Posts Tagged: mosquitoes
When he was doing research in Brazil in September, he draped a snake around his neck and posed for the camera.
His favorite research subjects, though, are mosquitoes.
- The yellow fever mosquito, Aedes aegypti, found throughout the tropics and subtropics and a newly invasive species in central California.
- The West Nile virus mosquito, Culex quinquefasciatus, found throughout much of the world.
- The malaria mosquito, Anopheles gambiae, which wreaks worldwide havoc.
Cornel's name appeared in the news this week when the UC Davis lab of Walter Leal announced that it had found the odorant receptor that repels DEET in the southern house mosquito, Culex quinquefasciatus mosquito. Cornel provided the mosquitoes that allowed the Leal lab to duplicate his colony. Proceedings of the National Academy of Sciences (PNAS) published the work Oct. 27.
Cornel's main research keys in on the population genetics and ecology of West Nile virus vectors in the United States and population genetics and ecology of major malaria vectors in Africa.
“Anton is a great asset to our program, a wonderful colleague, and a nice team player,” said Leal, a professor in the Department of Molecular and Cellular Biology. “We benefit greatly from his generosity by sharing not only mosquito colonies, but also his encyclopedic knowledge on mosquito biology and ecology. We shared co-authorship in a number of publications, and many more are coming.”
Cornel collaborates with Leal on oviposition attraction in Culex quinquefasciatus and “we are now endeavoring to come up with effective oviposition attractive chemical lures to use in virus surveillance and kill traps.”
“The invasion of Aedes aegypti into central California has been of great concern especially as current control methods do not appear to be working very well,” said Cornel, who works closely with state's mosquito abatement personnel. “We have found that the Aedes aegypti have insecticide resistance genes which likely explains why their ultra-low volume (ULV) and barrier spray applications have not worked as well as expected. Work will be ongoing next year when the Aedes aegypti become active again after a brief slow overwintering period from November to March.”
A native of South Africa, Cornel received his doctorate in entomology, focusing on mosquito systematics, in 1993 from the University of the Witwatersrand, Johannesburg. He completed a post-doctoral fellowship with the Entomology Branch of the Centers for Disease Control and Prevention (CDC), Atlanta, before joining UC Davis in 1997 as an assistant professor and researcher.
How did he get involved in mosquitoes? “My interest in mosquito research started in the mid-1980s when I agreed to conduct a masters study under the guidance of Dr. Peter Jupp at the National Institute of Virology who researched West Nile and Sindbis viruses transmitted by mosquitoes in South Africa,” Cornel recalled. “Thereafter I continued to work on mosquitoes as a scientist employed at the South African Institute for Medical Research before moving to the USA.”
“Who would have thought that that the expertise that I gained on West Nile virus as a master student in South Africa would be used many years later after West Nile virus invaded and spread throughout the USA?”
For more than two decades, Cornel has teamed with fellow medical entomologist and “blood brother” Professor Gregory Lanzaro of the UC Davis School of Veterinary Medicine to study malaria mosquitoes in the West African country of Mali. Their work is starting to show significant results.
“Because of our commitment to conduct long term longitudinal studies and not static investigations,” Cornel said, “we have now shown that considerable selective processes are taking place causing spatiotemporal dynamics of gene flow and fitness events in major malaria vectors M (now Anopheles coluzzii) and S (now Anopheles gambiae) and M/S hybrids in West Africa.”
“We are currently establishing further evidence of the important role of insecticide resistance traits in spatiotemporal dynamics of Anopheles coluzzii, Anopheles gambiae and the Bamako form.” Cornel noted that these results have “considerably important implications in future efficacies of insecticide treated bednets to control indoor biting malaria vectors in West Africa.”
Cornel also teams with Lanzaro and Professor Heather Ferguson of the University of Glasgow to examine the ecology and associated genetics of the major malaria vector Anopheles arabiensis in Tanzania. They began working on the project four years ago.
One of his newest projects is the study of population/genetics, insecticide resistance and cytogenetics in the major malaria vector in Brazil. Cornel and Lanzaro launched their study in September when they traveled to Brazil to begin targeting the culprit, Anopheles darlingi, a “widely distributed species that has adapted to survive in multiple ecological zones and we suspect that it may consist of multiple incipient or closely related species,” Cornel said.
“While in Brazil I collected larvae and dissected salivary glands from them to examine their polytene chromosome inversion structure and polymorphisms,” Cornel related. “Inversions are vitally important to consider in genetic analyses and it takes considerable patience to interpret the chromosomes.”
Cornel and Lanzaro collaborate with Professor Paulo Pimenta of the Laboratory of Medical Entomology, René Rachou Research Centre- FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil. The UC Davis medical entomologists hope to produce good preliminary data from their research trip to write grants and establish a long-term project in Brazil.
Cornel also studies avian malaria. That interest sparked four years ago when he began working in Cameroon with scientists from UCLA and San Francisco State University (SFSU), including SFSU's Ravinger Sehgal, who studies avian blood parasites. Cornel's graduate student Jenny Carlson, in her final year of her Ph.D studies at UC Davis, is investigating avian malaria in Fresno County.
The Cornel-Carlson research implicates that considerable fidelity exists between Culex mosquito species and species of plasmodium they transmit. “This is contrary to the currently held belief that all Culex mosquitoes are equally capable of transmitting avian malaria,” Cornel said. “In our investigations, we described a new species of avian malaria which is very common in songbirds in Fresno County (published in Parasitology Research).”
Cornel plans to continue working with Sehgal investigating the effects of deforestation on transmission of avian parasites in Cameroon. They recently submitted a National Science Foundation grant proposal. “A large swath of primary forest is slated to be deforested in Cameroon and replaced with Palm oil plantations and we will investigate the effects of this hopefully, as it happens.”
Also new on the horizon: Cornel will be starting a new mosquito-borne virus project in February. He received a Carnegie Foundation scholarly three-month fellowship to work in South Africa (February through to April). The primary objective of the project? To examine mosquito-borne viruses cycling in seven national parks in South Africa and two National Parks in Bostwana.
“It's extremely difficult to get permission to conduct field research in national parks in Southern Africa and this provides an unprecedented exciting opportunity for me to work with a friend, Professor Leo Braack from the University of Pretoria, in these parks. One has to be very careful working in some of these parks at night because of the wild predators, elephants, hippos and buffalo.”
Cornel is active in the 30- member Center for Vectorborne Diseases (CVEC), headquartered in the UC Davis School of Veterinary Medicine and considered the most comprehensive vectorborne disease program in California. Both interdisciplinary and global, CVEC encompasses biological, medical, veterinary and social sciences.
Medical entomologist Anthony Cornel with a snake in Brazil.
UC Davis medical entomologists Anthony Cornel (foreground) and Gregory Lanzaro make annual trips to Mali to study malaria mosquitoes.
But then again medical entomologist Robert Washino isn't “most people.”
Washino, emeritus professor and former chair of the UC Davis Department of Entomology and former associate dean of the UC Davis College of Agricultural and Environmental Sciences, has just completed 38 years of service as a trustee of the Sacramento-Yolo Mosquito and Vector Control District (SYMVC) Governing Board.
And after 38 years, he's retiring from the board.
Washino has served longer than any other trustee in the history of the board. Indeed, that's almost four decades. The Davis City Council appointed him as the city's representative to the mosquito abatement board in 1973. It's a big district. The district covers 2000 square miles in Yolo and Sacramento counties.
The SYMVC board honored him at its Dec. 13th meeting, held in the district headquarters, Elk Grove, with a proclamation for his “exemplary public service and dedication to public health.” Next, the Davis City Council will present a proclamation at its meeting beginning at 6:30 p.m. Tuesday, Dec. 20 in the Community Chambers, 23 Russell Blvd.
Washino, now 79, served as president of the board five times during his tenure.
The SYMVC laboratory/library is named in his honor. Washino gifted his entire collection of mosquito-related books and journals, photographs and slides to the district for research and teaching purposes.
Internationally known for his expertise on mosquitoes, “Dr. Washino brought a perspective to the board that is difficult to replace,” SYMVC Manager David Brown said. “He is known worldwide for his work on mosquitoes and public health and bringing that knowledge to the district has provided a level of service that is hard to match. Without his guidance and tutelage, I am sure our program would not be as effective as it is today.”
One of the highlights of his career occurred in 2005 when he received the international Harry Hoogstraal Medal for Outstanding Achievement in Medical Entomology for his work on the ecology of mosquitoes and mosquito control agents.
He also has a mosquito named for him: Aedes washinoi.
"It's a tiny one," he says.
So, Bob Washino, mosquito man extraordinaire, is stepping down. We're not sure, though, that he can ever totally step down.
He has too much public service in his heart.
Culex quinquefasciatus, which can transmit West Nile virus. (Photo by Kathy Keatley Garvey)
Medical entomologist Robert Washino during his military years in the mid-1950s. This photo was taken in a lab south of Paris, France.
An article in the July 21st edition of Nature asked that very question.
Author Janet Fang, an intern in Nature's Washington, D.C., office, wrote that "Malaria infects some 247 million people worldwide each year, and kills nearly one million. Mosquitoes cause a huge further medical and financial burden by spreading yellow fever, dengue fever, Japanese encephaltis, Rift Valley fever, Chikungunya virus and West Nile virus."
So, how about a world without mosquitoes? "Would anyone or anything miss them?" she asked.
Fang went on to ask scientists that very question. But the fact is, they're here and they're not going anywhere--except over here to bite us.
Meanwhile, over in the UC Davis Department of Entomology, two graduate students just received William Hazelton Memorial Fellowship Awards to further their mosquito research.
Tara Thiemann (top photo), a doctoral candidate studying with major professor William Reisen, received $2100 for her statewide research on bloodfeeding patterns of Culex mosquitoes. She studies both urban and rural populations of mosquitoes and their host meals.
Jenny Carlson (bottom photo), an incoming doctoral student who will be studying with major professor Anthony 'Anton' Cornel, received $2000 for her research on avian malaria parasites.Thiemann's project involves analyzing the blood meals of Culex mosquitoes to identify specific host species--research important toward understanding both the maintenance and epidemic transmission of the West Nile virus.
Carlson’s research will take her to West Africa where she will collect mosquito vector and avian blood samples to study the mechanisms of malaria parasite transmission. She hypothesizes that the diversity of mosquito and avian parasites will be lower in deforested areas than forested areas.
The award memorializes William “Bill” Hazeltine (1926-1994), who managed the Lake County Mosquito Abatement District from 1961-64 and the Butte County Mosquito Abatement District from 1966-1992. He was an ardent supporter of the judicious use of public health pesticides to protect public health. He continued work on related projects until his death in 1994.
Hazeltine studied entomology in the UC Berkeley graduate program from 1950-53, and received his doctorate in entomology from Purdue University in 1962.
UC Davis medical entomologist Bruce Eldridge eulogized Hazeltine at the 2005 American Mosquito Control Association conference. His talk, "William Emery Hazelton II--Rebel With a Cause," was later published in the Journal of the American Mosquito Control Association. (See PDF)
It's good to know that Hazeltine's cause lives on through his family's generosity.
Chemical ecologist Walter Leal, professor and former chair of the UC Davis Department of Entomology, and his postdoctoral researcher Zain Syed have done it again.
In August of 2008, they discovered the secret mode of the insect repellent, DEET. In groundbreaking research published in the Proceedings of the National Academy of Sciences (PNAS), they found that DEET doesn't mask the smell of the host (that would be you and me), nor does DEET jam the insect's senses.
Mosquitoes CAN indeed smell DEET. They avoid it because they don't like the odor.
Then on Monday, Leal and Syed published more groundbreaking research, also in PNAS. They identified the dominant compound that attracts Culex mosquitoes to both birds and humans.
It's a compound called nonanal, naturally produced in birds and humans. This not only explains the host shift from birds to humans, but paves the way for key developments in mosquito and disease control.
Infected Culex mosquitoes transmit life-threatening diseases, including West Nile virus. Since 1999, the Centers for Disease Control and Prevention has recorded 29,397 human cases and 1,147 fatalities in the United States alone.
“Nonanal is how they find us,” Leal said. “The antennae of the Culex quinquefasciatus are highly developed to detect even extremely low concentrations of nonanal.”
Researchers from throughout the country this week praised their work.
Yale University professor John Carlson, a leading scientist in insect olfaction, described the study as “exciting with important implications for the intriguing question of how mosquitoes find the humans they bite.”
“Leal and Syed have identified a human odor that is detected with great sensitivity by the antennae of mosquitoes that transmit West Nile virus,” Carlson said. “In addition to its scientific interest, the study may have important practical applications in the control of these mosquitoes and the diseases they carry.”
Chemical ecologist Coby Schal, a professor at North Carolina State University, described the research as representing “some of the best research on insect olfaction that I have ever read. By combining trapping experiments in the field with careful characterization of the response profiles of antennal and maxillary sensilla of Culex mosquitoes, Syed and Leal show not only that the combination of carbon dioxide and nonanal is an important beacon for blood-seeking mosquitoes, but also that a large fraction of the sensilla on the mosquito’s nose (antennae) is dedicated to the detection of nonanal at incredibly low concentration.
“Such high sensitivity of olfactory receptor neurons to nonanal – rivaling the response characteristics of pheromone responsive neurons – suggests that nonanal has played an important role in the evolution of host-finding and host-preferences in Culex mosquitoes,” Schal said. “This is a truly exceptional achievement by the outstanding Syed/Leal team, but in step with their previous outstanding contributions on a wide range of arthropods.”
More information on the Leal lab research is on the Department of Entomology Web page.
Leal, a newly elected Fellow of the Entomological Society of America (he's one of 10 entomologists to be so honored this year) and Syed, named one of the top post-doctoral researchers at UC Davis this year, have indeed done it again.
When you think of all the havoc that mosquito-borne diseases have wreaked, this is the kind of research that definitely deserves a round of applause.
Dr. Leal and Dr. Syed are a highly efficient and effective SWAT team.
Walter Leal and Zain Syed
Chemical ecologist Zain Syed of the Walter Leal lab, University of California, Davis, knows just where to find mosquitoes for his research.
He's been collecting up to 3000 mosquitoes a night along the Yolo Causeway, located on Interstate 80 between Davis and West Sacramento. The Yolo basin is home to the Vic Fazio Yolo Wildlife Area.It's easy to catch mosquitoes.
Syed is using carbon-dioxide traps to capture host-seeking mosquitoes. The female skeeters are seeking a blood meal (you, if you're around there). His traps entice them to "come on in."
"Once mosquitoes are lured to the vicinity," Syed says, "a suction fan traps them and sends them to the sleeve, a mesh bag that holds mosquitoes."
The mesh bag below holds 2000 mosquitoes. They are mostly Culex tarsalis, but also some Culex pipiens.
Culex mosquitoes are known for transmitting West Nile virus.
Syed and Leal are known for uncovering the mode of action for DEET, the chemical insect repellent used by more than 200 million people worldwide. Their groundbreaking research last year found that DEET doesn't jam a mosquito's senses or mask the smell of the host, as scientists previously thought for some 50 years. Mosquitoes avoid DEET because it smells bad to them.
Syed recently won one of two coveted campuswide awards for excellence in postdoctoral research from a field of 800 postdocs.
But other fields--rice fields--have always drawn his attention.
That's where the skeeters are.