- Author: Kathy Keatley Garvey
UC Davis medical entomologist-geneticist Geoffrey Attardo, a global authority on tsetse flies, serves as the principal investigator of a research project at the Lawrence Berkeley National Laboratory (Berkeley Lab) that involves scanning the entire reproductive cycle of the fly.
Attardo and other members of the research team are exploring the intact organs and tissues of tsetse flies using a powerful 3D X-ray imaging technique. The study, “Unraveling Intersexual Interactions in Tsetse”), is funded by the National Institute of Allergy and Infectious Diseases (NAIAD) of the National Institutes of Health.
“We started this project in 2019 and the work is ongoing,” said Attardo, an assistant professor in the UC Davis Department of Entomology and Nematology and chair of the Designated Emphasis in the Biology of Vector Borne Diseases. “We actually have scans of flies through the entire reproductive cycle, however, the segmentation is ongoing. We are working on developing ways to train artificial intelligence based software to assist us with the tissue segmentations.”
The tsetse fly transmits the parasite that causes the deadly human and animal trypanosomiasis, better known as African sleeping sickness, says Attardo, who is featured in a recently posted article, "A Detailed Look Inside Tsetse Flies," on the Berkeley Lab website. (See YouTube)
“This specialized reproductive biology has required dramatic modifications to the morphology of the reproductive organs in these and related flies,” according to the Berkeley Lab News Center. “Here, we use phase contrast micro-Computed Tomography (Micro-CT) to visualize these adaptations in three dimensions for the first time. These adaptations include cuticular modifications allowing increased abdominal volume, expanded abdominal and uterine musculature, reduced egg development capacity, structural features of the male seminal secretions and detailed visualization of the gland responsible for synthesis and secretion of “milk” to feed intrauterine larvae. The ability to examine these tissues within the context of the rest of the organ systems in the fly provides new functional insights into how these changes have facilitated the evolution of the mating and reproductive biology of these flies.”
“The imaging technique provided new insights into how the flies' specialized biology governs mating and reproductive processes, including female flies' unique lactation and their delivery of a single fully developed larvae per birthing cycle – whereas most other insect species lay eggs,” according to the article. “The ALS (National Laboratory Advanced Light Source) produces X-rays and other forms of light for a broad range of simultaneous scientific experiments.”
The parasite invades the central nervous system and disrupts the sleep cycle, he says. “If not treated, the disease can result in progressive mental deterioration, coma, systemic organ failure and death.” An estimated 65 million people in 36 countries in sub-Saharan Africa are at risk for the deadly disease, according to the World Health Organization.
Attardo led a study, published in September 2020 in the journal Insects, detailing the ALS imaging work. The article, “Interpreting Morphological Adaptations Associated with Viviparity in the Tsetse Fly Glossina morsitans (Westwood) by Three-Dimensional Analysis,” received widespread attention. ALS experiments allow the researchers to create a detailed 3D visualizatiaon of the reproductive tissues without dissection and staining processes that introduce damage to the delicate samples.
“We want to understand what changes are happening during this process, how the process is being mediated, and if it can be manipulated to artificially repress females in the wild from mating,” Attardo told the Berkeley Lab News Center.
The Berkeley Lab is a multiprogram science lab in the national laboratory system supported by the U.S. Department of Energy through its Office of Science.
In his UC Davis lab, Attardo researches one of 35 tsetse fly species, Glossina morsitans morsitans, which prefers feeding on cattle to humans. Its strong mouthparts can easily puncture the tough cattle hide. In his lab, he feeds them warm cow blood.
As Attardo says on his website: "Arthropod vectored diseases cause more than 1 billion cases of illness and over 1 million deaths in humans each year. My work centers on understanding the reproductive biology of insect vectors of human disease. The goal of this work is to develop a detailed understanding of the molecular biology and physiology of these insects and to exploit this information to control these insects and the diseases they transmit. I use molecular biology and biochemical techniques in my research to address these questions. I also incorporate new technologies such as high throughput DNA sequencing and metabolomics which expand beyond the capabilities of traditional molecular techniques to understand the biology of these organisms at a systems level."
The UC Davis scientist hopes "to use the knowledge gained from these studies to improve current vector control strategies and to develop new strategies that disrupt the reproduction of these disease vectors."
Attardo holds a doctorate in genetics from Michigan State University, where he researched the molecular biology of mosquito reproduction in the lab of Alexander. Prior to joining the UC Davis faculty in 2017, Attardo worked for 13 years in the Department of Epidemiology of Microbial Diseases at the Yale School of Public Health, first as a postdoctoral associate and then as a research scientist studying the reproductive biology of tsetse flies.
- 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
But if you're UC Davis entomologist-geneticist Geoffrey Attardo, you do.
He led landmark research published Sept. 2 in the journal Genome Biology that provides new insight into the genomics of the tsetse fly, an insect that transmits the parasite that causes human and animal trypanosomiasis. In humans, it's commonly known as sleeping sickness, and if not treated, it's fatal.
Tsetse flies, Glossina sp., are of great medical and economic importance, wrote Attardo and co-authors Adly M. M. Abd-Alla of the Insect Pest Control Laboratory, Division of Nuclear Techniques in Food and Agriculture, Vienna, Austria, and Serap Aksoy of the Yale School of Public Health, New Haven, Conn. They related that since the implementation of surveillance and record-keeping in the 20th century, “millions of people in sub-Saharan Africa” have died from sleeping sickness.
Their research compares and analyzes the genomes of six species of tsetse flies and could lead to better insights into disease prevention and control. “It was a behemoth project, spanning six to seven years,” said Attardo, an assistant professor in the Department of Entomology and Nematology. “This project represents the combined efforts of a consortium of 56 researchers throughout the United States, Europe, Africa and China.”
“The aim of these studies,” the authors wrote, “was to generate and mine the genomic sequences of six species of tsetse flies with different ecological niches, host preferences, and vectorial capacities. The goals of the analyses performed here are to identify the novel genetic features specific to tsetse flies and to characterize the differences between the Glossina species to correlate the genetic changes with phenotypic differences in these divergent species.”
“Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control,” the scientists concluded. “They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.”
Attardo, who joined the UC Davis faculty in 2017 after serving 13 years with the Yale School of Public Health, said the massive research project involved “the complete sequencing and assembly of six Glossina species, including the two primary vectors of human African tryapnosomiasis, three major vectors of animal trypanosomiasis and one ancestral tsetse species which demonstrates some resistance to the species of trypanosomes responsible for human and some animal forms of the disease.”
- A clearer definition of the Glossina phylogenetic tree and placement of a controversial species.
- Identification of rapidly evolving regions of the tsetse genome relative to Drosophila.
- Identification of Glossina specific genes and their functions as well as expansions and contractions of gene families in tsetse relative to other flies.
“We discuss the functional implications of these changes and how they relate to tsetses' physiological adaptations and evolutionary history,” Attardo noted.
“We discovered that the rhodopsin gene family which is associated with vision/color detection shows conservation in motion detection and tracking associated genes.” Attardo said. “However, the gene coding for the protein that detects blue wavelengths is divergent relative to houseflies and shows the highest variance between Glossina species of all the rhodopsin genes. This is significant as the color blue is used as an attractant to bring tsetse into the traps used for control. It suggests that different species may be tuned/attracted to different wavelengths of blue.”
They also analyzed the genes associated with tsetse immunity and the relative differences in comparison with houseflies and fruit flies. “We see many immune genes missing in Glossina and increased copy numbers of genes associated with negative regulation of immune function. We think this may be associated with the evolution of obligate symbiosis as a way to protect their symbionts.”
“We also found extreme conservation of milk proteins between all sequenced species,” the UC Davis medical entomologist said. “On the flip side, male reproductive proteins (seminal proteins) appear to be very rapidly evolving relative to the rest of the genome. The copy numbers of these genes also change significantly between species.”
The scientists also found an overall reduction of olfactory associated genes and protein modifications specific to salivary proteins in the two species that vector human trypanosomiasis.
In 1995, the World Health Organization (WHO) estimated that 60 million people were at risk of sleeping sickness, with an estimated 300,000 new cases per year in Africa, and fewer than 30,000 cases diagnosed and treated. Due to increased control, only 3796 cases were reported in 2014, with less than 15,000 estimated cases, according to WHO statistics.
The parasitic disease “mostly affects poor populations living in remote rural areas of Africa,” according to WHO. “Untreated, it is usually fatal. Travelers also risk becoming infected if they venture through regions where the insect is common. Generally, the disease is not found in urban areas, although cases have been reported in suburban areas of big cities in some disease endemic countries.”
Several National Institutes of Health (NIH) grants, awarded to Attardo and Aksoy, funded the research. They also drew funding from the McDonnell Genome Institute at Washington University School of Medicine; the National Research Foundation, the Swiss National Science Foundation, and the Slovak Research and Development Agency.
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/span>- Author: Kathy Keatley Garvey
The event is free and open to the public and will be hosted by Jared Shaw of the UC Davis College of Letters and Science.
“It is actually going to be a very basic talk aimed at lay audiences and kids,” Attardo says. “I'll be talking about my background, how I became an entomologist and how I ended up working on tsetse flies. Then I am going to discuss the life history of tsetse flies, where they can be found, why they are of medical importance and how their reproductive biology differs so dramatically from other flies that people are familiar with. My plan is to go over their reproductive cycle, how they develop intrauterine larvae, the reproductive adaptations that allow them to perform this feat and then go over what we know about tsetse milk secretions and how they compare to mammalian milk in terms of nutritional content.”
“The aim is for it to be very informal, with very little scientific jargon and to be discussion-oriented so that there is lots of questions and answers. I am also bringing some items from the lab that can be passed around the audience for show and tell (homemade tsetse cages, the blood feeding system we use to feed the flies and some tsetse flies preserved in alcohol).
Attardo focuses his research on numerous aspects of the physiology of tsetse fly reproduction, with the goal to identify and understand key aspects of its reproductive biology. He joined the UC Davis Department of Entomology and Nematology in 2017 from the Yale University School of Public Health, New Haven, Conn., where he researched tsetse flies in the lab of Serap Aksoy.
Attardo considers the tsetse fly "one of the champions of the insect world."
"In addition to being vectors of a deadly disease, Trypanosomiasis, these flies have undergone amazing alterations to their physiology relative to other insects," he says. "Some examples of this are their ability feed exclusively on blood, their obligate relationship with a bacterial symbiont, the fact that they lactate and that they give birth to fully developed larval offspring."
Attardo is the co-author of Adenotrophic Viviparity in Tsetse Flies: Potential for Population Control and as an Insect Model for Lactation, published in January 2015 in the Annual Review of Entomology.
- 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