Image courtesy Dr. Sadie Ryan

Speaker: Dr. Sadie Ryan

Associate Professor, Department of Geography, University of Florida

Thursday, January 16, 2020

2:50-3:50 PM (Period 8)

Turlington Hall Room 3018

University of Florida

All are welcome to attend.

Forecasting the impacts of climate change on vector-borne diseases (VBDs)—especially those under current public scrutiny and concern, such as malaria, dengue, chikungunya, and Zika—is a key component of global public health preparedness, and a key component of the ongoing issue of climate change preparedness. In this talk, I will showcase a strategy for applying ecophysiological models of temperature-dependent transmission to current and future climate models at large scales. I will demonstrate how our collaborative team have used these models to explore future scenarios for malaria, and for Aedes spp transmitted diseases, and how we can use mapping approaches as useful visualization tools, and how we tackle describing the multiple potential outcomes. I will also describe some local-scale, city and province level approaches to understanding vectorborne disease dynamics and management, and explore issues of how these two scales come together (or don’t) for decision making on the ground and in the boardroom.

Bio: Sadie J. Ryan is an Associate Professor of Medical Geography in the Department of Geography and in the Emerging Pathogens Institute (EPI) at the University of Florida, and PI of the Quantitative Disease Ecology and Conservation (QDEC) Lab group (

Ryan’s training is in Ecology and Evolutionary Biology (BA, Princeton), with an emphasis on conservation biology, quantitative ecology, and particularly, disease ecology. Ryan’s PhD work (UC Berkeley) centered on African buffalo spatial ecology in their savanna environment, in the context of an epidemic of Bovine Tuberculosis. Ryan’s postdoctoral work in Anthropological Science (Stanford, McGill), Ecology (NCEAS) and Geography (UCSB), launched her interdisciplinary work looking at the anthropogenic impacts of land use change, climate change, and conservation management goals in African parks landscapes, and the role of socioecological systems in disease transmission in Africa and Latin America.

This research continues today, investigating the multiscale issues of climate-health relationships in and on landscapes, and interactions with livelihoods, sustainability, parks management goals, the urban environment, and local perceptions. QDEC Lab is home to multiple projects in ecology at the human interface, spanning socioecological systems of vector borne and environmental disease ecology, climate-health modeling, insecticide resistance, and wildlife conservation, from Florida to the Old and New World tropics.


University of Florida Department of Geography
The Navi-Gator
January 2020, ISSUE 3 (Download PDF)

Evening of excellence

John & Fawn Dunkle Award for Graduate Student Travel: Ryan Good & Guoqian Yan
David L. Niddrie Excellence Fund: Tierney Shimansky & Shreejana Bhattarai
Little Family Student Fellowship Award: Caroline Parks
Ryan Poehling Award for Top Graduate Student: Michael Dillen (Top Master’s Student) & Cat Lippi (Top PhD Student)

Congratulations to our winners! We loved having you all for a night of celebration, reward and remembrance!

A Survey of Tick-Borne Bacterial Pathogens in Florida
Investigating diseases across mainland Florida!
A team from the University of Florida – including Geography’s Dr. Gregory Glass – has examined the distribution and presence of tick-bourne bacterial pathogens in Florida. Ticks were collected at 41 sites across Florida. DNA was extracted from 1,600 ticks – determining further investigation should be done to identify regional hotspots of tick-borne pathogens. Read more on the Geography website under “Recent Publications.”

12/5 Terry J. Doonan
Conserving Imperiled Mammal Species in Florida Across a Changing Landscape
Dr. Robert McCleery
Dr. Roberta Mendonça De Carvalho
Dr. Robert Walker
Where Are they now?
Our recent grads have found themselves in some interesting places!
Morgan Walker, class of 2019, works with Jason Blackburn as a Master’s research assistant.

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

RYANTemperature explains broad patterns of Ross River virus transmission

Marta Strecker Shocket, Sadie J Ryan, Erin A Mordecai

Article first published online: 28 AUG 2018 eLife

DOI: 10.7554/eLife.37762.001

ABSTRACT: Thermal biology predicts that vector-borne disease transmission peaks at intermediate temperatures and declines at high and low temperatures. However, thermal optima and limits remain unknown for most vector-borne pathogens. We built a mechanistic model for the thermal response of Ross River virus, an important mosquito-borne pathogen in Australia, Pacific Islands, and potentially at risk of emerging worldwide. Transmission peaks at moderate temperatures (26.4°C) and declines to zero at thermal limits (17.0 and 31.5°C). The model accurately predicts that transmission is year-round endemic in the tropics but seasonal in temperate areas, resulting in the nationwide seasonal peak in human cases. Climate warming will likely increase transmission in temperate areas (where most Australians live) but decrease transmission in tropical areas where mean temperatures are already near the thermal optimum. These results illustrate the importance of nonlinear models for inferring the role of temperature in disease dynamics and predicting responses to climate change.

Read the full publication at eLife.





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






Image courtesy of Proceedings of the Royal Society B. Months of transmission suitability in the Americas of dengue (left) and Zika (right).

GAINESVILLE, FL – A University of Florida Medical Geography researcher recently participated in a study that found that current estimates of Zika virus transmission vastly over predict its possible range. Temperature is a major driver of vector-borne disease transmission, but current transmission models rely on untested assumptions about life history of Zika infected Aedes aegypti mosquitoes. Previous models of Zika transmission were based on similarities between Zika and dengue fever.

The study, led by Dr. Courtney Murdock from the University of Georgia, examined the influence of temperature on Zika transmission in lab-reared Aedes mosquitoes at eight different constant temperatures. Zika transmits optimally at a temperature similar to dengue, but the lowest possible transmission temperature of Zika is 5 degrees centigrade warmer than dengue. As global average temperatures increase under climate change the range of Zika will expand north and into longer transmission seasons, but some areas that are currently suitable for Zika transmission will no longer support transmission.

UF Medical Geography professor Dr. Sadie Ryan used the temperature relationships to make updated models and maps, which she compared with previous transmission models. “These maps show that the predicted area for year round risk of Zika transmission is over 6 million square kilometers smaller than previous models would predict,” said Ryan. “This shows that Zika is not dengue and we need to have specific transmission models for specific diseases.”

The findings have been published in a paper titled Temperature drives Zika virus transmission: evidence from empirical and mathematical models in Proceedings of the Royal Society B.

The study was part of a collaboration between UF’s Dr. Sadie Ryan and Dr. Calistus Ngonghala, the CDC Southeastern Center of Excellence in Vector Borne Diseases, the University of Georgia, as well as investigators from Stanford University and Harvard Medical School.

Dr. Leah R. Johnson, Assistant Professor,
Department of Statistics, Virginia Tech

Mathematical models and the fundamental thermal niche of huanglongbing, a vector-borne pathogen of citrus trees

Speaker: Dr. Leah R. Johnson

Assistant Professor, Department of Statistics, Virginia Tech

Thursday, February 15, 2018

3:00-3:50 PM (Period 8)

Turlington Hall Room 3012

University of Florida

All are welcome to attend.

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.”


The world’s population will reach 8 billion by 2023.

One third of the world is TB positive; 300-500 million have malaria; more than 30 million live with HIV/AIDS.

Multi-drug resistance in urban settings, climate change, and disease-related mortality are going to impact your near future.