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.

 

 

 

 

 

 

 

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.

LIPPI, RYANNonlinear and delayed impacts of climate on dengue risk in Barbados: A modelling study

Rachel Lowe, Antonio Gasparrini, Cédric J. Van Meerbeeck, Catherine A. Lippi, Roché Mahon, Adrian R. Trotman, Leslie Rollock, Avery Q. J. Hinds, Sadie J. Ryan, Anna M. Stewart-Ibarra

Article first published online: 17 JUL 2018 PLOS Medicine

DOI: 10.1371/journal.pmed.1002613

ABSTRACT:

Background
Over the last 5 years (2013–2017), the Caribbean region has faced an unprecedented crisis of co-occurring epidemics of febrile illness due to arboviruses transmitted by the Aedes sp. mosquito (dengue, chikungunya, and Zika). Since 2013, the Caribbean island of Barbados has experienced 3 dengue outbreaks, 1 chikungunya outbreak, and 1 Zika fever outbreak. Prior studies have demonstrated that climate variability influences arbovirus transmission and vector population dynamics in the region, indicating the potential to develop public health interventions using climate information. The aim of this study is to quantify the nonlinear and delayed effects of climate indicators, such as drought and extreme rainfall, on dengue risk in Barbados from 1999 to 2016.

Methods and findings
Distributed lag nonlinear models (DLNMs) coupled with a hierarchal mixed-model framework were used to understand the exposure–lag–response association between dengue relative risk and key climate indicators, including the standardised precipitation index (SPI) and minimum temperature (Tmin). The model parameters were estimated in a Bayesian framework to produce probabilistic predictions of exceeding an island-specific outbreak threshold. The ability of the model to successfully detect outbreaks was assessed and compared to a baseline model, representative of standard dengue surveillance practice. Drought conditions were found to positively influence dengue relative risk at long lead times of up to 5 months, while excess rainfall increased the risk at shorter lead times between 1 and 2 months. The SPI averaged over a 6-month period (SPI-6), designed to monitor drought and extreme rainfall, better explained variations in dengue risk than monthly precipitation data measured in millimetres. Tmin was found to be a better predictor than mean and maximum temperature. Furthermore, including bidimensional exposure–lag–response functions of these indicators—rather than linear effects for individual lags—more appropriately described the climate–disease associations than traditional modelling approaches. In prediction mode, the model was successfully able to distinguish outbreaks from nonoutbreaks for most years, with an overall proportion of correct predictions (hits and correct rejections) of 86% (81%:91%) compared with 64% (58%:71%) for the baseline model. The ability of the model to predict dengue outbreaks in recent years was complicated by the lack of data on the emergence of new arboviruses, including chikungunya and Zika.

Conclusion
We present a modelling approach to infer the risk of dengue outbreaks given the cumulative effect of climate variations in the months leading up to an outbreak. By combining the dengue prediction model with climate indicators, which are routinely monitored and forecasted by the Regional Climate Centre (RCC) at the Caribbean Institute for Meteorology and Hydrology (CIMH), probabilistic dengue outlooks could be included in the Caribbean Health-Climatic Bulletin, issued on a quarterly basis to provide climate-smart decision-making guidance for Caribbean health practitioners. This flexible modelling approach could be extended to model the risk of dengue and other arboviruses in the Caribbean region.

Read the full publication at PLOS Medicine

 

 

 

 

 

 

Aedes control – image courtesy Mr. Dany Krom

GAINESVILLE, FL – New research co-authored by UF Geography’s Dr. Sadie Ryan and Ms. Cat Lippi sheds light on the climate suitability for Aedes aegypti and Aedes albopictus mosquitos and transmission rates of Zika, chikungunya, and dengue fever.

The study, published in PLOS Neglected Tropical Diseases compares new data driven models of Zika, chikungunya, and dengue fever transmission to real world measurements of human infections caused by bites from Aedes aegypti and Ae. Albopictus mosquitoes. These models confirm that temperature is the single most important factor for predicting the rate and geographic spread of epidemics of these mosquito-borne diseases. Temperature influences transmissibility in many ways – affecting the lifespan of an individual mosquito, and determining biting frequency and the reproductive rate of the virus within the mosquito.

The collaborative research team includes experts in epidemiology, public health, ecology, mathematical modeling, and geography, and was funded by a grant from the National Science Foundation’s Ecology and Evolution of Infectious Disease program (NSF-DEB 1518681).

Ryan Lab Fall 2016. Image courtesy Dr. Sadie Ryan.
Ryan Lab Fall 2016. Image courtesy Dr. Sadie Ryan.

This summer, Geography’s Ryan Lab and the Emerging Pathogens Institute were proud to host Lauren Fregosi as a summer research intern working on Dr. Sadie Ryan‘s National Science Foundation’s Ecology and Evolution of Infectious Diseases (NSF EEID) grant. The internship, which was offered through the NSF Research Experience for Undergraduates (REU) program, was focused on modelling approaches on the effects of climate, land use, and socioeconomic conditions on vector-borne disease transmission.

Ms. Fregosi is a native of Long Island’s south shore, and is a rising senior at Syracuse University (class of 2017), pursuing a bachelor’s degree in Biotechnology, with a minor in Applied Statistics, and conducting research at SU’s Falk School of Public Health. She was excited to work with the Ryan Lab because of her passionate interest in vectorborne disease control. This work built on her existing experience working on a project analyzing biting rates of different mosquito species and urbanization in Ecuador, at the Falk School of Public Health. Fregosi has enjoyed learning multiple strategies for organizing, analyzing, and describing datasets, in R, developing models in both R and GARP, and becoming well versed with GIS, and ArcGIS model builder.

When not polishing her GIS skills, Ms. Fregosi donates her free time volunteering at Syracuse’s Upstate Golisano Children’s Hospital and Habitat for Humanity. She also organizes phlanthropic activities, community projects, and fundraisers for her sorority.

The Department of Geography thanks Lauren for all of her hard work this summer, and wishes her luck in her continued studies!

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.