Mosquito researcher Maria Onyango, a postdoctoral associate at the New York State Department of Health, Albany, N.Y., will speak on "The Impact of Zika Virus Infection on the Metabolites and Microbiome of Aedes albopictus" from 4:10 to 5 p.m. The Zoom seminar is open to all interested persons; click here for the form to register and obtain the Zoom link.
Aedes albopictus, known as the Asian tiger mosquito, is a close relative of Aedes aegypti, the yellow fever mosquito. Both invasive species are moving through California. (See California report of the two species, and the Center for Disease Control and Prevention's estimate potential range of the two species in the United States.)
Medical entomologist-geneticist Geoffrey Attardo of the UC Davis Department of Entomology and Nematology, who collaborates with Onyango, will host the seminar.
"Dr. Maria Onyango works on the biology underlying interactions between arboviruses (Zika virus), vector mosquitoes and the associated microbiome," Attardo said.
Aedes aegypti Detected in Yolo County
The Sacramento-Yolo Mosquito and Vector Control District recently announced the detection of Aedes aegypti in Yolo County: an adult female found Sept. 15 in a trap near East and Main streets, Winters, and an adult female found in in a trap at Pioneer Park near El Macero, Davis, on Sept. 30.
Aedes aegypti, a day-biting mosquito originating from the forests of Uganda, can transmit the Zika virus, yellow fever, dengue, and chikungunya. However, California has no documented cases of this species transmitting the Zika virus, dengue or chikungunya.
Attardo related that the first detection of Aedes aegypti in California occurred in 2013 and was described in these papers:
- Metzger, M.E.; Hardstone Yoshimizu, M.; Padgett, K.A.; Hu, R.; Kramer, V.L. Detection and Establishment of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) Mosquitoes in California, 2011-2015. J. Med. Entomol. 2017, 54, 533–543, doi:10.1093/jme/tjw237.
- Gloria-Soria, A.; Brown, J.E.; Kramer, V.; Hardstone Yoshimizu, M.; Powell, J.R. Origin of the dengue fever mosquito, Aedes aegypti, in California. PLoS Negl. Trop. Dis. 2014, 8, e3029, doi:10.1371/journal.pntd.0003029.
"Since then it has been determined that there have likely been at least two separate introductions of Aedes into California--possibly three but that requires additional study," Attardo says. "The result of this is that there are two genetically distinct populations of Aedes in California. One is based in Southern California in the Greater Los Angeles area as well as areas to the East, like Riverside and Coachella valleys. The second population is distributed throughout the Central Valley. These two populations are genetically distinct and we have developed a genetic assay to differentiate the two populations. We have been working with local abatement agencies (Winters, Sacramento/Yolo and Shasta counties) to test their collected mosquitoes to determine which population they resemble at the genetic level. Each year has shown Aedes aegypti spreading farther into parts of California where it has never been seen before."
- Pless, E.; Gloria-Soria, A.; Evans, B.R.; Kramer, V.; Bolling, B.G.; Tabachnick, W.J.; Powell, J.R. Multiple introductions of the dengue vector, Aedes aegypti, into California. PLoS Negl. Trop. Dis. 2017, 11, e0005718, doi:10.1371/journal.pntd.0005718.
- Lee, Y.; Schmidt, H.; Collier, T.C.; Conner, W.R.; Hanemaaijer, M.J.; Slatkin, M.; Marshall, J.M.; Chiu, J.C.; Smartt, C.T.; Lanzaro, G.C.; et al. Genome-wide divergence among invasive populations of Aedes aegypti in California. BMC Genomics 2019, 20, 204, doi:10.1186/s12864-019-5586-4.
"We recently ran our genetic test on mosquitoes that we collected from two different sites in Citrus Heights (divided by Route 80) and actually found that the two groups appear to represent both the Greater Los Angeles and the Central Valley populations, with each group specific to one side or the other of Route 80," Attardo said. "This is unpublished data and we are continuing to process additional samples of collected Aedes to reinforce these findings and understand the dynamics of how these mosquitoes are spreading."
The data suggests "that both populations are moving throughout California and are possibly being facilitated by human activities," Attardo said. "Aedes aegypti which was originally a mosquito that developed in tree holes has evolved to be a very human centric mosquito that has learned to thrive in man-made breeding sites. This may be the key to their success and their ability to move so quickly throughout the state."
Attardo emphasized that "these mosquitoes do not naturally carry these viruses and must acquire them by blood feeding on an infected person, successfully developing an infection and then biting another person. So far there have been no outbreaks of these diseases, but now that Aedes aegypti is here, the potential for an outbreak of dengue, Zika, chikungunya or yellow fever is a possibility. Infected people coming from countries where these viruses are endemic could serve to seed the viruses into Californian populations of Aedes which would obviously be a bad thing. The ongoing environmental changes resulting from climate change will likely allow these mosquitoes and others to move into previously uninhabitable areas and it is going to significantly change how we assess risk and management of mosquito-borne disease risks in the United States and around the world. California is just one example of this issue."
Aedes albopictus in California
Along with seven other scientists, Attardo and Onyango co-authored a research article in the Oct. 2nd edition of Frontiers in Microbiology on "Zika Virus Infection Results in Biochemical Changes Associated With RNA Editing, Inflammatory and Antiviral Responses in Aedes albopictus."
Aedes albopictus, also a day-biting mosquito, can transmit Zika and other infectious diseases. "The Zika virus infected more than 1 million people during an epidemic that began in 2015 in Brazil," according to this report, Invasive Mosquito Species Plunge Deeper Into California. The virus also can spread during sex.
Onyango holds two degrees from the University of Nairobi, Kenya: a bachelor of science degree in biochemistry and zoology and a master's degree in applied parasitology. She received her doctorate in veterinary entomology from Deakin University and Australian Animal Health Laboratory, Commonwealth Scientific and Industrial Research Organisation (CSIRO), and then completed postdoctoral training at the Yale School of Public Health, Department of Epidemiology of Microbial Diseases.
Cooperative Extension specialist and assistant professor Ian Grettenberger coordinates the fall seminars. For any technical issues regarding the seminar, contact Grettenberger at firstname.lastname@example.org
She's been making her mark in all three since enrolling in 2016 in the UC Davis Department of Entomology and Nematology's Ph.D. program, with a designated emphasis in the biology of vector-borne diseases.
Winokur, who studies with major advisor Christopher Barker, associate professor, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, is a newly selected fellow of Professors for the Future (PFTF).
This is a program sponsored by UC Davis Graduate Studies “to recognize and develop the leadership skills of outstanding graduate students and postdoctoral scholars who have demonstrated their commitment to professionalism, integrity, and academic service.”
As a fellow, she will receive a stipend of $3000. Traditionally, approximately 12 fellows annually are selected to participate in the yearlong program, launched in 1992.
The PFTF program is designed to prepare UC Davis doctoral students and postdoctoral scholars “for an increasingly competitive marketplace and a rapidly changing university environment,” according to PFTF co-directors Ellen Hartigan-O'Connor, acting associate dean of UC Davis Graduate Studies, and Teresa Dillinger, academic administrator.
During the year, the fellows will receive formal training-in-teaching methods and course design; participate in a seminar course on ethics and professionalism, and meet regularly for roundtable panel discussions to promote their professional development, intellectual growth and leadership skills, the directors said.
The fellows will work on projects of their own design to enhance their graduate or postdoctoral experience and professional development of their colleagues. They summarize their projects in end-of-the-year reports. (See 2019-2020 fellows.)
Winokur titled her successful proposal, “Addressing Financial Barriers to Participation in STEM (Science, Technology, Engineering and Mathematics).”
“Graduate students perform many roles as researchers, mentors, educators, communicators, service leaders, and humans,” wrote Winokur, who is president of the UC Davis Entomology Graduate Student Association. “Financial insecurity affects students' abilities to perform these roles well, and provides a leg up to students with financial support beyond a graduate student stipend. We know that diversity is important in academia; cultivating talent from folks across the social spectrum leads to innovative and appropriate solutions.”
“Addressing financial barriers to participation in STEM graduate programs will lead to more diverse and inclusive programs,” she wrote. “Further, financial insecurity affects those who enters graduate school in the first place; research experience is often required to be considered for acceptance into graduate school, which unfortunately is often offered in the form of unpaid research internships. This can filter out low-income students early, making academia even more elite than it already is.”
Winokur will collaborate with existing resources on campus to set up a series of workshops to address the issues, focusing on three points: (1) creative ways to fund your research (2) how to support your research mentees—why unpaid labor filters low income and other disadvantaged students, and (3) making your teaching cheaper—how to make education more accessible for low-income and other disadvantaged students.
“I've been interested in applying to the Professors for the Future program for a couple years,” she said. “This year, I feel that I am at a good point in my graduate career to develop my skills through the PFTF coursework and to contribute to the graduate student community through a PFTF project.”
Since 2016, the UC Davis doctoral student has developed her teaching, mentoring, course development, and leadership skills through various courses and programs, “which has led to a basic understanding of my teaching philosophy and pedagogy.” She aims to develop her skills to “further align with my core values of diversity, equity, and inclusion in the classroom and laboratory.”
Olivia grew up in Laguna Niguel, Calif. where she focused on science at the Dana Hills High School Health and Medical Occupations Academy. She holds a bachelor's degree, 2015, from Cornell University, where she majored in interdisciplinary studies, focusing on the environmental effects on human health. While at Cornell, she worked as an intern for the National Institutes of Health, working on climate change initiatives for the National Institute of Environmental Health Sciences and the Fogarty International Center.
Winokur is a National Science Foundation Graduate Research Fellowship. She is a two-time recipient of the Bill Hazeltine Memorial Research Award, given annually to an outstanding UC Davis graduate student studying vector-borne diseases.
Winokur, who researches Aedes aegypti mosquitoes, is the co-author of research published in several journals, including PLOS Neglected Tropical Diseases. Her first first-author paper, “Impact of Temperature on the Extrinsic Incubation Period of Zika Virus in Aedes aegypti” was just published in March.
Since 2017, she has served as a volunteer with the California Department of Public Health's Vector-Borne Disease Section, assisting with hantavirus and plague surveillance by rodent trapping and testing.
Winokur mentors undergraduate students in the UC Davis Research Scholars Program in Insect Biology (RSPIB), founded and directed by faculty members Jay Rosenheim, Joanna Chiu and Louie Yang, UC Davis Department of Entomology and Nematology.
Active in STEM projects, Winokur co-founded GOALS (Girls' Outdoor Adventure in Leadership and Science) in 2017, a program that develops and runs free two-week summer science programs for high school girls and gender expansive youth from backgrounds underrepresented in STEM fields. The girls learn science, outdoor skills and leadership hands-on while backpacking in Sequoia National Park./span>
They manage to find us, don't they? Even when we're doing our best to try to avoid them!
It's not so well-known that mosquitoes, both male and female, frequent plants to feed on nectar for energy.
And now UC Davis chemical ecologist Walter Leal and scientists Fangfang Zen and Pingxi Xu of the Leal lab have discovered that the odorant receptors from the southern house mosquito, Culex quinquefasciatus, and the yellow fever mosquito Aedes aegypti, are sensitive to floral compounds.
The manuscript: "Odorant Receptors from Culex quinquefasciatus and Aedes aegypti Sensitive to Floral Compounds."
The team, led by Leal, a distinguished professor in the Department of Molecular and Cellular Biology and a former chair of the UC Davis Department of Entomology, cloned the genes of several odorant receptors from the mosquitoes and tested them, using egg cells of Xenopus toads. They exposed the cloned receptors to different scent chemicals.
"We are delighted to find out how mosquitoes smell plant-derived compounds and are repelled by them," Leal said. "These findings may lead to the discovery of better repellents from natural sources."
"Mosquitoes rely heavily on the olfactory system to find a host for a bloodmeal, plants for a source of energy and suitable sites for oviposition," the scientists explained in their abstract. "Here, we examined a cluster of 8 odorant receptors (ORs), which includes one OR, CquiOR1, previously identified to be sensitive to plant-derived compounds. We cloned 5 ORs from Culex quinquefasciatus and 2 ORs from Aedes aegypti, ie, CquiOR2, CquiOR4, CquiOR5, CquiOR84, CquiOR85, AaegOR14, and AaegOR15 and then deorphanized these receptors using the Xenopus oocyte recording system and a large panel of odorants. 2-Phenylethanol, phenethyl formate, and phenethyl propionate were the best ligands for CquiOR4 somewhat resembling the profile of AaegOR15, which gave the strongest responses to phenethyl propionate, phenethyl formate, and acetophenone. In contrast, the best ligands for CquiOR5 were linalool, PMD, and linalool oxide. CquiOR4 was predominantly expressed in antennae of nonblood fed female mosquitoes, with transcript levels significantly reduced after a blood meal. 2-Phenylethanol showed repellency activity comparable to that of DEET at 1%. RNAi experiments suggest that at least in part 2-phenylethanol-elicited repellency is mediated by CquiOR4 activation."
Meanwhile, Leal is gearing up for the 2019 Entomological Society of America (ESA) meeting in St. Louis, Mo., where he will deliver the Founders' Memorial Award Lecture on “Tom Eisner — An Incorrigible Entomophile and Innovator Par Excellence,” at the awards breakfast on Tuesday, Nov. 19.
ESA officials selected Leal, an ESA fellow and internationally recognized chemical ecologist, for the global honor. Leal is the first UC Davis scientist selected to present the Founders' Memorial Lecture, although medical entomologist Shirley Luckhart of the University of Idaho, formerly of UC Davis, delivered the lecture in 2018.
The 7000-member ESA is the world's largest organization serving the professional and scientific needs of entomologists and people in related disciplines. ESA, founded in 1889, is headquartered in Annapolis, Md.
Lark Coffey, an assistant professor in the Department of Pathology, Microbiology and Immunology, UC Davis School of Veterinary Medicine and a member of the Center for Vectorborne Diseases, will speak on "Zika Virus in Macaques, Mice and Mosquitoes: Contrasting Virulence and Transmissibility in Disparate Hosts."
And her host is medical entomologist and seminar coordinator Geoffrey Attardo, assistant professor in the UC Davis Department of Entomology and Nematology. This is part of the department's series of fall seminars.
Coffey says on her website: "Mosquito-borne viruses like Zika, chikungunya, West Nile, St. Louis encephalitis and dengue virus are expanding to cause more human infections worldwide. Unfortunately, no licensed human vaccines for these viruses are available. Management of disease is therefore restricted to palliative care for infected people and minimizing exposure to mosquitoes. Our research focuses on several central themes with a common goal of reducing the burden of disease caused by arboviruses. These include: understanding viral genetic factors that promote arbovirus outbreaks predicting viral mutations that enhance arbovirus transmissibility by mosquitoes and disease in humans or animals increasing safety of candidate live-attenuated vaccines improving arbovirus surveillance in mosquitoes."
Her abstract of her seminar Nov. 7 is technical. "Fetal microcephaly and death are now recognized as severe forms of congenital Zika syndrome; however, it is still unclear whether recent Zika virus (ZIKV) mutations contribute to this phenotype," Coffey says in her abstract. "We identified a single intrahost variant in the ZIKV NS2B protein (NS2BM1404I) from a rhesus macaque (RM) fetus that died after experimental ZIKV inoculation in the first trimester. Targeted deep sequencing flanking NS2B1404 in subsequent cohorts of RM mothers and their fetuses identified NS2BM1404I at minority frequency and sometimes at consensus levels in 3 additional dead or stillborn RM fetuses and/or the plasma of their mothers and in 2 more RM mother and fetus pairs whose fetuses survived to near term or were born alive. In outbred pregnant mice inoculated subcutaneously, we observed that NS2BI1404 engineered into an infectious clone confers fetal infection while ZIKV-NS2BM1404 does not. By examining sequence data from recent epidemics, we found that NS2BM1404I occurs rarely (5/500, 1%) in consensus human ZIKV genomes.
"We also deep sequenced ZIKV genomes from non-pregnant human adults, infants, and Ae. aegypti from the epidemic and observed that NS2BI1404 was more often present at intra-host levels in humans compared to mosquitoes," she continues in her abstract. "Since the primary ZIKV transmission cycle is human-mosquito-human, viral mutations that arise in one host must be maintained in the alternate host to be perpetuated. We therefore hypothesized that ZIKV NS2BM1404Imay not be efficiently transmitted by Aedes aegypti mosquitoes, explaining its low frequency in humans during outbreaks. Using infectious clone-derived ZIKV, we examined vector competence in Ae. aegypti from Puerto Rico. Although infection and dissemination rates were not different, we found that Ae. aegypti did not transmit ZIKV-NS2BI1404 as efficiently compared to ZIKV-NS2BM1404 5 [7/20 (35%) versus 10/20 (50%), p>0.05] and 7 [3/20 (15%) versus 13/20 (65%), P<0.001, Chi-squared] days post-feed. The poor transmissibility of this potentially vertebrate adaptive ZIKV mutation may explain its low frequency in febrile humans. This data highlights the evolutionary complexity during arbovirus transmission cycles and suggests that some pathogenic viral mutations are not likely to spread in epidemics."
Coffey received her bachelor of science degree in biology from the University of the South, Sewanee, Tenn., in 2000, and her doctorate in experimental pathology at the University of Texas Medical Branch, Galveston, Texas in 2005.
Thanks to the generosity of his family, his work is continuing through memorial research grants to outstanding graduate students at the University of California, Davis.
Hazeltine, a native of San Jose, was a U.S. Navy veteran who studied entomology at UC Berkeley and received his doctorate in entomology from Purdue University in 1962. He managed the Butte County Mosquito Abatement District, Oroville, from 1966 to 1992, and the Lake County Mosquito Abatement District from 1961-1964.
He was an ardent supporter of the judicious use of public health pesticides to protect public health, remembers Bruce Eldridge, emeritus professor of entomology at UC Davis and former director of the (now folded) statewide UC Mosquito Research Program. Eldridge eulogized him at the 2005 annual meeting of the American Mosquito Control Association (AMCA) as "a man who made a difference." The AMCA journal published his eulogy in its 2006 edition. (See http://entomology.ucdavis.edu/files/154217.pdf)
"Bill was a medical entomologist who had a varied career in the field of mosquito biology and control, but he will forever be remembered as a man who fought in the trenches of the pesticide controversy from 1960 until the end of his life, and who made the safe and efficient use of pesticides in public health a personal crusade," Eldridge said.
In his memory, his three sons--Craig Hazeltine of Scottsdale, Ariz., Lee Hazeltine of Lincoln, formerly of Woodland, and the late Jeff Hazeltine (1958-2013)—established the UC Davis Bill Hazeltine Graduate Student Research Awards in 1997. Each year they travel to Davis to honor the recipients at a luncheon, timed with their attendance at a scholarship and fellowship celebration, hosted by Dean Helene Dillard, UC Davis College of Agricultural and Environmental Science.
The 2017 recipients are
- Olivia Winokur of the Christopher Barker lab, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine. Her funded project ($2425): “Identifying Aedes Mosquito Eggs Using Hyperspectral Imaging: a Rapid, Low-Cost, Non-Destructive Method to Improve Mosquito Surveillance and Control.”
- Maribel "Mimi" Portilla of the Sharon Lawler lab, UC Davis Department of Entomology and Nematology. Her funded project ($2032): “The Management of Invasive Weeds and their Effects on Larval Culex mosquitoes."
Winokur is also the newly announced 2018 recipient of $3,094 to investigate Aedes aegypti immune response to Zika virus. (Portilla expects to receive her doctorate in six to 12 months.)
“Aedes aegypti and Aedes albopictus are mosquitoes capable of transmitting dengue, chikungunya, yellow fever, and Zika viruses,” Olivia Winokur explained in her 2017 application. “These species are invasive and present in California and continue to spread, increasing the likelihood of local transmission of these devastating viruses. Additionally, Aedes notoscriptus, an Australian mosquito whose vector competence for many viruses is unknown, has been detected in Los Angeles and is likely to spread in the state. Aedesmosquitoes are readily detected using ovitraps, a cheap and effective sampling method to detect the presence of gravid females. Ovitraps are especially useful when mosquito populations are low as traps for adult Aedes are unreliable. Once collected, the eggs cannot be differentiated using a stereomicroscope. Traditionally, identifying Aedes eggs collected in ovitraps requires hatching and rearing to adult for visual identification, which is time consuming and leads to a time lag for control, potentially allowing invasive species to spread without intervention.”
“Currently, I am developing a non-destructive, low-cost method to rapidly identify Aedes eggs,” Winokur wrote. “I have shown that species-specific surface morphologies of the exochorion can be used to differentiate species using electron microscopy. This method is expensive and therefore not a realistic surveillance technique. We can, however, exploit these species-specific surface morphologies in another way to identify Aedeseggs. Slight changes in morphological characteristics can be captured with high spatial resolution proximal sensing imaging, termed hyperspectral imaging.”
Winokur is testing “the use of hyperspectral imaging to differentiate between eggs collected from lab colonies of native and invasive Aedes mosquitoes in California. Preliminary data indicate this method shows promise for identifying species and warrants further testing. Once I have created species-specific reflectance profiles and validated my identification method using colony eggs, I will collect field eggs and validate the identification method using these field eggs.” She is working with hyperspectral imaging expert Christian Nansen, agricultural entomologist and assistant professor, UC Davis Department of Entomology and Nematology, on the project.
Winokur describes hyperspectral imaging as “a powerful tool that recognizes slight changes; therefore, we need to ensure that all samples are collected and conditioned the same way before testing. Samples must be imaged directly on the oviposition paper because exochorion cells are damaged by the ‘glue' the female uses to attach her eggs to the substrate; imaging removed eggs leads to inconsistent reflectance profiles. This method for rapidly identifying Aedes eggs will allow for quick response to the detection of invasive Aedes mosquitoes.”
After finishing her Ph.D., Winokur plans to remain in academia, but “I'm unsure exactly what that will look like! I really enjoy research, teaching, and mentoring so I'd like to have a career where I can do all of these. I also plan to have a career where I can conduct translational research with broad global health implications, engage non-scientists, create tools to help decision makers mitigate vector-borne disease burden worldwide, and encourage interest and diversity in STEM (science, technology, engineering and mathematics).”
Maribel "Mimi' Portilla
“At UC Berkeley School of Public Health, I was able to study health and disease within a larger context, and learned to consider the biological and the social determinants of disease. As I completed my degree, I realized I really missed the research experiences I had as an undergraduate. So, I looked for a way to bridge my new-found passion for public health and basic science research. This led me to UC Davis, where I learned about One Health and am now pursuing a Ph.D in medical entomology. Medical entomology is a perfect example of a One Health field, where I can seek out how interactions between humans and animals impact health. I am particularly interested in researching how disease risk may change as people manipulate the environment."
Her academic life revolves around writing her dissertation; teaching UC Davis classes (she's taught entomology, general biology and One Health classes); research; and public outreach. Since 2012, she has mentored some 30 undergraduate students on developing and executing their research experiments. She praised the “the diversity of my interns; they each brought such important and unique perspectives to the project.”
What are her career plans?
“Due to my diverse interests and skill set, I am very open about my career choices," Portilla said. "I have extensive teaching experience, and would love to be a professor with both teaching and research opportunities. However, there are many opportunities beyond academia. My research is introducing me to many other ways in which my work and research can help keep people safe and healthy. I hope to develop a strong research skill set while at UC Davis, and find a career path which takes advantage of my diverse abilities and love for One Health and Public Health."
Portilla mentioned pursuing a career as a teacher in a small liberal arts school to teach public health, general biology and global diseases classes, as well as do outreach and research. “I'm more of a scientist than an entomologist,” she said.
She may also pursue a career working in vector-control health education at the county, district or state level. “I'm open at this point,” Portilla said. Overall, she is geared toward improving public health outcomes through healthier environments. “I care about how outcomes affect the larger population,” she said.
Meanwhile, it's good to see that William Emery Hazeltine's passion for medical entomology lives on, and to see UC Davis graduate students benefit, all thanks to the generosity and thoughtfulness of the Hazeltine family. The "family" of 42 recipients since 1997 includes Christopher Barker, Winokur's major professor, who received a Hazeltine research award in 2006.
The complete list of recipients:
- 2018: Olivia Winokur (newly announced)
- 2017: Maribel "Mimi" Portilla and Olivia Winokur
- 2016: Sandy Olkowski, Maribel “Mimi” Portilla and Stephanie Kurniawan
- 2015: Sandy Olkowski, Maribel “Mimi” Portilla and Stephanie Kurniawan
- 2014: Martha Armijos, Elizabeth “Lizzy” Glennon and Rosanna Kwok
- 2013: Jenny Carlson, Elizabeth “Lizzy” Glennon and Sandy Olkowski
- 2012: Jenny Carlson, Kelly Liebman and Sandy Olkowski
- 2011: Brittany Nelms Mills, Kelly Liebman and Jenny Carlson
- 2010: Tara Thiemann and Jenny Carlson
- 2009: Kelly Liebman and Wei Xu
- 2008: Ashley Horton and Tara Thiemann
- 2007: Lisa Reimer and Jacklyn Wong
- 2006: Christopher Barker and Tania Morgan
- 2005: Nicole Mans
- 2004: Sharon Minnick
- 2003: Hannah Burrack
- 2002: Holly Ganz and Andradi Villalobos
- 2001: Laura Goddard and Linda Styer
- 2000: Laura Goddard
- 1999: Linda Boose Styer
- 1998: Larisa Vredevoe
- 1997: John Gimnig