- Author: Kathy Keatley Garvey
The parallel, cluster-randomized, controlled trial revealed that a spatial repellent, currently under review by the World Health Organization (WHO), reduced human Aedes-borne virus infection by 34.1 percent.
“That is a significant statistical and public health reduction,” said Scott, an internationally recognized medical entomologist who retired from the UC Davis Department of Entomology and Nematology in 2015 but continues his scientific research on the ecology and epidemiology of dengue, a mosquito-borne viral infection transmitted mainly by A. aegypti. Dengue, one of the most rapidly increasing vector-borne infectious diseases, infects some 400 million people a year, with 4 billion people at risk annually.
The clinical study results mean that spatial repellents have “the potential to reduce a variety of vector-borne diseases, augment existing public health efforts, and can be an effective component in vector control intervention strategies,” Scott said.
The newly published research, “Efficacy of a Spatial Repellent for Control of Aedes-borne Virus Transmission: A Cluster-Randomized Trial in Iquitos, Peru,” appears in the Proceedings of the National Academy of Sciences (PNAS). The Bill and Melinda Gates Foundation funded the research in a grant to the University of Notre Dame (UND). Medical entomologist Nicole Achee, a research professor at UND, served as the project leader.
“To have shown a substantial public health impact at an endemic site, is rewarding,” said Scott, now a resident of Luck, Wis. “Our results provide valuable new data on mosquito control that will help to fill long-standing knowledge gaps and improve guidance for development of enhanced public health policy. Because literally billions of people around the globe are at risk of infection and disease from these viruses we are encouraged that results from our trial will contribute to improved health and well-being of so many people.”
Epidemiologist Amy Morrison, a 1996-2018 project scientist with the UC Davis Department of Entomology and Nematology and now with the UC Davis School of Veterinary Medicine's Department of Pathology, Microbiology and Immunology, served as the lead author of the PNAS paper. “This trial was the most logistically challenging field project I've ever participated in,” she said. “I led the field efforts in Iquitos, Peru where I have resided since 1998. Our research team continued to amaze me; they had to replace more than 20,000 products in more than 2,000 houses every 15 days and managed 80 percent coverage of participating houses. This type of vector control trial is very difficult to carry out so demonstrating protective efficacy is very gratifying.”
Achee said the Peru study outcomes “are a critical component to achieving our goals for supporting a WHO policy endorsement for spatial repellents. The reduction in Aedes-borne virus infection in at-risk participants seen in trial results have fundamentally contributed to the WHO encouraging further consideration for the use of this product class in public health worldwide. This is a historical milestone that was led by the UC Davis implementing team and I am thrilled to have been part of the collaborative effort."
Spatial repellents are “devices that contain volatile active ingredients that disperse in air,” the authors explained. “The active ingredients can repel mosquitoes from entering a treated space, inhibit attraction to human host cues, or disrupt mosquito biting and blood-feeding behavior and, thus, interfere with mosquito–human contact. Any of these outcomes reduce the probability of pathogen transmission.”
More than half of the world population is at risk for infection with viruses transmitted by Aedes mosquitoes, including include dengue, Zika, chikungunya, and yellow fever, the scientists wrote.
Vector interventions are needed for Aedes-borne viral (ABV) disease prevention “but their application is hindered by the lack of evidence proving they prevent infection or disease," they wrote. "Results from our ABV study will help guide public health authorities responsible for operational management and worldwide ABV disease control and incentivize new strategies for disease prevention.”
“The primary mosquito vector, Aedes aegypti, thrives in modern tropical urban environments. Despite decades of effort to control Ae. aegypti populations and prevent disease, the geographic range of illness and the viruses this mosquito transmits continue to expand,” they related. “Rigorously proven vector control interventions that measure protective efficacy against Aedes-borne viruses are limited to Wolbachia in a single trial in Indonesia and do not include any chemical interventions. Spatial repellents, a new option for efficient vector control, are designed to decrease human exposure to Aedes-borne viruses by releasing active ingredients into the air that disrupt mosquito–human contact and, thus, reduce the risk of human infection.”
The Iquitos trial is one of two trials recommended by WHO for assessing public health value and developing global health policy for the intervention class of spatial repellents. “Fully integrating vector control into Aedes-borne viral disease prevention programs requires quantitative guidance based on quantitative measures of the impact from each intervention component,” the authors wrote. “Ministries of Health, local to national governments, and nongovernmental organizations can use the Peru trial results as an evidence base for informed application of spatial repellents. Considering the growing public health threat from Aedes-borne viral disease, difficulties of developing vaccines against multiple viruses, and past poorly informed vector control failures, enhanced Aedes-borne viral disease prevention will benefit greatly from interventions, like the Peru trial, with proven public health value.
Thomas Scott. Scott, a member of three WHO committees and one of the world's Highly Cited Researchers for the third consecutive year, co-chairs a Lancet Commission that focuses on how prevention of viruses transmitted by Aedes mosquitoes. He served on the faculty of the Department of Entomology, University of Maryland, from 1983 to 1996 before joining the UC Davis entomology faculty as a professor of entomology and director of the Vector-Borne Disease Laboratory. Highly honored by his peers, Scott won the coveted Harry Hoogstraal Medal from the American Society of Tropical Medicine and Hygiene in 2018. He is a fellow of the American Society of Tropical Medicine and Hygiene, Entomological Society of America, and the American Association for the Advancement of Science. He holds bachelor and master's degrees from Bowling Green (Ohio) State University and a doctorate in ecology in 1981 from Pennsylvania State University.
Amy Morrison. Morrison, who holds a doctorate in public health from Yale University, with a concentration in epidemiology of infectious diseases, and a master's degree in public health from UCLA, has served as the principal investigator, co-principal investigator and a collaborator on a number of federally funded grants. She specializes in the epidemiology of tropical vector-borne diseases, with an emphasis on (1) arthropod vector ecology and dengue virus transmission dynamics and (2) spatial and temporal analyses using Geographic Information Systems.
As a project scientist, Morrison supervises multiple studies on A. aegypti and dengue virus transmission dynamics, including longitudinal cohort studies evaluating A. aegypti control interventions, and the role of human movement in dengue transmission dynamics in Iquitos, funded by National Institutes of Health, Military Infectious Disease Research Program and Bill and Melinda Gates Foundation. She is an active member of the American Mosquito Control Association, American Association for the Advancement of Science, Entomological Society of America, American Society of Tropical Medicine and Hygiene, and the Society of Vector Ecologists.
Nicole Achee. Achee is a research associate professor in the Department of Biological Sciences, UND, and holds a joint associate professor appointment in the Eck Institute for Global Health, UND. She worked as a medical entomologist in the international settings of Belize, Indonesia, Mexico, Nepal, Peru, South Korea, Suriname, Tanzania and Thailand. Her curriculum vitae includes principal investigator for large scale clinical trials in Peru and Indonesia. Both studies aimed “to generate evidence of the protective efficacy of spatial repellents for prevention of malaria and dengue human infections for use toward full World Health Organization public health policy recommendations,” she says on her website. Achee holds a doctorate in medical entomology from the Uniformed Services University of the Health Science, Bethesda, Md.
In addition to the Bill and Melinda Gates Foundation, the Iquitos project drew support from the Defense Threat Reduction Agency, Military Infectious Disease Research Program and the U.S. National Institute of Allergy and Infectious Diseases.
- Author: Kathy Keatley Garvey
Professor Scott, who now resides in Luck, Wis., is internationally known for his work on the ecology and epidemiology of dengue, a mosquito-borne viral infection transmitted mainly by Aedes aegypti.
Only 1 percent of researchers make the global list of Highly Recited Researchers, as announced by Clarivate. The Web of Science Group, the information and technology provider for the global scientific research community, annually honors the 1 percent of scientists whose publications are the most cited in scientific papers.
One in 1000. "Of the world's scientists and social scientists, Highly Cited Researchers truly are one in 1,000," according to the Web of Science website.
Scott is one of 14 researchers from UC Davis--and one of some 6660 worldwide--to achieve the 2021 honor.
Scott's 19 publications listed in the report have been cited a total of 402 times. His most cited publication: “The Current and Future Global Distribution and Population at Risk of Dengue,” published in Nature Microbiology in 2019.
“Being a Highly Cited Researcher means a lot to me because it's an objective measure of the extent to which the scientific community finds helpful the work that my colleagues and I did,” said Scott, who joined the UC Davis Department of Entomology (now the Department of Entomology and Nematology) in 1996. “ I was privileged to work with exceptionally smart, hard-working, and insightful people. We had a lot of fun, but we also took our science seriously. We challenged each other in constructive and collegial ways. We are proud of the results of our efforts.”
“Because I enjoy it, I am continuing to explore science and public health,” Scott said. “Presently, I am involved in a variety of activities that range from writing manuscripts to kicking off new studies to serving on scientific and public health policy projects and committees. “
Healthy Cites, Healthy People. Scott co-chairs a Lancet Commission that focuses on how prevention of viruses transmitted by Aedes mosquitoes fits into the growing Healthy Cities, Healthy People movement. Lancet Commissions are tasked with identifying the most pressing issues in science, medicine, and global health, with the aim of providing recommendations that change health policy or improve practice. “In this case, we are making the case for Cities without Aedes,” Scott said. "We aim to reduce the burden and threat from Aedes transmitted viruses through improved construction and management of modern urban environments that build Aedes mosquitoes out of cities and towns.”
Scott is a collaborator in a clinical trial designed to demonstrate and quantify the protective efficacy of a spatial repellent to reduce human mosquito transmitted virus infection in Sri Lanka. “This new project,” he said, “builds on a randomized controlled clinical trial that my colleagues I recently completed in Iquitos, Peru, which revealed a significant protective efficacy of a spatial repellent against human infection. Publication of those results a currently under review.”
Scott's other activities include being a scientific advisor for a clinical trial in Brazil that is testing the public health benefit of Wolbachia for prevention of viruses transmitted by Aedes mosquitoes. “The study will assess the efficacy of releasing Wolbachia-infected Aedes aegypti into the environment in reducing human virus infection compared to standard vector control measures alone,” he said.
Scott serves on three World Health Organization committees, “which I find particularly rewarding because of their potential to improve public health policy and thus global health.”
Among his other activities:
- Chair of a group that is writing a chapter on Dengue Vector Control Guidelines that will be included in the updated version of WHO guidelines for dengue diagnosis, treatment, prevention, and control.
- Co-chair of the Wolbachia Evidence Review Group. “Mosquitoes infected with the endosymbionic bacteria Wolbachia are designed to have reduced capacity to become infected with and transmit a variety of viruses, which is expected to reduce human disease,” Scott explains. “Results from our deliberations will help the World Health Organization to develop guidelines for member States on the application of this exciting new intervention strategy.”
- Member of the World Health Organization Technical Advisory Group on the Global Integrated Arboviruses Initiative. The Arbovirus Initiative focuses on strengthening the coordination, communication, capacity building,research, preparedness, and response needed to mitigate the growing risk of epidemics due to arthropod transmitted viral diseases. Scott describes it as “a collaborative effort between the World Health Emergency Program, the Department of Control of Neglected Tropical Diseases, and the Immunization, Vaccines, and Biological Department at WHO. Members of the Technical Advisory Group have a broad range of expertise (clinical management, diagnostics, epidemiology, vector control, virology, vaccines, and travel medicine) and serve in an advisory capacity to WHO with a focus on essential and strategic guidance on management of disease. Our current focus is finalizing the Global Integrated Arboviruses Initiative, which will be presented to the World Health Assembly for review and approval.”
Scott, who holds bachelor and master's degrees from Bowling Green (Ohio) State University, received his doctorate in ecology in 1981 from Pennsylvania State University and did postdoctoral research in epidemiology at Yale University School of Medicine's Arbovirus Research Unit, part of the Department of Epidemiology and Public Health. He served on the faculty of the Department of Entomology, University of Maryland, from 1983 to 1996 before joining the UC Davis entomology faculty as a professor of entomology and director of the Vector-Borne Disease Laboratory. He was acting director of the UC Davis Center for Vector-Borne Research from 1996 to 1999, and director of the UC Davis Arbovirus Research Unit (2001-2003). He was selected vice chair of the Department of Entomology in 2006, serving until 2008.
Highly honored by his peers, Scott won the coveted Harry Hoogstraal Medal from the American Society of Tropical Medicine and Hygiene in 2018. His other honors include fellow of three organizations: American Society of Tropical Medicine and Hygiene (2014), Entomological Society of America (2010), and the American Association for the Advancement of Science (2008). He was named a UC Davis distinguished professor in 2014. In 2015, he won the Charles W. Woodworth Award, the highest honor awarded by the Pacific Branch of the Entomological Society of America.
Who's Who. The methodology that determines the “who's who” of influential researchers draws on the data and analysis performed by bibliometric experts and data scientists at the Institute for Scientific Information at Clarivate. It also uses the tallies to identify the countries and research institutions where these citation elite are based.
The complete list of UC Davis-affiliated scientists listed in the 2021 Highly Cited Researchers
- Andreas Bäumler, Medical Microbiology and Immunology, School of Medicine
- Eduardo Blumwald, Plant Sciences, College of Agricultural and Environmental Sciences
- Siobhan Brady, Plant and Animal Science, College of Agricultural and Environmental Sciences
- Mariana Byndloss, formerly with Medical Microbiology and Immunology, School of Medicine
- Magdalene Cerda, formerly with Emergency Medicine, UC Davis Health System
- Alan Crozier, Nutrition, College of Agricultural and Environmental Sciences
- Kathryn Dewey Nutrition, College of Agricultural and Environmental Sciences
- Jonathan Eisen, Evolution and Ecology, Medical Microbiology and Immunology, Genome Center, Center for Population Biology
- Oliver Fiehn, Genome Center
- Carlito Lebrilla, Chemistry, College of Letters and Science
- David A. Mills, Food Science and Technology, College of Agricultural and Environmental Sciences
- Sally Rogers, Psychiatry and Psychology, UC Davis Health System
- Thomas W. Scott,Entomology and Nematology, College of Agricultural and Environmental Sciences
- Andrew Sih, Environmental Science and Policy, College of Agricultural and Environmental Sciences
- Author: Kathy Keatley Garvey
The 11 scientists rank in the top 1 percent by citations, which represent how often their papers have been cited in other scientific papers.
Scott, who joined the UC Davis faculty in 1996, has published 288 papers to date. His total number of citations: more than 33,500. He is internationally known for his work on the ecology and epidemiology of dengue, a mosquito-borne viral infection transmitted mainly by Aedes aegypti.
“Although I retired from UC Davis in 2015, I have continued to carry out research just as I had previously,” Scott said. “In reality, I retired from UC Davis, but I did not retire from science.”
Scott focuses his research on epidemiology of mosquito-borne diseases, mosquito ecology, evolution of mosquito-pathogen interactions, and evaluation of novel products and strategies for disease control.
“I aim to generate the detailed, difficult to obtain data that are necessary for assessing current recommendations for disease prevention, rigorously testing fundamental assumptions in public health policy, and developing innovative, cost, and operationally effective strategic concepts for prevention of mosquito-borne disease.”
Scott has remained active on a variety of fronts. In 2015, he was in the early stages of two large grants (National Institutes of Health Program Project grant “Quantifying Heterogeneities in Dengue Virus Transmission Dynamics” and a sub-award from a Bill and Melinda Gates grant, “Spatial Repellent Products for Control of Vector-Borne Diseases”), which he continued to run and manage through the Department of Entomology and Nematology.
“So, I had plenty of support (more than $10 million) to continue my work,” he said. Both projects took place in Iquitos, Peru, and were jointly led with his long-term UC Davis collaborator, Amy C. Morrison, who is in the Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine.
The Gates grant was a clinical trial to determine whether and to what extent a chemical that repelled mosquitoes would reduce a person's risk of dengue or Zika virus infection. Scott served as the project leader for the Iquitos trial. “Earlier this year we determined that it had a big protective effect,” he related. “We are currently writing that manuscript.”
“Both of those grants ended earlier this year, but we still have a lot of work to do and will be busy for the next couple of years writing papers about those projects,” Scott said. He is currently working as a consultant in a follow-up study on spatial repellents for dengue prevention that will begin in Sri Lanka during 2021.
“Prior to and after retirement, I worked closely with the World Health Organization (WHO), where I served on numerous committees,” Scott related. He chaired the Vector Control Advisory Group, co-chaired the Global Vector Control Response, chaired the Emergency Response Consultation for Zika Virus, chaired the Technical Working Group for Dengue, served on the International Health Regulators Roster of Experts, and co-authored the updated version of WHO's dengue management and control guidelines. He recently applied for membership on the WHO Expert Advisory Group on Arboviruses.
“Working with WHO is important to me because at this stage of my career, being able to translate my science experience into improved quality of life, that is, improved public health policy, for other people, many of whom live in poverty, is the most meaningful thing I can do.”
Scott, who holds bachelor and master's degrees from Bowling Green (Ohio) State University, received his doctorate in ecology in 1981 from Pennsylvania State University and did postdoctoral research in epidemiology at Yale University School of Medicine's Arbovirus Research Unit, part of the Department of Epidemiology and Public Health. He served on the faculty of the Department of Entomology, University of Maryland, from 1983 to 1996 before joining the UC Davis entomology faculty as a professor of entomology and director of the Vector-Borne Disease Laboratory. He was acting director of the UC Davis Center for Vector-Borne Research from 1996 to 1999, and director of the UC Davis Arbovirus Research Unit (2001-2003). He was selected vice chair of the Department of Entomology in 2006, serving until 2008.
Highly honored by his peers, Scott won the coveted Harry Hoogstraal Medal from the American Society of Tropical Medicine and Hygiene in 2018. His other honors include fellow of three organizations: American Society of Tropical Medicine and Hygiene (2014), Entomological Society of America (2010), and the American Association for the Advancement of Science (2008). He was named a UC Davis distinguished professor in 2014. In 2015, he won the Charles W. Woodworth Award, the highest honor awarded by the Pacific Branch of the Entomological Society of America.
Other UC Davis scientists listed as Highly Cited Researchers include five others from the College of Agricultural and Environmental Sciences: Eduardo Blumwald and Jorge Dubcovsky, both from Plant Sciences; Alan Crozier, Nutrition; David A. Mills, Food Science and Technology; and Andrew Sih, Environmental Science and Policy.
- Author: Kathy Keatley Garvey
Scott, internationally known for his work on the ecology and epidemiology of dengue, received the award "for his outstanding contributions to the study of mosquito ecology, evolution of mosquito-virus interactions, epidemiology of mosquito-borne disease and evaluation of novel products and strategies for mosquito control and disease prevention."
He focuses his work on contributing to improved public health in the United States and in the developing world, where resources are inadequate and help is desperately needed.
The coveted ASTMH award memorializes parasitologist-entomologist Harry Hoogstraal (1917-1986), a global authority on ticks and tick-borne diseases.
Scott, who joined the UC Davis faculty in 1996, received his bachelor and master's degrees from Bowling Green (Ohio) State University, and his doctorate in ecology in 1981 from Pennsylvania State University. He did postdoctoral research in epidemiology at Yale University School of Medicine's Arbovirus Research Unit, part of the Department of Epidemiology and Public Health.
Scott served on the faculty of the Department of Entomology, University of Maryland, from 1983 to 1996 before joining the UC Davis entomology faculty as a professor of entomology and director of the Vector-Borne Disease Laboratory. He was acting director of the UC Davis Center for Vector-Borne Research from 1996 to 1999, and directed the UC Davis Arbovirus Research Unit from 2001 to 2003. He served as vice chair of the Department of Entomology from 2006 to 2008.
In 2014, Scott was selected a “distinguished professor,” an honorary title bestowed by the provost “to recognize outstanding faculty in the professional series who have achieved the highest level of scholarship.”
Highly honored by his peers, Scott is a fellow of three organizations: American Society of Tropical Medicine and Hygiene (2014), Entomological Society of America (2010), and the American Association for the Advancement of Science (2008). In 2015, he won the Charles W. Woodworth Award, the highest honor awarded by the Pacific Branch of the Entomological Society of America.
Scott is the fifth medical entomologist from UC Davis to receive the Harry Hoogstraal Award since it was first presented in 1987. Other UC Davis recipients:
- 2012: William Reisen, director of the Center for Vectorborne Diseases (CVEC)
- 2007: Bruce Eldridge, former director of the statewide UC Mosquito Research Program and emeritus professor of entomology at UC Davis
- 2005: Robert Washino, emeritus professor and former chair of the UC Davis Department of Entomology
- 2004: John Edman, former director of CVEC and emeritus professor of entomology
- Author: Kathy Keatley Garvey
The distinction recognizes outstanding Senate faculty who have achieved the highest level of scholarship. "These are scholars whose work has been internationally recognized and whose teaching performance is excellent," according to the website.
Leal, former professor and chair of the UC Davis Department of Entomology, serves as a mentor in the campuswide Research Scholars Program in Insect Biology (RSPIB), launched in 2011 and administered by UC Davis Department of Entomology and Nematology faculty members professor Jay Rosenheim, associate professor Louie Yang and assistant professor Joanna Chiu.
RSPIB aims to provide academically strong and highly motivated undergraduates with a multi-year research experience that cultivates skills that will prepare them for a career in biological research. The annual deadline for undergraduates to apply is April 10.
Leal joins five other current or former faculty members of the UC Davis Department of Entomology and Nematology with the “distinguished professor” title: nematologists Howard Ferris and Harry Kaya and entomologists Bruce Hammock, Frank Zalom, Thomas Scott (now emeritus) and James R. Carey. Most are affiliated with RSPIB: Leal, insect physiology; Hammock, insect biochemistry; Zalom, integrated pest management, and Carey, insect demography.
Leal serves as co-chair the International Congress of Entomology (ICE) meeting, to take place Sept. 25-30, 2016 in Orlando, Fla.
