- Author: Kathy Keatley Garvey
Male Aedes aegypti mosquitoes infected with a bacterium, Wolbachia pipientis, are being released in Clovis, Fresno County, where this mosquito was discovered in June 2013. Although this mosquito is now found in California, there has been no locally transmitted case of the Zika virus in the state.
The project, to determine dispersal and survival, began Monday, May 10.
“The daytime-biting mosquito, which feeds predominantly on humans, has spread to at least seven counties since its discovery in Clovis,” said Cornel, a mosquito researcher and faculty member with the UC Davis Department of Entomology and Nematology and the UC Kearney Agricultural Research and Extension Center, Parlier.
“The biting nuisance and potential of the mosquito Aedes aegypti to transmit Zika, Chikungunya and dengue viruses in California is cause for concern,” he said. “Efforts to curb its spread and reduce populations have not been very effective. Control efforts have included educating the public to remove standing water (source reduction) insecticide barrier sprays and bacterial larviciding.”
The collaborative effort involves Steve Mulligan, director of the Consolidated Mosquito Abatement District, based in Fresno County; Stephen Dobson of the University of Kentucky; MosquitoMate Inc, (mosquitomate.com); and UC Davis. The researchers will evaluate the population suppressive ability of the novel sterile insect technique, which is part of a comprehensive vector management approach.
Only Aedes aegypti is targeted. “When the Wolbachia-infected male mosquito mates with non-infected females, the result is “cytoplasmic incompatibility, which causes the female to lay infertile eggs that will not hatch,” Cornel explained.
“This approach requires the release of tens of thousands of Wolbachia-infected males into residential neighborhoods where this mosquito is a nuisance,” the medical entomologist said. “Releasing large numbers of males increases the chance that an introduced male will mate with the native females.”
Although residents will notice increased numbers of male mosquitoes, male mosquitoes do not bite and cannot transmit disease. Both U.S,federal and State regulatory agencies have approved the technique for evaluation of effectiveness.
“This sterile insect technique was evaluated in 2015 in Los Angeles to suppress another invasive mosquito, Aedes albopictus,” Cornel said, adding that the results from that trial look promising.
The Zika virus, now spreading throughout the Western hemisphere, was first identified in Uganda in 1947 in rhesus monkeys, according to the World Health Organization. It was subsequently identified in humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific.
Despite the mosquito's invasion into new areas of the United States, there are no reported cases of locally transmitted Zika virus in California or in the contiguous United States, according to the Centers for Disease Control and Prevention. The cases have all involved travelers returning home from countries plagued with disease outbreaks.
“We can't predict how far this mosquito will spread in California,” said Cornel, noting that its range has expanded “south of Fresno to San Diego. The farthest site north is Madera in the Central Valley, but it's also been found in the more coastal area of Menlo Park in San Mateo.”
It's troubling that the mosquito is becoming more and more resistant to pesticides, said Cornel, who collects, rears and researches mosquitoes from all over the world, including the United States, Mali, Cameroon, Comoros, Tanzania, South Africa and Brazil.
“We have found that Aedes aegypti have insecticide resistance genes which likely explains why the use of ultra-low volume and barrier spray applications for control have not worked as well as expected.”
- Author: Kathy Keatley Garvey
The lecture, to take place at 10:45 a.m. in the Alpha Gamma Rho (AGR) Hall, is sponsored by the College of Agricultural and Environmental Sciences and the Storer Life Sciences Endowment of UC Davis.
At Penn State, Thomas serves as the Huck Scholar in Ecological Entomology and directs the Ecology Institute, in addition to his duties as a professor of entomology in the Department of Entomology and Centre for Infectious Disease Dynamics.
He will be introduced by Professor Shirley Luckhart of the UC Davis Department of Medical Microbiology and Immunology, coordinator of the event.
Thomas researches many aspects of the ecology and evolution of insect pests and diseases in his drive to understand the consequences of global change and to improve the effectiveness and sustainability of pest and disease management. His work involves predicting and understanding the impact of invasive species, and researching biodiversity and ecosystem health, plus many aspects of biological control.
Last December Thomas and his research team at Penn State, in collaboration with partners in Europe and Africa, received a five-year, $10.2 million grant from the Bill and Melinda Gates Foundation to investigate a new method for preventing the transmission of malaria.
“The method involves limiting mosquito access to houses by blocking openings and installing ‘eave tubes' that contain a unique type of insecticide-laced mosquito netting developed by Dutch partner In2Care that kills the insects as they attempt to enter,” according to a Penn State news release.
Thomas was quoted as saying: “Nearly half of the world's population is at risk of contracting malaria, and according to the most recent World Health Organization report, an estimated 438,000 people died from the disease in 2015. The use of insecticides to control mosquitoes has saved millions of lives, but this tactic is increasingly challenged because mosquitoes quickly evolve resistance to the very limited number of insecticides currently used in public health. The eave tube approach presents a novel strategy to help combat this challenge by simultaneously making houses more mosquito proof and providing a novel way of delivering insecticides, which creates opportunities for using a wider range of insecticidal products."
"The small amount of insecticide used in the tubes means that it is cheap to treat an entire house," said Thomas. "Furthermore, retreatment is easy, as it requires simple replacement of small pieces of netting within the tubes."
Internationally recognized, Thomas is a recipient of the Commonwealth Scientific and Industrial Research Organization (CSIRO) Medal for Research Achievement, is a fellow of the American Association for the Advancement of Science, and an honorary professor at the University of Witwsatersand, South Africa. He also received Penn State's Alex and Jessie Black Award for Research Excellence.
- Author: Kathy Keatley Garvey
The AMCA, founded in 1935, is a scientific and educational public service organization. Its mission is “to provide leadership, information, and education leading to the enhancement of health and quality of life through the suppression of mosquitoes and other vector-transmitted diseases, and the reduction of annoyance levels caused by mosquitoes and other vectors and pests of public health importance.”
The plaque reads: “In recognition of outstanding service to the AMCA and for contributions to the science of mosquito ecology and bionomics and to the epidemiology and control of arboviruses."
Working closely with the Mosquito and Vector Control Association of California and the California Department of Public Health, he was instrumental in molding the California arbovirus surveillance diagnostics, data management and reporting statewide into an effective decision support system for intervention.
Reisen accepted the award on behalf of his collaborators, colleagues and staff at UC Berkeley and UC Davis, and acknowledged “the important impact that the Mosquito and Vector Control Association of California and the California Department of Public Health has had on our program's success.”
Reisen, who retired from UC Davis in 2014 from some of his responsibilities, is a professor emeritus with the Department of Pathology, Microbiology and Immunology (PMI), School of Veterinary Medicine, and a former director of the Center for Vectorborne Diseases. He continues to serve as editor-in-chief of the Journal of Medical Entomology, published by Entomological Society of America. He has served as a graduate student advisor for the UC Davis Department of Entomology and Nematology as well as the Epidemiology Graduate Group.
Reisen earlier received the 2015 Meritorious Service Award from the Mosquito and Vector Control Association of California (MVCAC). He has published more than 300 peer-reviewed publications and book chapters in the field of medical entomology.
Throughout his career, he directed collaborative projects ranging from field evaluations of genetically modified mosquitoes to aerial applications of insecticides, the vector competence of mosquitoes for endemic and newly introduced viruses, established new molecular surveillance testing paradigms for arboviruses, and initiated interactive networks for sharing surveillance data with mosquito control agencies and public health officials to speed mosquito control response times and to minimize disease risk to humans, according to Craig Downs, general manager of the Contra Costa MVCAC District.
“Several examples of his continual scientific contributions include: the effects of climate variation on arthropod-borne pathogen transmission, modeling efforts for predicting arbovirus risk, the application of insecticides for reducing the disease burden of West Nile virus in California, the use of liquid suspension array technologies for the identification of mosquito blood meals and his keen observation of the role of stagnant swimming pools as breeding sites for Culex spp. vectors in Kern County,” Downs said.
Reisen's medical entomology career includes the U.S. Air Force, University of Maryland School of Medicine, UC Berkeley School of Public Health and the Center for Vectorborne Diseases at UC Davis School of Veterinary Medicine. He directed the Arbovirus Field Station in Bakersfield from 1980-2013 and the Center for Vectorborne Diseases, based at UC Davis, from 2009 to 2014.
In recognition of his contributions to research, service and graduate training, he was awarded Lifetime Award for Achievement in Medical Entomology and the Distinguished Service Award by the Society for Vector Ecology; Fellow, Entomological Society of America; Academic Federation Award for Excellence in Research, University of California, Davis; John N. Belkin Award for Excellence in Vector Ecology, American Mosquito Control Association; and the Harry Hoogstraal Medal, American Society of Tropical Medicine and Hygiene.
Thomas Scott, emeritus professor of entomology at UC Davis and known for his work on the yellow-fever or dengue mosquito, described Reisen as “an international leader in mosquito ecology and arbovirus epidemiology. His contributions to his field of study are stunning. His prolific, detailed field and laboratory studies have reshaped the way we think about mosquito-borne pathogen transmission dynamics. He has greatly improved disease prevention programs.”
A native of New Jersey, Reisen holds a doctorate in zoology (1974) from the University of Oklahoma, Norman, with a focus on medical microbiology and ecology.
- Author: Kathy Keatley Garvey
“It's an issue of great concern, especially as current control methods do not appear to be working well,” said Cornel, who does research on the mosquito in Clovis, Fresno County, where it was discovered in June 2013. Simultaneously, the insect was found in the cities of Madera and San Mateo.
“This ongoing widespread invasion and establishment proves that this is no longer a regional issue and has affected many cities and towns in California,” he wrote Feb. 8 in F1000 Research, http://f1000research.com/slides/5-149.
But Cornel is optimistic that the pest management intervention strategies and surveillance and control tactics now underway will help control its spread. Infected Aedes aegypti can transmit dengue, yellow fever, Zika and chikungunya viruses.
The Zika virus, now spreading throughout the Western hemisphere, is an emerging mosquito-borne virus that was first identified in Uganda in 1947 in rhesus monkeys, according to the World Health Organization. It was subsequently identified in humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific.
Despite the mosquito's invasion in parts of the United States, there are no reported cases of locally transmitted Zika virus in California or in the contiguous United States, according to the Centers for Disease Control and Prevention. The cases have all involved travelers returning home from countries plagued with disease outbreaks.
Cornel works with the Consolidated Mosquito Abatement District, based in Fresno County, to tackle the spread of the mosquito there. The district covers 1,058 square miles, including part of Kings County.
How far north in California will the mosquito, commonly known as yellow fever mosquito, spread?
“I don't want to exclude the possibility that it may spread as far north as Sacramento,” said Cornel, who collects, rears and researches mosquitoes from all over the world, including the United States, Mali, Cameroon, Comoros, Tanzania, South Africa and Brazil. “We need to see if it overwinters as eggs or adults or both.”
It's troubling that the mosquito is becoming more and more resistant to pesticides, Cornel said. “We have found that the Aedes aegypti have insecticide resistance genes which likely explains why their ultra-low volume and barrier spray applications have not worked as well as expected.”
At Clovis, Cornel and his colleagues trap mosquitoes in gravid or ovitraps; study overwintering and flight dispersal; and employ mark-release-capture trials to estimate dispersal and population size, needed to plan biological (Wolbachia) and chemical auto-dissemination control strategies. They also engage in “recruiting” mosquitoes to kill other mosquitoes. “We have mosquitoes spread insecticides for us, that is, we turn them into mosquito-control workers through the use of insect growth regulators and biopesticides.”
Their 27-slide document, “Surveillance and Control of Aedes aegypti Mosquito in Clovis, Calif.,” published in F1000 Research details their research with text and maps. It is work of Cornel and Yoosook Lee of UC Davis; Stephen Dobson of the University of Kentucky; Corey Bansfield of MosqMate Inc. and Jodi Holeman, Mark Amireno, Charles Smith and Stephen Mulligan III of the Consolidated Mosquito Control District. In the document, Mulligan, director of the Consolidated Mosquito Control District, describes Aedes aegypti as “the rat of the mosquitoes.”
The California team works with University of Kentucky scientists to develop novel control strategies. One trial involves coating male mosquitoes with insect growth regulators, which are passed on to the females. Males are also infested with a biopesticide or “a good bacteria-like organism,” Wolbachia. “The male transfers it to the female, which affects the ovaries and negatively affects immature development,” Cornel explained. “It's not new, but it's not been employed in large trials.”
Regarding flight dispersal, Cornel has found that “males can fly well over 200 meters in one night from their breeding site. We previously thought it was no more than 60 to 100 meters.”
“The Aedes aegypti fly predominantly during cooler periods of the day,” the medical entomologist said. “When it's too hot, they hang around the shade.” When residents walk at dusk, both male and female mosquitoes can follow them. “Only the females bite but the males will hang around your ankle waiting for the females to arrive.”
The researchers target mosquito breeding sites, primarily yard drains. “Despite the drought and the elimination of visible bodies of water, such as bird baths, pet bowls and flower pots, there's a major issue: yard drains,” Cornel said. “Yard drains installed in new home developments empty into the gutter or street and are cryptic breeding sites for mosquitoes.” He speculates that these mosquitoes are breeding underground.
“These drains are not easily accessible and we can't see the mosquitoes,” Cornel pointed out. “We need to blow out the water and plug these yard drains to eliminate these breeding sites.” He suggests that cities everywhere address this public safety issue and “redesign the yard drains.”
Cornel works with the Consolidated Mosquito Abatement District in setting gravid or “killing traps” in the front yards of homes in Clovis. The traps, which look like five-gallon buckets, contain orchard grass and water. “When the orchard grass decomposes, it releases a plume of chemicals that attracts female Aedes aegypti to lay their eggs in,” Cornel said. A screen prevents them from reaching the water to lay their eggs. The insects adhere to black sticky paper.
It's crucial for the public to become involved, Cornel said. “We have to focus on public education. We have to get the message across to eliminate mosquito breeding sites. We can't go to every house. We must rely on the public to eliminate the breeding sites.”
It's possible—but he hopes not—that what is now a “mosquito nuisance” will result in a disease outbreak.
Related Links:
- Anthony Cornel: Mosquito Man UC Davis Department of Entomology and Nematology
- Anthony Cornel, Kearney Agricultural Research and Extension Center
- Yoosook Lee, UC Davis Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine
- F1000 Research
- Traps Tested in Clovis (UC ANR)
- Aedes aegypti, California Department of Public Health, Aedes aegypti
- Consolidated Mosquito Control District, based in Fresno County
- Author: Kathy Keatley Garvey
Internationally known for his mosquito research and publications spanning more than four decades, Bill Reisen officially retired in July from the University of California, Davis, but mosquitoes shouldn't breathe a collective sigh of relief and go about their blood-sucking business.
Reisen, now a professor emeritus with the Department of Pathology, Microbiology and Immunology (PMI), School of Veterinary Medicine, vows to continue his mosquito research; manage the vector-borne disease surveillance diagnostics lab; advise graduate students in the School of Veterinary Medicine; mentor several new PMI faculty members; direct the Center for Vectorborne Diseases (CVEC) and edit the Journal of Medical Entomology. In between, he and his wife Norma will travel throughout the United States and Europe and to their mango farm in the Philippines.
And along the way, he'll probably encounter the 10 species mosquitoes that he developed a close and personal relationship with--“skeeters” that transmit diseases such as malaria, yellow fever, encephalitis and West Nile virus.
While other people count sheep to go to sleep, Reisen probably counts mosquitoes at his current or former research sites:
Pakistan? Culex tritaeniorhynchus, Anopheles stephensi and Anopheles culicifacies
Nepal? Anopheles fluviatilis and Anopheles maculatus
California? Culex tarsalis, Culex pipiens complex, Culex stigmatosoma, Aedes dorsalis and Aedes melanimon
Meanwhile, the accolades flow.
“And,” Scott added, “he is a genuinely good person. For those of us fortunate enough to have worked with him, Bill is recognized for the exceptional rigor of his science and uniquely high quality of his character."
Colleague Bruce Eldridge, emeritus professor of entomology at UC Davis, described Reisen as “the hardest working and most dedicated entomologist I have ever had the pleasure of working with. Nearly everything he does has a definite purpose, and the results of his research have improved substantially our ability to protect people from vectorborne diseases both here in California and elsewhere in the world.”
“He has also instilled these principles of hard work and concentration on important subjects to study in a long list of graduate students, post-doctoral researchers, and other visiting scientists. People go to Bill all the time for advice and other kinds of help. He never says no. He is a remarkable individual, and I know he won't quit doing the things he does just because he is retiring.”
A native of New Jersey, Reisen holds a doctorate in zoology (1974) from the University of Oklahoma, Norman, with a focus on medical microbiology and ecology.
Young Bill began his academic career as an undergraduate in entomology at the University of Delaware in 1963 and as a research assistant with Clemson University in 1967, monitoring organochloride insecticide residues in fish and aquatic insects. As a teaching assistant at Clemson, he taught animal ecology in 1968 and continued his research on stream ecology and fish-feeding behavior.
Reisen served as a captain in the U.S. Air Force from 1969 to 1971. He was assigned to the 5th Epidemiological Flight, Manila and 1st Medical Service Wing, Clark Air Base, Republic of the Philippines. His duties included vector-borne disease surveillance and control programs on USAF Bases in Pacific Air Command, which took him on temporary duty to Japan, Taiwan, Korea, Okinawa, Thailand, Guam and Hawaii.
Reisen resumed his academic career from 1971 to 1974 when he taught entomology, zoology, ecology and parasitology courses as a teaching assistant at the University of Oklahoma. He then worked as a research associate from 1974 to 1975 at the University of Maryland School of Medicine, where he did research on a malaria mosquito, Anopheles stephensi, and assisted David Clyde during the first malaria vaccine trials in humans.
In 1975 Reisen was assigned to the University of Maryland School of Medicine's Pakistan Medical Research Center in Lahore, Pakistan, where he served as an assistant professor of international medicine from 1975 to 1980 and headed the Ecology Department. His research involved population ecology and the bionomics of Pakistani mosquitoes and their relation to pathogen transmission and field trials related to genetic control of mosquitoes.
Reisen moved to California in 1980 to become research entomologist and director of the Arbovirus Field Station of the UC Berkeley School of Public Health in Bakersfield. “I worked on population ecology, bionomics, genetics and vector competence of Culex tarsalis in relation to arbovirus ecology and control in California until 1995,” he said. The program later transferred to the UC Davis School of Veterinary Medicine in 1996 and CVEC was born.
“My career can be divided into three phases: (1) education/learning, (2) field research and (3) advising and mentoring,” Reisen said. “Graduate training at Clemson and Oklahoma and my U.S. Air Force assignments in southeast Asia and my position in Pakistan provided a great introduction to how to do field studies and work in remote areas with minimal equipment and support. This training was applied during the 25 years in Bakersfield where we did everything from genetic control trials to host and vector competence studies with several arboviruses.”
“This training and work experience managing integrated field research programs gave me insight on how to mentor graduate students and new faculty, the final phase of my career,” Reisen noted. “The latter experience expanded our research breadth and improved our program immeasurably as I got to know some very bright and engaging students. Throughout my career I was very fortunate to be supported by excellent laboratory and field staff which formed the cornerstone of our NIH-funded research programs.”
Highly honored by his peers, Reisen has received national and international honors that include:
- Lifetime Award for Achievement in Medical Entomology, Society for Vector Ecology, presented at the International Congress, 2001.
- Fellow, Entomological Society of America, 2003.
- Academic Federation Award for Excellence in Research, UC Davis, 2004.
- John N. Belkin Award for Excellence in Vector Ecology, American Mosquito Control Association, 2006
- Distinguished Service Award, Society for Vector Ecology, 2006
- Harry Hoogstraal Medal, American Society of Tropical Medicine and Hygiene, 2012
Reisen's work includes 297 peer-reviewed research publications, plus book chapters.
Since 1984, Reisen has guided seven Ph.D. and postdoctoral students: Mark Eberle, UC Berkeley School of Public Health, and Carrie Nielsen, Christopher Barker, Jennifer Kwan, Gabriella Worwa, Tara Thiemann and Sarah Wheeler, UC Davis. He currently serves as the major professor for two graduate students in Comparative Pathology: Veronica Armijos[rev1] , also manager of the Thomas Scott lab in the Department of Entomology and Nematology, and Andra Hutton.
Chris Barker, now an assistant adjunct professor with PMI and CVEC, said that Reisen is “known to virtually everyone who has spent much time studying mosquitoes or the viruses they transmit.”
“Bill has had a very productive and well-documented career represented in his 297 peer-reviewed scientific papers,” Barker said. “His lasting enthusiasm for his work, good humor, and uncommon humility have been an inspiration to all of his colleagues, especially the students and staff who have had the good fortune to be a part of his research program. One unique aspect of Bill's career is that he spent over 30 years in the field and at the lab bench in contact with mosquitoes almost daily, which is increasingly rare in today's world of digital data collection. It is safe to say that Bill will not quit upon retirement, and his intellectual input and wealth of experience will continue to be valued for years to come.”
Sarah Wheeler participated in the “West Nile virus period” of Reisen's career-- first as a technician, then as a PhD student, and finally, as a post-doctoral scholar. “During the West Nile period Bill facilitated and conducted a body of work leading to the understanding of West Nile virus transmission and overwintering in California. Bill's dedication to the field of arbovirology and fierce work ethic inspired me to follow in his footsteps, and along the way he shaped my approach to science through his lead by example style. Bill has been a fabulous mentor and I am unendingly grateful I took his original job offer that sent me out into the middle of nowhere, but opened upon the world of arbovirology.”
Said Reisen: “Although we did spend a lot of time collecting mosquitoes, we also had a large bird program where we collected, bled and tested more than 85,000 wild bird sera for arbovirus infection and did a host of experimental infection studies with birds ranging from house finch nestlings to adult mallard ducks and black-crowned night herons.”
Robert Washino, emeritus professor and former chair of the UC Davis Department of Entomology and a former administrator with the UC Davis College of Agricultural and Environmental Sciences, lauded Reisen's career.
“Bill has had a very colorful career in medical entomology,” said Washino. He remembers visiting his laboratory at the School of Medicine, Lahore, Pakistan “in another lifetime.”
“Bill's work on several important malaria anopheline vectors in that country constituted important contributions and also included studies on Culex tritaeniorhynchus, the vector of Japanese Encephalitis virus, somewhat comparable to Culex tarsalis, the vector of several arboviruses in the western U.S.,” Washino said.
“Bill will forever be remembered as the continuing lead investigator of the important W. C. Reeves, UC Berkeley arbovirus program in California,” Washino said. He praised Reisen's collaborative work with the California Department of Public Health and local regulatory agencies of the Mosquito and Vector Control Association of California.
As for Bill Reisen, “the retiree,” he says he's looking forward to continuing his myriad of mosquito-related activities “to finish up my career and help protect the health of the citizens of California.”
“My final objective,” he said, in typical Reisen humor, “is to learn to play bogey golf.”