The species has spread to at least seven counties in California since June 2013, says UC Davis medical entomologist Anthony Cornel of the UC Kearney Agricultural Research and Extension Center, Parlier, and the UC Davis Department of Entomology.
“It's an issue of great concern, especially as current control methods do not appear to be working well," says Cornel, who collaborates on research projects in Clovis, Fresno County, with the Consolidated Mosquito Abatement District. The district, based in Fresno, covers 1,058 square miles, including part of Kings County.
“We can't predict how far this mosquito will go in California,” he says, but it has spread “south of Fresno to San Diego. The furtherest 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.”
As far north as Sacramento?
“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.”
Infected Aedes aegypti can transmit dengue, yellow fever, Zika and chikungunya viruses. The Zika virus 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.
Although the mosquito species is in California, it's important to point out that there are no reported cases of locally transmitted Zika virus in the state or in 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 and his colleagues published a 27-slide document, “Surveillance and Control of Aedes aegypti Mosquito in Clovis, Calif.,” on Feb. 8 in F1000 Research, http://f1000research.com/slides/5-149. They called attention to the widespread invasion and establishment of the species in California. The research, illustrated with maps, is the 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.
The California team collaborates 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 explains. “It's not new, but it's not been employed in large trials.”
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 says. “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 points 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.”
It's crucial for the public to become involved, Cornel emphasizes. “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.
It was just a matter of time before the so-called "super mosquito" surfaced, resulting in the failure of insecticide-treated nets to provide meaningful control from malaria in some localities in Africa.
"It's a ‘super' with respect to its ability to survive exposure to the insecticides on treated bed nets,” said medical entomologist Gregory Lanzaro, director of the Vector Genetics Laboratory at the School of Veterinary Medicine, University of California, Davis, who led the research team.
He and his colleagues recently discovered that interbreeding of two malaria mosquito species in the West African country of Mali, has resulted in “a super mosquito” hybrid that's resistant to insecticide-treated bed nets.
Anopheles gambiae, a major malaria vector, is interbreeding with isolated pockets of another malaria mosquito, A coluzzii.
The research, published in “The Proceedings of the National Academy of Sciences, “provides convincing evidence indicating that a man-made change in the environment--the introduction of insecticides--has altered the evolutionary relationship between two species, in this case a breakdown in the reproductive isolation that separates them,” said Lanzaro, a professor in the Department of Pathology, Microbiology and Immunology in the School of Veterinary Medicine.
Lanzaro and his "blood brother" medical entomologist Anthony Cornel of the Department of Entomology and Nematology have been researching mosquitoes in Mali since 1991.
Lanzaro called the need to develop new and effective malaria vector control strategies "urgent.”
Said Lanzaro: "A number of new strategies are in development, including new insecticides, biological agents--including mosquito killing bacteria and fungi--and genetic manipulation of mosquitoes aimed at either killing them or altering their ability to transmit the malaria parasite. These efforts need to be stepped up.”
The paper is titled “Adaptive Introgression in an African Malaria Mosquito Coincident with the Increase Usage of Insecticide-Treated Bed Nets.” First author is Laura Norris, then a postdoctoral scholar in the UC Davis Department of Entomology and Nematology who was supported by a National Institutes of Health T32 training grant awarded to Lanzaro. Norris has since accepted a position with the President's Malaria Initiative in Washington, D.C.
In addition to Lanzaro and Cornel, the co-authors include Yoosook Lee and Travis Collier of the Vector Genetics Lab and the Department of Pathology, Microbiology and Immunology; and Abdrahamane Fofana of the Malaria Research and Training Center at the University of Bamako, Mali. Three grants from the National Institutes of Health funded the research.
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.
This year's event, set Wednesday, April 25 from 9 a.m. to 4 p.m. in Room 1031 of the Gladys Valley Hall, School of Veterinary Medicine, will include presentations on the historical, current and future efforts of malaria control, as well as updates on other vector biology research.
The UC Davis World Malaria Day is an opportunity "for students and researchers engaged in vector biology and genetics research to come together to discuss their research efforts,” said spokesperson Michelle Sanford, a postdoctoral scholar in the UC Davis Vector Genetics Lab.
The event supports World Malaria Day and the Roll Back Malaria Program in promoting education and research in the fight against malaria.
How did the UC Davis World Malaria Day observance originate? It was launched in 2007 by the (now folded) UC Mosquito Research Program, a UC Agricultue and Natural Resources program based in the UC Davis Department of Entomology and directed by medical entomologist Gregory Lanzaro. Lanzaro is now a professor in the Department of Pathology, Microbiology and Immunology of the School of Veterinary Medicine.
For the last several years, the Vector Genetics Lab has funded the World Malaria Day observance through a National Institutes of Health training grant.
Lanzaro and his "blood brother" medical entomologist Anthony Cornel direct the Vector Genetics Lab research programs. They've been doing research in Africa together for years. Cornel is an associate professor in the UC Davis Department of Entomology and a mosquito researcher at the Kearney Agricultural Research and Extension Center, Parlier.
The target: malaria, a mosquito-borne disease caused by infected Anopheles mosquitoes transmitting Plasmodium parasites.
The bad news is that more than half of the world's population is at risk for malaria. According to the World Malaria Report 2011, more than 216 million cases of malaria and an estimated 655 000 deaths occurred worldwide in 2010. Children in Africa are the still most susceptible to malaria; a child dies every minute of the disease.
The good news: Due to investments in malaria control, malaria mortality rates have dropped by more than 25 percent globally since 2000. Statistics show that malaria deaths in Africa have been cut by one-third within the last decade, according to the World Health Organization (WHO).
The strides we're making in tackling this massive killer are reflected in this year's World Malaria Day theme: "Sustain Gains, Save Lives: Invest in Malaria."
Sustain. Save. Invest. Well said.
Postdoctoral researcher Rebecca “Becky” Trout-Fryxell (right), who studies Culex and Anopheles mosquitoes with University of California, Davis medical entomologists Anthony Cornel and Gregory Lanzaro, just received an award designating her as one of the top young entomologists in the nation.
Trout-Fryxell won one of the five John Henry Comstock Graduate Student Awards presented at the Entomological Society of America’s 58th annual meeting, held recently in San Diego. The Southwestern Branch of ESA selected her at its most outstanding entomology graduate student in a region encompassing Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee, plus the U.S. territories of Puerto Rico and the U.S. Virgin Islands.
The other four ESA branches—Pacific, Eastern, North Central, and Southwestern Branch—also each selected a recipient.
Trout-Fryxell works with population genetics of the West Nile virus vector Culex pipiens, and does research on the malaria mosquito, Anopheles gambiae.
Fryxell joined the UC Davis team in April of 2009. Cornel is an associate professor of entomology, with offices and labs at UC Kearney Agricultural Center, Parlier, and UC Davis. Lanzaro is a professor in the Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine.
Trout-Fryxell previously won a Isley-Duport Entomology Scholarship and was a member of the 2007 Linnaean Games National Championship team from the University of Arkansas. The Linnaean Games is a college bowl-type competition featuring questions about insects, entomologists and entomological facts.
Trout-Fryxell has published her research in Journal of Medical Entomology, Journal of American Mosquito Control, Emerging Infectious Diseases, Medical and Veterinary Entomology, among others, on topics ranging from mosquitoes and ticks to bed bugs.
Trout-Fryxell received her master’s degree in entomology from the University of Kentucky, Lexington, where she studied with major professor Grayson Brown. Her research focused on reducing mosquito populations in the peridomestic environment.
She received her doctorate in entomology from the University of Arkansas, Fayetteville, last May. Studying with major professors Dayton Steelman and Allen Szalanski, she completed her dissertation on the distribution and occurrence of ticks in Arkansas, also examining tick-host pathogen interactions.
The four other winners of the coveted John Henry Comstock Awards:
Pacific Branch: Ashfaq Sial, Washington State University
North Central Branch: Anna Fiedler, Michigan State University
Southwestern Branch: Joe Lewis, University of North Texas
Eastern Branch: Gaylord Desurmont, Cornell
Back, in 2008, mosquito researcher Christopher Barker of the William Reisen lab at UC Davis won the Comstock award from the Pacific Branch.
Davis is definitely a good place to be for mosquito research!