Medical entomologist Thomas Scott

It's well deserved!

Scott, a UC Davis distinguished professor who officially retired in 2015, is internationally known for his work on the ecology and epidemiology of dengue, a mosquito-borne viral infection transmitted mainly by Aedes aegypti.  He now resides in Luck, Wis., where his wife's family is from.

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.

"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.” 

A street scene in Iquitos, Peru, a city where UC Davis medical entomologist Thomas Scott worked.

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.” 

“In addition to the clinical trial, my colleagues and I are publishing a series of papers from Iquitos that examine the role of people with in-apparent and mild infections in virus transmission. By accounting for factors underlying variation in each person's contribution to transmission we will be able to better determine the type and extent of effort needed to prevent disease.” 

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.”

Challenging and Rewarding. “I am excited about and enjoy all these activities,” the medical entomologist commented. “They are challenging and rewarding extensions of the work I have done for that past 40 years.” 

Sylvia Fischer of the Buenos Aires, Argentina

Fischer is a member of the Mosquito Research Group, Department of Ecology, Genetics and Evolution.

Her seminar, open to all interested persons, begins at 4:10 p.m., Pacific Time. She will be introduced by UC Davis doctoral student Erin Taylor Kelly of the laboratory of medical entomologist-geneticist Geoffrey Attardo. The Zoom link is https://ucdavis.zoom.us/j/99515291076. 

"The mosquito Aedes aegypti, vector of dengue and other arboviruses, has recently expanded its distribution towards colder climate regions," Fischer says in her abstract. "This might be favored by an adaptation of the populations to local conditions. We explore the larval tolerance to low temperatures and the photoperiod induced embryonic diapause as possible mechanisms occurring in temperate Argentina."

"My main research interest is on mosquito ecology, and my current project aims to analyze the effects of environmental conditions (photoperiod, temperature, humidity) and resources (larval food) on the fitness of Aedes aegypti," she writes on ResearchGate. "I am also interested in human caused environmental change and its consequences on vector borne diseases."

She is a member of the 

Fischer recently co-authored a research paper on Behavior of Aedes albifasciatus (Diptera: Culicidae) larvae from eggs with different dormancy times and its relationship with parasitism by Strelkovimermis spiculatus (Nematoda: Mermithidae).

A. aegypti is also known as the yellow fever mosquito. Kelly, who is hosting the seminar, studies the mosquito in the Attardo lab. She won a first-place award at the Entomological Society of America meeting last November with her poster, “Metabolic Snapshot: Using Metabolomics to Compare Near-Wild and Colonized Aedes aegypti.” She competed in the Physiology, Biochemistry and Ecology Section.  (See https://bit.ly/3HJR0IF). 

Fischer's talk meshes with the work of the Geoffrey Attardo laboratory. In one of his research projects, Attardo investigates the threat of these invasive mosquitoes, which have gained a foothold and spread throughout the state, putting California at risk for Aedes-vectored diseases such as dengue, chikungunya, Zika and yellow fever. Attardo studies the prevalence and physiology of insecticide resistance in Californian populations and evaluates the use of genetic markers to predict insecticide resistance and to track movement of genetically independent populations of aegypti throughout the state. Attardo and his lab are also currently developing novel biochemically oriented methods of insecticide resistance quantification to identify compounds that mosquito abatement districts can use for monitoring, and to define the biochemical pathways required to maintain this problematic adaptation. 

The department's weekly seminars, held at 4:10 p.m. on Wednesdays, are coordinated by nematologist Shahid Siddique, who may be emailed at ssiddique@ucdavis.edu with any technical questions.

Geoffrey "Geoff" Attardo (Photo by Lindsay Mack)

By Geoff Attardo
Assistant Professor of Entomology and Nematology at UC Davis 

California's changing climate is creating a myriad of public health concerns. Wildfires, intense heatwaves, and a drought are the most readily apparent. However, increasingly temperate winters are also facilitating the spread of invasive disease-spreading mosquitoes throughout the state. Just as our fire authorities need a robust set of tools to address wildfires, it is critical that mosquito control and public health professionals have a wide range of tools to protect Californians from mosquito-borne diseases.

The growing presence of Aedes aegypti mosquitoes, which can transmit the viruses that cause Zika, dengue, chikungunya, and yellow fever as well as the parasite that causes heartworm in pets, is a major public health threat. In 2013 this invasive species was detected in the Central Valley and has been found in California every year since. These mosquitoes cohabitate with humans and often hitchhike facilitating their spread.

Aedes aegypti lay eggs in flowerpots, water storage containers or anything capable of holding small amounts of water. Part of the problem, as highlighted in our research in Frontiers in Tropical Diseases, is that these mosquitoes have cryptic breeding sites in residential areas where mosquito control agencies can't easily inspect and treat.

In addition, their eggs can dry out and then hatch when rehydrated. In fact, when Aedes aegypti were detected in 2014 in the city of Exeter there was a large eradication effort. The effort appeared successful, as they were no longer detectable in 2015. Yet, the mosquitoes were detected in Exeter again in 2018. The unique biology of this invasive species has allowed it to expand its geographical range and today they are present in more than 300 cities in California.

Another key factor is their inherent resistance to a class of insecticides called pyrethroids, which have been a mainstay for adult mosquito control because they have low toxicity to humans and other animals. Work from our lab and the California Department of Public Health found increasing insecticide resistance in these mosquitoes (Parasites and Vectors) which limits the ability of mosquito control agencies to act against adult mosquitoes in a time of crisis.

In order to protect public health, mosquito control agencies need effective tools in their toolbox. One innovative approach takes advantage of the fact that male mosquitoes do not bite; only female mosquitoes bite and can spread viruses. This approach works by releasing sterile male Aedes aegypti mosquitoes. These male-only mosquitoes carry a self-limiting gene that prevents their female offspring from surviving. When they mate with females, this reduces the abundance of biting females in the next generation. One of the benefits of this species-specific approach is that it only targets the Aedes aegypti mosquito. This means that wildlife, such as butterflies and bees, are unharmed.

The public health threat of Aedes aegypti cannot be overstated. The World Health Organization (WHO) estimates that dengue fever causes approximately 40,000 deaths a year and Zika virus, of which there were over 5,100 symptomatic domestic cases in 2016, is known to cause serious birth defects and miscarriage as well as Guillain-Barré syndrome. The WHO also said “the potential public health benefit of practical and effective new tools to reduce or even eliminate diseases such as malaria and dengue is clear and widely recognized.”

A company called Oxitec is working with government agencies to bring its innovative mosquito control technology to the U.S. In August, they announced they are seeking regulatory approvals to expand their pilot program to bring their Friendly™ Aedes aegypti technology to California. I encourage regulators to allow the company to work with mosquito control agencies to determine the technology's effectiveness in California.

It's clear that we need efficient mosquito control tools, and we cannot wait until we have a public health emergency to act. As we have seen with the COVID pandemic it is critical to have an infrastructure in place, especially one that includes innovative – and proven – technologies, to help public health and mosquito controls stay ahead of the curve. 

Ah, Saturday, April 17. It's the 107th Annual UC Davis Picnic Day! What's a picnic without bugs?

This year's event, all virtual, is themed "Discovering Silver Linings," and you can do just that by watching the pre-recorded videos and by participating in the Zoom sessions. Check out the Picnic Day schedule of events which include entomological exhibits and talks from the UC Davis Department of Entomology and Nematology, Bohart Museum of Entomology and the UC Davis Graduate Student Association. 

New additions to the line-up (featured on the Bohart Museum of Entomology website), involve what you could call "The good, the bad and the bugly." Blue orchard bees, tsetse flies and mosquitoes are spotlighted in UC Davis research-based  videos created by KQED's Deep Look series and presented by PBS Digital Studios. Each runs about four minutes. 

Here are the KQED productions:

• Watch this Bee Build Her Bee-Jeweled Nest, featuring blue orchard bees, the project of UC Davis doctoral student Clara Stuligross. 
  
  
• A Tsetse Fly Births One Enormous Milk-Fed Baby, showcasing the work of medical entomologist Geoffrey Attardo, assistant professor, UC Davis Department of Entomology and Nematology. 
  
  
• This Dangerous Mosquito Lays Her Armored Eggs--in Your House, involving the Aedes aegypti mosquitoes that the Attardo lab studies. 

Clara Stuligross, Doctoral Student

Clara Stuligross, doctoral student

They exposed the bees to the neonicotinoid insecticide imidacloprid, widely used in agriculture, and found that the combined threats—imidacloprid exposure and the loss of flowering plants—reduced the bee's reproduction by 57 percent, resulting in fewer female offspring.

Other scientists have conducted similar research on honey bees, but this is the first comparable research on wild bees in field or semi-field conditions. The blue orchard bee, nicknamed BOB, is a dark metallic mason bee, smaller than a honey bee. It is prized for pollinating almond, apple, plum, pear, and peach trees. California almond growers often set up bee boxes or "bee condos" for blue orchard bees to aid in honey bee pollination. In the wild, the bees nest in reeds or natural holes. 

Update? "We are currently working on a follow-up study to investigate potential carryover effects of past insecticide exposure on the same bee population, as well as how repeated pesticide exposure over multiple years impacts bee population growth," Stuligross said today.

Geoffrey Attardo, Medical Entomologist-Geneticist 

Geoffrey Attardo, medical entomologist-geneticist

What many people do not know: "Female tsetse flies carry their young in an adapted uterus for the entirety of their immature development and provide their complete nutritional requirements via the synthesis and secretion of a milk like substance," Attardo says. 

Attardo led landmark research published Sept. 2, 2019 in the journal Genome Biology that provides new insight into the genomics of the tsetse fly. The researchers compared and analyzed the genomes of six species of tsetse flies. Their research could lead to better insights into disease prevention and control.

The Deep Look episode on mosquitoes, "This Dangerous Mosquito Lays Her Armored Eggs-- in Your House,"  deals with the ability of Aedes aegypti eggs to survive out of water.  Wrote the producers: "The Aedes aegypti mosquito, which can transmit dengue fever and Zika, makes a meal of us around our homes. And her eggs are hardy. They can dry out, but remain alive for months, waiting for a little water so they can hatch into squiggly larvae."