model resulted in minor differences in the breadth of suitable temperatures for Plasmodium falciparum transmission between the two models constructed from only An. stephensi trait data, but a substantial increase in breadth compared to a previously published model consisting of trait data from multiple mosquito species. Overall this work highlights the importance of considering how mosquito trait values vary with mosquito age and mosquito species when generating temperature-based environmental suitability predictions of transmission.

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Exploring the lower thermal limits for transmission of human malaria, Plasmodium falciparum

10.1101/603787 ◽

2019 ◽

Author(s):

Jessica L. Waite ◽

Eunho Suh ◽

Penelope A. Lynch ◽

Matthew B. Thomas

Keyword(s):

Plasmodium Falciparum ◽

Anopheles Stephensi ◽

Parasite Development ◽

Temperature Dependent ◽

Single Degree ◽

Complete Development ◽

Thermal Limits ◽

Degree Day ◽

Extrinsic Incubation Period ◽

Impacts Of Climate Change

AbstractThe rate of malaria transmission is strongly determined by parasite development time in the mosquito, known as the extrinsic incubation period (EIP), since the quicker parasites develop, the greater the chance that the vector will survive long enough for the parasite to complete development and be transmitted. EIP is known to be temperature dependent but this relationship is surprisingly poorly characterized. There is a single degree-day model for EIP of Plasmodium falciparum that derives from a limited number of poorly controlled studies conducted almost a century ago. Here, we show that the established degree-day model greatly underestimates the rate of development of P. falciparum in both Anopheles stephensi and An. gambiae mosquitoes at temperatures in the range of 17-20°C. We also show that realistic daily temperature fluctuation further speeds parasite development. These novel results challenge one of the longest standing models in malaria biology and have potentially important implications for understanding the impacts of climate change.

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Satellite Imaging and Long-Term Mosquito Surveillance Implicate the Influence of Rapid Urbanization on Culex Vector Populations

Insects ◽

10.3390/insects10090269 ◽

2019 ◽

Vol 10 (9) ◽

pp. 269

Author(s):

Eleanor N. Field ◽

Ryan E. Tokarz ◽

Ryan C. Smith

Keyword(s):

Land Use ◽

Disease Transmission ◽

Culex Pipiens ◽

Management Practices ◽

Mosquito Species ◽

Land Use Changes ◽

Mosquito Vector ◽

Rapid Urbanization ◽

Mosquito Surveillance

The ecology and environmental conditions of a habitat have profound influences on mosquito population abundance. As a result, mosquito species vary in their associations with particular habitat types, yet long-term studies showing how mosquito populations shift in a changing ecological landscape are lacking. To better understand how land use changes influence mosquito populations, we examined mosquito surveillance data over a thirty-four-year period for two contrasting sites in central Iowa. One site displayed increasing levels of urbanization over time and a dramatic decline in Culex pipiens group (an informal grouping of Culex restuans, Culex pipiens, and Culex salinarius, referred to as CPG), the primary vectors of West Nile virus in central Iowa. Similar effects were also shown for other mosquito vector populations, yet the abundance of Aedes vexans remained constant during the study period. This is in contrast to a second site, which reflected an established urban landscape. At this location, there were no significant changes in land use and CPG populations remained constant. Climate data (temperature, total precipitation) were compiled for each location to see if these changes could account for altered population dynamics, but neither significantly influence CPG abundance at the respective site locations. Taken together, our data suggest that increased landscape development can have negative impacts on Culex vector populations, and we argue that long-term surveillance paired with satellite imagery analysis are useful methods for measuring the impacts of rapid human development on mosquito vector communities. As a result, we believe that land use changes can have important implications for mosquito management practices, population modeling, and disease transmission dynamics.

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Cryopreservation of Anopheles stephensi embryos

Scientific Reports ◽

10.1038/s41598-021-04113-x ◽

2022 ◽

Vol 12 (1) ◽

Author(s):

Eric R. James ◽

Yingda Wen ◽

James Overby ◽

Kristen Pluchino ◽

Shane McTighe ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Life Cycle ◽

Infectious Diseases ◽

Anopheles Stephensi ◽

Mass Storage ◽

Genetic Studies ◽

Transgenic Lines ◽

Cryopreservation Method ◽

Anopheline Mosquitoes

AbstractThe ability to cryopreserve mosquitoes would revolutionize work on these vectors of major human infectious diseases by conserving stocks, new isolates, lab-bred strains, and transgenic lines that currently require continuous life cycle maintenance. Efforts over several decades to develop a method for cryopreservation have, until now, been fruitless: we describe here a method for the cryopreservation of Anopheles stephensi embryos yielding hatch rates of ~ 25%, stable for > 5 years. Hatched larvae developed into fertile, fecund adults and blood-fed females, produced fully viable second generation eggs, that could be infected with Plasmodium falciparum at high intensities. The key components of the cryopreservation method are: embryos at 15–30 min post oviposition, two incubation steps in 100% deuterated methanol at − 7 °C and − 14.5 °C, and rapid cooling. Eggs are recovered by rapid warming with concomitant dilution of cryoprotectant. Eggs of genetically modified A. stephensi and of A. gambiae were also successfully cryopreserved. This enabling methodology will allow long-term conservation of mosquitoes as well as acceleration of genetic studies and facilitation of mass storage of anopheline mosquitoes for release programs.

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Periodic monitoring of vampire bats and rabies: a new framework for animal restoration projects in the Neotropics

10.32942/osf.io/53hda ◽

2020 ◽

Author(s):

Fernando Gonçalves ◽

Daniel G. Streicker ◽

Mauro Galetti

Keyword(s):

Disease Transmission ◽

Lessons Learned ◽

Multidisciplinary Teams ◽

Risk Area ◽

Food Web Structure ◽

Land Bridge ◽

High Risk Area ◽

Restoration Project ◽

Vampire Bats

Nowadays, restoration project might lead to increased public engagement and enthusiasm for biodiversity and is receiving increased media attention in major newspapers, TED talks and the scientific literature. However, empirical research on restoration project is rare, fragmented, and geographically biased and long-term studies that monitor indirect and unexpected effects are needed to support future management decisions especially in the Neotropical area. Changes in animal population dynamics and community composition following species (re)introduction may have unanticipated consequences for a variety of downstream ecosystem processes, including food web structure, predator-prey systems and infectious disease transmission. Recently, an unprecedented study in Brazil showed changes in vampire bat feeding following a rewilding project and further transformed the land-bridge island into a high-risk area for rabies transmission. Due the lessons learned from ongoing project, we present a novel approach on how to anticipate, monitor, and mitigate the vampire bats and rabies in rewilding projects. We pinpoint a series of precautions and the need for long-term monitoring of vampire bats and rabies responses to rewilding projects and highlighted the importance of multidisciplinary teams of scientist and managers focusing on prevention educational program of rabies risk transmitted by bats. In addition, monitoring the relative abundance of vampire bats, considering reproductive control by sterilization and oral vaccines that autonomously transfer among bats would reduce the probability, size and duration of rabies outbreaks. The rewilding assessment framework presented here responds to calls to better integrate the science and practice of rewilding and also could be used for long-term studying of bat-transmitted pathogen in the Neotropical area as the region is considered a geographic hotspots of “missing bat zoonoses”.

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Overexpression of Activated AMPK in the Anopheles stephensi Midgut Impacts Mosquito Metabolism, Reproduction and Plasmodium Resistance

Genes ◽

10.3390/genes12010119 ◽

2021 ◽

Vol 12 (1) ◽

pp. 119

Author(s):

Chioma Oringanje ◽

Lillian R. Delacruz ◽

Yunan Han ◽

Shirley Luckhart ◽

Michael A. Riehle

Keyword(s):

Egg Production ◽

Anopheles Stephensi ◽

Mitochondrial Dynamics ◽

Adult Life ◽

Blood Feeding ◽

Pathogen Resistance ◽

Α Subunit ◽

Significant Difference ◽

Transgenic Lines ◽

Ampk Activity

Mitochondrial integrity and homeostasis in the midgut are key factors controlling mosquito fitness and anti-pathogen resistance. Targeting genes that regulate mitochondrial dynamics represents a potential strategy for limiting mosquito-borne diseases. AMP-activated protein kinase (AMPK) is a key cellular energy sensor found in nearly all eukaryotic cells. When activated, AMPK inhibits anabolic pathways that consume ATP and activates catabolic processes that synthesize ATP. In this study, we overexpressed a truncated and constitutively active α-subunit of AMPK under the control of the midgut-specific carboxypeptidase promotor in the midgut of female Anopheles stephensi. As expected, AMPK overexpression in homozygous transgenic mosquitoes was associated with changes in nutrient storage and metabolism, decreasing glycogen levels at 24 h post-blood feeding when transgene expression was maximal, and concurrently increasing circulating trehalose at the same time point. When transgenic lines were challenged with Plasmodium falciparum, we observed a significant decrease in the prevalence and intensity of infection relative to wild type controls. Surprisingly, we did not observe a significant difference in the survival of adult mosquitoes fed either sugar only or both sugar and bloodmeals throughout adult life. This may be due to the limited period that the transgene was activated before homeostasis was restored. However, we did observe a significant decrease in egg production, suggesting that manipulation of AMPK activity in the mosquito midgut resulted in the re-allocation of resources away from egg production. In summary, this work identifies midgut AMPK activity as an important regulator of metabolism, reproduction, and innate immunity in An. stephensi, a highly invasive and important malaria vector species.

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An Efficient Alternative to the CDC Gravid Trap for Southern House Mosquito (Diptera: Culicidae) Surveillance

Journal of Medical Entomology ◽

10.1093/jme/tjaa259 ◽

2020 ◽

Author(s):

Timothy D McNamara ◽

Thomas A O’Shea-Wheller ◽

Nicholas DeLisi ◽

Emily Dugas ◽

Kevin A Caillouet ◽

...

Keyword(s):

United States ◽

Mosquito Species ◽

Red Light ◽

Light Trap ◽

The United States ◽

Light Traps ◽

Efficient Alternative ◽

Gravid Trap ◽

Trapping Trials

Abstract West Nile virus (WNV) is the most prevalent arbovirus found throughout the United States. Surveillance of surface breeding Culex vectors involved in WNV transmission is primarily conducted using CDC Gravid traps. However, anecdotal claims from mosquito abatement districts in Louisiana assert that other trap types may be more suited to WNV surveillance. To test the validity of these assertions, we conducted a series of trapping trials and WNV surveillance over 3 yr to compare the efficacy of multiple trap types. First, we compared the CDC Gravid trap, CO2-baited New Standard Miniature Blacklight traps, and CO2-baited CDC light traps with either an incandescent light, a red light, or no light. We found that the CDC Gravid trap and CO2-baited no-light CDC Light trap collected the most mosquitoes. Second, we conducted additional, long-term trapping and WNV surveillance to compare these two trap types. We found that CO2-baited no-light CDC traps collected more of the local WNV vector, Culex quinquefasciatus (Say, Diptera, Culicidae), and detected WNV with greater sensitivity. Finally, we conducted trapping to compare the physiological states of Cx. quinquefasciatus and diversity of collected mosquitoes. CO2-baited no-light CDC light traps collected more unfed Cx. quinquefasciatus while Gravid traps collected more blooded Cx. quinquefasciatus; both traps collected the same number of gravid Cx. quinquefasciatus. Additionally, we found that CO2-baited no-light CDC light traps collected a larger diversity of mosquito species than Gravid traps.

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Understanding mosquito host-choice behaviour: a new and low-cost method of identifying the sex of human hosts from mosquito blood meals

Parasites & Vectors ◽

10.1186/s13071-021-04577-w ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Fiona Teltscher ◽

Sophie Bouvaine ◽

Gabriella Gibson ◽

Paul Dyer ◽

Jennifer Guest ◽

...

Keyword(s):

Blood Meal ◽

Host Species ◽

Disease Transmission ◽

Low Cost ◽

Host Choice ◽

Epidemiological Models ◽

Choice Behaviour ◽

Vector Borne ◽

Transmission Models ◽

Blood Meals

Abstract Background Mosquito-borne diseases are a global health problem, causing hundreds of thousands of deaths per year. Pathogens are transmitted by mosquitoes feeding on the blood of an infected host and then feeding on a new host. Monitoring mosquito host-choice behaviour can help in many aspects of vector-borne disease control. Currently, it is possible to determine the host species and an individual human host from the blood meal of a mosquito by using genotyping to match the blood profile of local inhabitants. Epidemiological models generally assume that mosquito biting behaviour is random; however, numerous studies have shown that certain characteristics, e.g. genetic makeup and skin microbiota, make some individuals more attractive to mosquitoes than others. Analysing blood meals and illuminating host-choice behaviour will help re-evaluate and optimise disease transmission models. Methods We describe a new blood meal assay that identifies the sex of the person that a mosquito has bitten. The amelogenin locus (AMEL), a sex marker located on both X and Y chromosomes, was amplified by polymerase chain reaction in DNA extracted from blood-fed Aedes aegypti and Anopheles coluzzii. Results AMEL could be successfully amplified up to 24 h after a blood meal in 100% of An. coluzzii and 96.6% of Ae. aegypti, revealing the sex of humans that were fed on by individual mosquitoes. Conclusions The method described here, developed using mosquitoes fed on volunteers, can be applied to field-caught mosquitoes to determine the host species and the biological sex of human hosts on which they have blood fed. Two important vector species were tested successfully in our laboratory experiments, demonstrating the potential of this technique to improve epidemiological models of vector-borne diseases. This viable and low-cost approach has the capacity to improve our understanding of vector-borne disease transmission, specifically gender differences in exposure and attractiveness to mosquitoes. The data gathered from field studies using our method can be used to shape new transmission models and aid in the implementation of more effective and targeted vector control strategies by enabling a better understanding of the drivers of vector-host interactions.

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Behavioural response of mosquito vectors Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus to synthetic pyrethroid and organophosphorus-based slow-release insecticidal paint

Parasites & Vectors ◽

10.1186/s13071-021-04746-x ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Sunil Dhiman ◽

Kavita Yadav ◽

B. N. Acharya ◽

Raj Kumar Ahirwar ◽

D. Sukumaran

Keyword(s):

Aedes Aegypti ◽

Culex Quinquefasciatus ◽

Anopheles Stephensi ◽

Slow Release ◽

Disease Risk ◽

Mosquito Species ◽

Escape Time ◽

Behavioural Avoidance ◽

Vector Mosquito ◽

Contact Exposure

Abstract Background The direct toxicological impact of insecticides on vector mosquitoes has been well emphasized; however, behavioural responses such as excito-repellency and physical avoidance as a result of insecticide exposure have not been much studied. We have demonstrated the excito-repellency and behavioural avoidance in certain vector mosquito species on exposure to a slow-release insecticidal paint (SRIP) formulation in addition to direct toxicity. Methods A SRIP formulation developed by the Defence Research and Development Establishment, Gwalior, contains chlorpyriphos, deltamethrin and pyriproxyfen as active insecticides. Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti mosquitoes were used to study the excito-repellency response of the formulation. The experiments were performed in a specially designed dual-choice exposure and escape chamber made of transparent polymethyl methacrylate. For the experiments, the SRIP formulation was applied undiluted at a rate of 8 m2 per kg on 15 cm2 metallic surfaces. Mosquitoes were introduced into the exposure chamber, and observations of the movement of mosquitoes into the escape chamber through the exit portal were taken at 1-min intervals for up to 30 min. Results The evaluated formulation displayed strong excito-repellency against all three tested vector mosquito species. Results showed that the ET50 (escape time 50%) for Ae. aegypti, An. stephensi and Cx. quinquefasciatus was 20.9 min, 14.5 min and 17.9 min for contact exposure (CE) respectively. Altogether in CE, the escape rates were stronger in An. stephensi mosquitoes at different time intervals compared to Ae. aegypti and Cx. quinquefasciatus mosquitoes. The probit analysis revealed that the determined ET did not deviate from linearity for both non-contact exposure (NCE) and placebo exposure (PE) (χ2 ≤ 7.9; p = 1.0) for Ae. aegypti mosquitoes and for NCE (χ2 = 8.3; p = 1.0) and PE (χ2 = 1.7; p = 1.0) treatments in Cx. quinquefasciatus. Mortality (24 h) was found to be statistically higher (F = 6.4; p = 0.02) in An. stephensi for CE but did not vary for NCE (p ≥ 0.3) and PE (p = 0.6) treatments among the tested mosquito species. Survival probability response suggested that all the three tested species displayed similar survival responses for similar exposures (χ2 ≤ 2.3; p ≥ 0.1). Conclusion The study demonstrates the toxicity and strong behavioural avoidance in known vector mosquito species on exposure to an insecticide-based paint formulation. The combination of insecticides in the present formulation will broaden the overall impact spectrum for protecting users from mosquito bites. The efficacy data generated in the study provide crucial information on the effectiveness of the tested formulation and could be useful in reducing the transmission intensity and disease risk in endemic countries.

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Reducing Morbidity and Mortality Rates from COVID-19, Influenza and Pneumococcal Illness in Nursing Homes and Long-Term Care Facilities by Vaccination and Comprehensive Infection Control Interventions

Geriatrics ◽

10.3390/geriatrics6020048 ◽

2021 ◽

Vol 6 (2) ◽

pp. 48

Author(s):

Roger E. Thomas

Keyword(s):

Nursing Homes ◽

Infection Control ◽

Strong Evidence ◽

Disease Transmission ◽

Long Term Care ◽

Term Care ◽

Care Facilities ◽

Meta Analyses ◽

Tract Infections

The COVID-19 pandemic identifies the problems of preventing respiratory illnesses in seniors, especially frail multimorbidity seniors in nursing homes and Long-Term Care Facilities (LCTFs). Medline and Embase were searched for nursing homes, long-term care facilities, respiratory tract infections, disease transmission, infection control, mortality, systematic reviews and meta-analyses. For seniors, there is strong evidence to vaccinate against influenza, SARS-CoV-2 and pneumococcal disease, and evidence is awaited for effectiveness against COVID-19 variants and when to revaccinate. There is strong evidence to promptly introduce comprehensive infection control interventions in LCFTs: no admissions from inpatient wards with COVID-19 patients; quarantine and monitor new admissions in single-patient rooms; screen residents, staff and visitors daily for temperature and symptoms; and staff work in only one home. Depending on the vaccination situation and the current risk situation, visiting restrictions and meals in the residents’ own rooms may be necessary, and reduce crowding with individual patient rooms. Regional LTCF administrators should closely monitor and provide staff and PPE resources. The CDC COVID-19 tool measures 33 infection control indicators. Hand washing, social distancing, PPE (gowns, gloves, masks, eye protection), enhanced cleaning of rooms and high-touch surfaces need comprehensive implementation while awaiting more studies at low risk of bias. Individual ventilation with HEPA filters for all patient and common rooms and hallways is needed.

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