GAINESVILLE – In the battle against vector borne disease, mosquito control using insecticides is an essential tool. But what happens when that tool starts to fail, and how do you know it? Insecticides are regularly used by public health agencies to reduce populations of blood-sucking mosquitoes. Effective control programs are important to public health because, in addition to posing a nuisance, mosquitoes can also spread diseases to humans. Insecticide resistance, where mosquitoes adapt to survive exposure to commonly-used chemicals, has become an increasingly pressing issue for many health agencies, undermining mosquito control efforts. New research by the Quantitative Disease Ecology and Conservation (QDEC) Lab Group at the University of Florida, the Center for Research on Health in Latin America (CISeAL) at Pontificia Universidad Católica del Ecuador (PUCE), the Institute for Global Health and Translational Science at SUNY Upstate Medical University, Escuela Superior Politécnica del Litoral (ESPOL), and the Universidad Técnica de Machala is the first attempt to investigate seasonal and geographic variations of mosquito insecticide resistance in southern coastal Ecuador, a region where mosquito control is key to stopping the spread of serious diseases like Zika and dengue fever. The study was funded by the U.S. Centers for Disease Control and Prevention (CDC). The team of researchers used both genetic screening and pesticide assays to evaluate insecticide resistance in mosquitoes collected in urban locations at different seasons. Differences in the resistance status of mosquitoes to the insecticides commonly used by the local health ministry were found both across collection seasons and across the four cities in the study area. Detected resistance to Malathion, deltamethrin, and alpha-cypermethrin was particularly high in the port city of Machala, which has a long history of dengue outbreaks and insecticide use. Information on insecticide resistance status, patterns, and timing will help local public health professionals design sustainable mosquito control programs that will continue to be effective in the fight against disease.

Read Seasonal and geographic variation in insecticide resistance in Aedes aegypti in southern Ecuador, at PLoS Neglected Tropical Diseases.

La Resistencia a los Insecticidas Amenaza el Control de las Enfermedades Transmitidas por Mosquitos en Ecuador

GAINESVILLE – En la batalla contra las enfermedades transmitidas por vectores, el uso de insecticidas para el control de mosquito es una herramienta esencial. Pero ¿qué sucede cuando esa herramienta comienza a fallar y cómo lo sabe? Las agencias de salud pública utilizan regularmente los insecticidas para reducir las poblaciones de mosquitos que chupan la sangre. Los programas de control efectivos son importantes para la salud pública porque, además de ser una molestia, los mosquitos también pueden transmitir enfermedades a los humanos. La resistencia hacia los insecticidas, donde los mosquitos se adaptan para sobrevivir a la exposición a sustancias químicas de uso común, se ha convertido en un problema cada vez más urgente para muchas agencias de salud, desfavoreciendo los esfuerzos de control de mosquitos. Una nueva investigación realizada por el Grupo de Laboratorios de Ecología y Conservación de Enfermedades Cuantitativas (QDEC) en la Universidad de Florida, el Centro de Investigación para la Salud en América Latina (CISeAL) en la Pontificia Universidad Católica del Ecuador (PUCE), el Instituto de Salud Global y la Ciencia Traslacional en la Universidad Médica del Estado de SUNY, la Escuela Superior Politécnica del Litoral (ESPOL), y la Universidad Técnica de Machala es el primer intento en investigar las variaciones estacionales y geográficas sobre resistencia a insecticidas en mosquitos en la costa sur de Ecuador, una región donde el control de mosquitos es clave para detener la propagación de enfermedades graves como el Zika y el Dengue. El estudio fue financiado por los Centros para el Control y la Prevención de Enfermedades (CCPEEU). El equipo de investigación usó tanto análisis genético como los ensayos de pesticidas para evaluar la resistencia a insecticidas en los mosquitos recolectados en áreas urbanas, en diferentes estaciones. Diferencias en el estado de resistencia en mosquitos a los insecticidas comúnmente utilizados por el ministerio de salud local, se encontraron tanto en las diferentes temporadas de recolección, como en las cuatro ciudades dentro del área de estudio. La resistencia detectada al malatión, la deltametrina, y la alfa-cipermetrina fue particularmente alta en la ciudad portuaria de Machala, que tiene una larga historia de brotes de dengue y uso de insecticidas. La información sobre el estado de resistencia hacia insecticidas, los patrones y el tiempo ayudará a los profesionales de la salud pública local a diseñar programas sostenibles de control de mosquitos que continuarán siendo eficaces en la lucha contra la enfermedad.

Lee Seasonal and geographic variation in insecticide resistance in Aedes aegypti in southern Ecuador, en PLoS Neglected Tropical Diseases.

 

Media contact: Mike Ryan Simonovich

Image credit: CDC/ Prof. Frank Hadley Collins, Dir., Cntr. for Global Health and Infectious Diseases, Univ. of Notre Dame/James Gathany

GAINESVILLE – Blood sucking insects such as the Yellow fever mosquito, Aedes aegypti, are more than just a nuisance in Ecuador, they also spread diseases such as dengue fever, chikungunya and Zika. A warming world means that public health officials must decide where to direct surveillance and mosquito control efforts not only today, but also decades down the road given dramatic shifts in mosquito habitat that will take place thanks to climate change.

Ecuadorian agencies now have a powerful helping hand: a recent paper in PLoS Neglected Tropical Diseases provides detailed maps forecasting where mosquitoes – and diseases – are likely to be in a warmer future.

The new work from the University of Florida’s Quantitative Disease Ecology & Conservation Lab Group (QDEC Lab) and the Emerging Pathogens Institute assesses the current and future geographic distribution of Ae. aegypti throughout Ecuador. The study was led by PhD Candidate Ms. Cat Lippi and is the result of a long-term collaboration with SUNY Upstate Medical University and the Ecuadorian Ministry of Health. Lippi’s committee chair, EPI researcher and QDEC founder Dr. Sadie Ryan, also contributed to the project, as did EPI investigator Dr. Jason Blackburn.

The research team repurposed historic larval mosquito surveillance data collected by the Ministry of Health between 2000 and 2012 in Ecuadorian households to predict where Ae. aegypti may occur in areas that have not yet been surveyed. Aedes aegypti mosquitoes are important because they are a vector for several different mosquito-borne diseases and are able to reproduce in small quantities of standing water, making them common in urban settings. The research team used environmental and climate modeling to analyze how areas currently suitable for the mosquito may shift in the future as a result of climate change.

Maps A and E show mosquito distribution today while maps B-D and F-H show where mosquitoes can be predicted in the future given different climate change scenarios.

“We wanted to show the Ministry of Health in Ecuador where disease-carrying mosquitoes might occur in the future,” Lippi says. By analyzing the environmental and climactic characteristics associated with where mosquitoes occur in Ecuador today, the team extrapolated where mosquitoes may occur in 2050 under a range of climate change scenarios and used the presence of these mosquitoes as a proxy for where disease would occur.

The models show that Ae. aegypti are likely to expand their range into regions of transitional elevation along the Andes mountain range by midcentury. The expanded habitat includes the portion of mountainous area where valley floors give way to a mountain’s lower slopes. The higher reaches of the Andes famed peaks are expected to remain protected pockets that will still be too cool, even with extreme warming, for Ae. aegypti to survive. At the same time, changing climate will reduce the mosquito’s range in the eastern portion of the country’s Amazon.

“When there is a population that has never been exposed to pathogens like dengue or Zika, they don’t have any immunity, and that population will be vastly more susceptible to an acute outbreak,” Lippi says. “There are thousands of Ecuadorians who will be exposed to mosquitoes in the future who have never had to deal with them before.”

The team will share their results with the Ecuadorian Ministry of Health, which will use the data to prepare for the future. Previous work through the team’s collaboration with Ecuador’s Ministry of Health showed that local knowledge and attitudes are significantly associated with the risk of Ae. aegypti mosquitoes in households in Ecuador, although effects on actual dengue fever risk are less clear. Mosquito-borne diseases pose a serious threat to public health throughout Ecuador and Latin America, where dengue alone accounts for an estimated 16 million infections occurring in the Americas each year.

“Our work gives their health department good forewarning of where to focus their preparations to prevent future outbreaks, and this will help them to conserve limited resources,” Lippi says. Preparations may include educational campaigns on using insect repellent, and window and door screens, as well as how to safely store household water in covered containers. The government can also coordinate spraying efforts to reduce mosquito larvae in the environment.

“Of course we expect to see changes in habitat and species’ ranges due to future climate change,” Lippi says. “But what this study addresses is the question of where those changes will occur, and how severe those changes may be, all within the context of disease risk to people.”

Un nuevo estudio de la Universidad de Florida (Estados Unidos) sugiere que los mosquitos que transmiten enfermedades podrían infectar a poblaciones humanas en Los Andes ecuatorianos debido al cambio climático

Comunidades en Latino América tienen el desafío de reducir la exposición a mosquitos que transmiten enfermedades, como el Aedes aegypti. En Ecuador, este mosquito es más que una molestia. El Aedes aegypti trasmite víruses que causan enfermedades de alta consideración para la salud pública incluyendo dengue, chikungunya y Zika. Dónde el Ministerio de Salud Publica (MSP) podría enfocar los esfuerzos de vigilancia y control de estos mosquitos, hoy y en el futuro, tomando en cuenta el cambio climático?

Un nuevo estudio del grupo, Ecología de Enfermedades y Conservación Cuantitativa (QDEC), de la Universidad de Florida, analiza la distribución geográfica del Aedes aegypti a través de todo Ecuador. El proyecto fue dirigido por Cat Lippi, estudiante de PhD de QDEC, y es el resultado de una colaboración a largo plazo con la Universidad del Estado de New York y Universidad Médica de “Upstate” (SUNY UPSTATE) y el MSP del Ecuador. El equipo de investigadores usó datos históricos de vigilancia de mosquitos recolectados por el MSP para predecir lugares donde Aedes aegypti podría estar presente. Áreas que no se ha inspeccionado de una manera activa y áreas donde podría estar presente en el futuro bajo condiciones de cambio climático. Modelos de “nicho ecológico” fueron creados usando información sobre lugares con la presencia actual del moquito y con variables básicos del ambiente. Los modelos fueron desarrollados usando condiciones climatológicas actuales y futuras, hasta el año 2050.

Este estudio muestra que lugares con elevaciones intermedias a lo largo de Los Andes pueden convertirse en zonas mas asequibles para la presencia de Aedes aegypti en el año 2050. Este descubrimiento sugiere que la población que actualmente viven en estas zonas de transición puede correr el riesgo, en el futuro, de ser expuesto a enfermedades transmitidas por mosquitos, como resultado de cambio climático. Los autores reportan que aumentará la población con riesgo de exposición por más de 12,000 personas bajo los escenarios extremos de cambio climático. Al mismo tiempo, los investigadores identificaron áreas que pueden ser menos propicias para los mosquitos, como la cuenca de la Amazonia.

Actualmente, la mayor parte de las personas que viven en Los Andes están protegidos por las enfermedades transmitidos por mosquitos debido a las altas elevaciones, lo que produce un ambiente frio y no apto para los moquitos. En situaciones extremas de cambio climático, los mosquitos pueden invadir nuevas lugares con elevación de 900 metros más alto que los lugares en actuales condiciones climatológicas. “Las personas que vivan en esta zona de expansión de enfermedades pueden ser más susceptibles a futuros brotes de enfermedades debido a varios factores, incluyendo falta de inmunidad debido a exposición previa al patógeno y falta de conocimiento y costumbres asociados con la prevención de mosquitos y costumbres de protección personal, como el uso de repelente,” indica Lippi. Estudios previos en colaboración con el MSP del Ecuador mostraron que el conocimiento y actitudes de las poblaciones locales están asociados con el riesgo de la presencia de Aedes aegypti en hogares en Machala. Se recomienda estudios en estos nuevas áreas de futuro riesgo.

Las enfermedades transmitidas por mosquitos son una amenaza para la salud pública en toda Latinoamérica, donde dengue causa aproximadamente 16 millones de infecciones anualmente. Estudios como éstos enfatizan la importancia de incorporar la ciencia de “Geografía de la salud” dentro de los estándares de la práctica de la educación pública, proveyendo información más precisa a las agencias de salud pública para mejorar el uso de escasos recursos para el de control de estas enfermedades y para desarrollar intervenciones de control vectorial y de educación pública en lugares específicos.

Media contact: Mike Ryan Simonovich

GAINESVILLE, FL – With its turquoise waters and abundant wildlife, Ecuador’s Galapagos Islands have long been a vacation dream of many. Tourist guides highlight playful sea lions and giant tortoises, but they do not talk about the mosquitoes. For the more than 30,000 people who live there, emerging epidemics of mosquito-borne disease such as dengue, Zika, and chikungunya, which causes fever and joint pain, are an ongoing threat.

A new Medical Geography study led by UF medical geographer Dr. Sadie J. Ryan, examined the social ecological factors associated with dengue fever and mosquito presence in the Galapagos Islands. This work by UF Geography’s Quantitative Disease Ecology & Conservation Lab Group, is the first of its kind conducted in the Galapagos, where dengue has been considered a newly emerging disease since cases were first detected in the early 2000’s.

Ryan collaborated with the Biosecurity Agency of the Galapagos and colleagues from the Universidad San Francisco de Quito, the Escuela Superior Politecnica del Litoral, and SUNY Upstate Medical University as well as UF Geography PhD Student Catherine Lippi and Postdoctoral Fellow Dr. Gabriella Hamerlinck. The team conducted household questionnaires and entomological surveys on the two most populated islands — Santa Cruz and San Cristobal. Statistical models were developed to identify the risk factors for the presence of self-reported dengue infection and Aedes aegypti, an invasive mosquito species that transmits dengue and other viral diseases.

Dengue fever is a serious disease throughout Ecuador and Latin America, with an estimated 16 million cases occurring in the Americas annually. Ryan emphasized, “The Galapagos Islands, and other island systems, present a unique challenge for vector control, given the difficulty in surveying and controlling mosquitoes across diverse landscapes separated by the ocean.”

Researchers found that the knowledge and attitudes of study participants were significantly associated with disease risk. They learned that water storage contributes to risk among island residents, but covering those containers reduces it. Because fresh water is scarce, the islands’ inhabitants store water in containers that attract mosquitoes that settle there. The study also found that human movement played an important role in dengue transmission, as people traveling between islands and traveling to the mainland may be exposed to the dengue virus and bring the disease back to their local communities.

“Our findings suggest that public health officials could develop targeted interventions that increase people’s knowledge of dengue transmission while changing their behaviors to prevent exposure to mosquito bites”, says Ryan.

This study has important implications for the formation of new health policies, providing localized information that will help reduce future outbreaks. Senior author, Anna Stewart-Ibarra of Upstate Medical University, says, “We need more research dedicated to understanding the health and well being of tens of thousands of local residents and hundreds of thousands of tourists who visit the Galápagos Islands each year, and how these health outcomes interact with the unique local ecosystems and wildlife populations.”

This is the first study of its kind in the Galapagos, and the first time household level risks of dengue have been rigorously explored off the mainland of Ecuador.

The study was published in the International Journal of Environmental and Public Health in a special issue on mosquito-borne diseases.

 

 

 

 

 

 

 

RYANTemperature drives Zika virus transmission: evidence from empirical and mathematical models

Blanka Tesla, Leah R. Demakovsky, Erin A. Mordecai, Sadie J. Ryan, Matthew H. Bonds, Calistus N. Ngonghala, Melinda A. Brindley, Courtney C. Murdock

Article first published online: 15 AUG 2018 Proceedings of the Royal Society B

DOI: 10.1098/rspb.2018.0795

ABSTRACT: Temperature is a strong driver of vector-borne disease transmission. Yet, for emerging arboviruses we lack fundamental knowledge on the relationship between transmission and temperature. Current models rely on the untested assumption that Zika virus responds similarly to dengue virus, potentially limiting our ability to accurately predict the spread of Zika. We conducted experiments to estimate the thermal performance of Zika virus (ZIKV) in field-derived Aedes aegypti across eight constant temperatures. We observed strong, unimodal effects of temperature on vector competence, extrinsic incubation period and mosquito survival. We used thermal responses of these traits to update an existing temperature-dependent model to infer temperature effects on ZIKV transmission. ZIKV transmission was optimized at 29°C, and had a thermal range of 22.7°C–34.7°C. Thus, as temperatures move towards the predicted thermal optimum (29°C) owing to climate change, urbanization or seasonality, Zika could expand north and into longer seasons. By contrast, areas that are near the thermal optimum were predicted to experience a decrease in overall environmental suitability. We also demonstrate that the predicted thermal minimum for Zika transmission is 5°C warmer than that of dengue, and current global estimates on the environmental suitability for Zika are greatly over-predicting its possible range.

Read the full publication at Proceedings of the Royal Society B

 

 

 

 

 

Image courtesy Dr. Sadie Ryan
Image courtesy Dr. Sadie Ryan

GAINESVILLE, Fla. – A larger portion of Africa is currently at high risk for malaria transmission than previously predicted, according to a new University of Florida mapping study.

Under future climate regimes, the area where the disease can be transmitted most easily will shrink, but the total transmission zone will expand and move into new territory, according to the study, which appears in the current issue of the journal Vector-Borne and Zoonotic Diseases.

By 2080, the study shows, the year-round, highest-risk transmission zone will move from coastal West Africa, east to the Albertine Rift, between the Democratic Republic of Congo and Uganda. The area suitable for seasonal, lower-risk transmission will shift north into coastal sub-Saharan Africa.

Most striking, some parts of Africa will become too hot for malaria.

The overall expansion of malaria-vulnerable areas will challenge management of the deadly disease, said lead author Sadie Ryan, an assistant professor of geography at the University of Florida who also is affiliated with UF’s Emerging Pathogens Institute.

Malaria will arrive in new areas, posing a risk to new populations, she said, and the shift of endemic and epidemic areas will require public health management changes.

“Mapping a mathematical predictive model of a climate-driven infectious disease like malaria allows us to develop tools to understand both spatial and seasonal dynamics, and to anticipate the future changes to those dynamics,” Ryan said.

Cerebral malaria, caused by the parasite Plasmodium falciparum transmitted by the Anopheles gambiae mosquito, is the most deadly form of the disease, killing around 584,000 people each year. Malaria can cause organ failure, unconsciousness, and coma, if left untreated, and is a major cause of decreased economic productivity in affected regions.

The study uses a model that takes into account the real, curved, physiological responses of both mosquitoes and the malaria parasite to temperature. This model shows an optimal transmission temperature for malaria that, at 25 degrees Celsius, is 6 degrees Celsius lower than previous predictive models.

This work will play an important role in helping public health officials and NGOs plan for the efficient deployment of resources and interventions to control future outbreaks of malaria and their associated societal costs, Ryan said.

The collaborative research team includes experts in epidemiology, public health, ecology, entomology, mathematical modeling and geography. In addition to Ryan, other team members are Amy McNally (NASA), Leah Johnson (University of South Florida), Erin A. Mordecai (Stanford University), Tal Ben-Horin (Rutgers), Krijn Paaijmans (Universitat de Barcelona) and Kevin D. Lafferty (University of California, Santa Barbara).

The work expands upon the team’s prior work at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara.

RYAN – Mapping Physiological Suitability Limits for Malaria in Africa Under Climate Change

Ryan Sadie J., McNally Amy, Johnson Leah R., Mordecai Erin A., Ben-Horin Tal, Paaijmans Krijn, and Lafferty Kevin

Article first published online: 18 Nov 2015 Vector-Borne and Zoonotic Diseases

DOI: 10.1089/vbz.2015.1822

ABSTRACT: We mapped current and future temperature suitability for malaria transmission in Africa using a published model that incorporates nonlinear physiological responses to temperature of the mosquito vector Anopheles gambiae and the malaria parasite Plasmodium falciparum. We found that a larger area of Africa currently experiences the ideal temperature for transmission than previously supposed. Under future climate projections, we predicted a modest increase in the overall area suitable for malaria transmission, but a net decrease in the most suitable area. Combined with human population density projections, our maps suggest that areas with temperatures suitable for year-round, highest-risk transmission will shift from coastal West Africa to the Albertine Rift between the Democratic Republic of Congo and Uganda, whereas areas with seasonal transmission suitability will shift toward sub-Saharan coastal areas. Mapping temperature suitability places important bounds on malaria transmissibility and, along with local level demographic, socioeconomic, and ecological factors, can indicate where resources may be best spent on malaria control.

Read the full publication at Vector-Borne and Zoonotic Diseases 

GAINESVILLE, Florida — A new 5 year multi-institutional collaborative research grant of $1.85 million funded by the National Science Foundation’s Ecology and Evolution of Infectious Diseases (NSF EEID) program will support research on the effect of temperature on 13 different diseases transmitted by insects. It will also measure the capacity for two common disease-carrying mosquitoes in the Americas to adapt to new (or changing) temperatures.

Many of the world’s most devastating and neglected infectious diseases are spread to people by mosquitoes and other insects. Malaria, a mosquito-transmitted parasite, kills over 650,000 people each year. Dengue fever, an incurable mosquito-borne virus, infects around 400 million people annually, a rate which has grown dramatically in recent decades. With limited options for medical treatment or vaccination, preventing infection is the best way to control these diseases. This approach requires understanding—and predicting—how the climate affects mosquitoes and the diseases they carry.

“If we want to predict the spread of mosquito-transmitted diseases, we have to learn how these insects and pathogens respond to the environment and changing climate,” says Dr. Sadie Ryan, Assistant Professor of Medical Geography at the University of Florida and co-principal investigator on the project. “We will improve on our existing predictive models by validating them with real data. Integrating field data on local conditions with mapped model predictions will enable us to understand the multiscalar dynamics of climate-disease relationships”

Dr. Ryan (UF) and Dr. Anna Stewart Ibarra, Assistant Professor of Medicine at SUNY-Upstate Medical University will launch a new field project component in Ecuador. They will be adding new sites to their previous collaborative research on climate-dengue dynamics, starting the first of five years supported under this grant, with the onset of the coming dengue season.

“This is a critical component of the research,” says Dr. Stewart Ibarra, leader of the Ecuador field team. “Testing new and existing models on the ground in dengue-endemic areas will be a big step towards improving the science behind vector control and public health.”

The collaborative research team includes experts in epidemiology, public health, ecology, entomology, mathematical modeling, and geography: co-principal investigator Sadie Ryan (University of Florida), lead investigator Erin Mordecai (Stanford University), Anna Stewart Ibarra (SUNY Upstate Medical University), Matt Thomas (Penn State University), Leah Johnson and Jason Rohr (University of South Florida), Van Savage (UCLA), Marco Neira (Pontificia Universidad Católica del Ecuador (PUCE)), and other collaborators in Ecuador. The work expands upon Dr. Ryan’s prior work at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara and the Center for Global Health & Translational Science at SUNY-Upstate Medical University.

The team will begin work this year to develop temperature-sensitive transmission models and fit them with data from published sources for 13 vector-borne diseases: vivax malaria, trypanosomiasis, dengue, chikungunya, yellow fever, West Nile, Eastern equine encephalitis, Western equine encephalitis, St. Louis encephalitis, Rift Valley fever, Ockelbo (Sindbis) disease, Ross River fever, and bluetongue. By studying this suite of diseases, the team hopes to uncover general patterns of temperature responses across multiple insects and pathogens.

See the press release for more information on the newly funded projects in the Ecology and Evolution of Infectious Diseases Program, a joint program of the U.S. National Science Foundation, U.S. National Institutes of Health, U.S. Department of Agriculture, and U.K. Biotechnology and Biological Sciences Research Council.