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

MS. Stephanie Mundis (center) receives 2018 SEDAAG Best PhD Paper award

Second-year PhD student Stephanie Mundis of the Quantitative Disease Ecology & Conservation Lab, advised by Dr. Sadie Ryan, was recognized for her paper and presentation at the 2018 SouthEastern Division of the American Association of Geographers. Her presentation, “Spatial analysis of pyrethroid resistance genotypes in Aedes aegypti mosquitoes in Florida,” focused on spatial patterns in the genetic determinants of resistance in Aedes aegypti, a vector species that transmits dengue, chikungunya, and Zika viruses.

GAINESVILLE, FL – New model that accurately predicts patterns of mosquito-borne Ross River virus epidemics could help prepare for the impact of climate change.

Scientists have built a model that predicts how temperature affects the spread of Ross River virus, a common mosquito-borne virus in Australia, according to a report in the journal eLife.

The research demonstrates the importance of using temperature to predict epidemics of mosquito-borne diseases and could help public health bodies prepare for the impact of climate change on the spread of tropical diseases worldwide.

“Scientists are realising that warmer temperatures mean longer mosquito seasons and mosquitoes entering new regions where it was previously too cold for them to survive,” says senior author Erin Mordecai, Assistant Professor in Biology at Stanford University’s School of Humanities and Sciences. “Warm temperatures also speed up the biological processes that help mosquitoes spread viruses. But working out the precise effect of temperature on different stages of mosquito growth and spread of viruses is tricky, because so many factors are involved.”

Australia and the Ross River virus (RRV) offer an ideal opportunity to study the effects of temperature on disease transmission. RRV infects between 2,000–9,000 people each year in Australia and causes long-term joint pain and disability. Most people live in cities ranging in latitude from the north to the south of the country. Each season, as the temperature rises, RRV epidemics move from the subtropical north to temperate south.

The team used two species of mosquito most responsible for RRV outbreaks in Australia to build a model using laboratory data on traits such as mosquito growth, survival, bite rate and infectiousness in response to different temperatures. “Our model correctly predicted that RRV is endemic across tropical Northern Australia year-round, and is seasonally epidemic in the cooler regions of Southern Australia,” explains Sadie Ryan, Associate Professor of Medical Geography at the University of Florida, and second author of the study. “When human population data was added into the model, its prediction of seasonal patterns matched recorded human cases of RRV.”

The model determined that the optimal temperature for RRV spread was 26°C (80°F) and transmission would be limited at temperatures below 17°C (63°F) and above 32°C (89°F), which matches current patterns of disease. Mosquito lifespan was the most important temperature-dependent factor limiting transmission, and fertility and survival were prohibiting factors at temperatures that were too low or high for transmission. As transmission is limited by temperatures that are too cold and too hot, it may increase in some locations as a result of climate warming, while decreasing in others.

Our study provides strong evidence that temperature drives infection patterns at the continent-wide and seasonal levels,” says first author Marta Shocket, Postdoctoral Scientist in Stanford’s Biology Department. “In the short term, our work will help researchers build better statistical models for RRV which can be used to make more specific predictions based on climate change. In the long term, it should help mosquito control agencies better plan for the future and may provide further evidence of the need to combat climate change.”

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

 

 

 

 

 

Dr. Gregory Glass and Dr. Sadie Ryan

GAINESVILLE – With a $10 million grant from the Centers for Disease Control and Prevention, the University of Florida will lead a highly collaborative research program focused on stopping vector-borne diseases such as Zika before they spread farther into the United States.

Key leadership for the Southeast Regional Center of Excellence in Vector-Borne Disease will be provided by Medical Geographers Dr. Gregory Glass – Co-Principal Investigator for Ecological and Insecticide-resistance Models of Tick Vectors in Florida – and Dr. Sadie Ryan – Core Lead and Co-Investigator for Data Management, Biostatistics, and Communications (DMBC). The Center of Excellence (CoE) will be housed at UF’s Emerging Pathogens Institute (EPI), and will be a collaboration between the University of Florida, the University of Miami, Florida International University and the University of South Florida to share research to address the statewide and regional challenge of Zika and other diseases.

“This is a novel approach that integrates laboratory and field studies through intensive modeling of pathogens and their vectors,” Glass said. An important contribution from UF is in mathematical modeling, to quantify how well the field and lab based research solutions work.  “This is a massive collaborative effort, leveraging vector-borne disease expertise, data, and modeling, across multiple institutions and partners, to address the urgent needs of VBD management, particularly in the face of Zika”, said Ryan.

The grant is part of nearly $184 million in funding from the CDC to states, territories, local jurisdictions, and universities to support efforts to protect Americans from Zika virus infection and associated adverse health outcomes, including microcephaly and other serious birth defects. These awards are part of the $350 million in funding provided to CDC under the Zika Response and Preparedness Appropriations Act of 2016.

“Zika continues to be a threat to pregnant women,” said CDC Director Dr. Tom Frieden. “States, territories, and communities need this CDC funding to fight Zika and protect the next generation of Americans.”

Anopheles gambiae(https://www.flickr.com/photos/afpmb/13998232505/in/photolist-9y3cgk-adeXVQ-njGj7X-njYAQi-njYAJr-nZpKER-bBzyvE-cqfYAC-nvLzYy-5MXsA2-ngmLMV-ne4Pq9-nf7NJB-nekgUw-nwiejV-nvzhNr-nxBvR3-nqK2ca-nwgNPA-nekR1F-notrEJ-nvXJ3Q-notjXW-nwfsCV-nvh9Gh-nvBMnW-nvzcwz-nEEZLa-nxSeGF-nvZMaV-nf7qbG-nCSV1w-nwmuoh-nMvth3-nvENQN-nKpE9u-nf3Wnk-nMout3-nycSTV-nueT5Q-nCSjLj-norvnA-noqqBW-nEW7z4-ne5WzM-nopB9P-nGAgCa-ngndLa-9RQrLJ), AFPMB (https://www.flickr.com/photos/afpmb/), (CC BY-NC-ND 2.0)
Anopheles gambiae, AFPMB, (CC BY-NC-ND 2.0)

GAINESVILLE, Florida –A new study out of the University of Florida calls for caution in estimating the impact of mosquito control on malaria and other vector-borne disease transmission. Public health officials make prevention and treatment decisions based on models of the impact of interventions. For vector-borne diseases like malaria, these models are based on mosquito lifespan and the changing transmissibility of disease, as they age. The assumptions are often based on laboratory studies, which do not necessarily represent life in the wild – but how bad is that?

The study, published in the Ecological Society of America’s journal Ecosphere, explores how current models of the life history of Anopheles mosquitoes, the most important vector of malaria in sub-Saharan Africa, don’t always track with real world observations of mosquito mortality. The current models overestimate the average lifespan of Anopheles, and do not account for the shape of mortality in older individuals. These assumptions can lead to inflated estimates of malaria transmissibility.

The primary means of reducing malaria transmission entails preventing infected mosquitoes from biting people. This is currently accomplished by intervention strategies like spraying for mosquitoes, and sleeping under bednets.

“I think the key message is don’t overestimate the impact of the intervention by using the wrong mortality assumption; it’s bad business for public health.”, says the study’s lead author, Dr. Sadie Ryan, Assistant Professor of Medical Geography at the University of Florida. “If we want to prevent the spread of mosquito-transmitted diseases, public health officials need appropriate predictive models validated with real data.”

The collaborative research team includes experts in epidemiology, public health, ecology, entomology, mathematical modeling, and geography: lead author Sadie Ryan (University of Florida), co-author Tal Ben-Horin (Rutgers), and co-author Leah Johnson (University of South Florida). 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.