Travelers know Iquitos as the "capital of the Peruvian Amazon" but scientists know it as a hot spot for dengue, a mosquito-borne viral disease with raging outbreaks in many tropical and subtropical countries.
Amy Morrison, stationed in Iquitos full-time, has directed dengue research activities there for the past 15 years. An epidemiologist who joined the UC Davis laboratory of medical entomologist Thomas Scott (now professor emeritus) in 1996, she's a project scientist and scientific director of the Naval Medical Research Unit No. 6 (NAMRU-6) Iquitos Laboratory.
Morrison is back in the states to present a UC Davis seminar on "Targeting Aedes Aegypti Adults for Dengue Control: Infection Experiments and Vector Control in Iquitos" from 4:10 to 5 p.m., Wednesday, Jan. 10, in 122 Briggs Hall, Kleiber Hall Drive.
Hosted by the UC Davis Department of Entomology and Nematology, it's the first in a series of winter seminars coordinated by assistant professor Rachel Vannette and Ph.D student Brendon Boudinot of the Phil Ward lab.
Dengue is a threat to global health, says Morrison, who holds a doctorate in epidemiology from Yale University and a master's degree in public health from UCLA. According to the World Health Organization (WHO), the incidence of dengue has increased 30-fold over the last 50 years and almost half of the world population is now at risk. It's ranked as "the most critical mosquito-borne viral disease in the world."
"Each year, an estimated 390 million dengue infections occur around the world," according to the World Mosquito Program. "Of these, 500,000 cases develop into dengue hemorrhagic fever, a more severe form of the disease, which results in up to 25,000 deaths annually worldwide."
Of the dengue project in Iquitos, Morrison says: "Comprehensive, longitudinal field studies that monitor both disease and vector populations for dengue viruses have been carried out since 1999 in Iquitos. In addition, to five large scale-vector control intervention trials, ongoing data collection has allowed the evaluation of Ministry of Health emergency vector control using indoor ULV space sprays with pyrethroids in concert with larviciding through multiple campaigns, as well as characterize local DENV (dengue virus) transmission dynamics through two and one novel DENV serotype and strain invasions into the city."
"Our research group has also been conducting contact cluster investigations on DENV-infected and febrile control individuals since 2008," Morrison relates. "These studies demonstrated that attack rates were consistent between houses where cases were first detected and recently visited contact houses independent of distance between these locations. Furthermore, contact cluster investigations allow us to identify viremic individuals across the spectrum of disease outcomes including inapparent infections."
"Using DENV positive individuals captured through these and other febrile surveillance protocols, we exposed laboratory reared (F2) Aedes aegypti mosquitoes directly on their arms or legs, and obtained blood samples with and without EDTA for exposure of mosquitoes in an artificial membrane feeder. After a 58-participant pilot study comparing feeding methods, we initiated a direct feeding protocol exposing participants (78 feeds in 31 participants to date). Feeding, survival, midgut infection and systemic dissemination are all higher using direct feeding than indirect feeding methods. Of 22 participants without detectable fluorescent focus assay titers in their serum at the time they were exposed to mosquitoes, 14 infected mosquitoes by at least one method."
"Although virus titer was a predictor of mosquito infection, mosquitoes became infected at low or undetectable titers and with subjects experiencing mild disease. We have evaluated insecticide-treated curtains and a novel lethal ovitrap (Attractive Lethal OviTrap = ALOT) for dengue control. Only the ALOT traps showed a significant impact on dengue incidence corresponding to a modest decrease in vector densities and a shift of the mosquito population age structure in the trap area to younger mosquitoes. Recent evaluations of indoor ULV interventions with pyrethroids suggest that ULV campaigns that reduce Aedes aegypti for at least 3 weeks through multiple fumigation cycles can mitigate DENV transmission during the same season."
Bottom line: "We argue that Aedes aegypti control should focus on interrupting transmission rather than long-term suppression at operationally unachievable levels and that emergency control should be applied at area-wide scales rather than reacting to individual DENV cases."
Chemical ecologist and mosquito researcher Walter Leal, distinguished professor in the UC Davis Department of Molecular and Cellular Biology, and his lab collaborated with scientists in Recife to ask “Does Zika Virus Infection Affect Mosquito Response to Repellents?”
The work, funded by the National Institutes of Health, was published Feb. 16 in Scientific Reports of the journal Nature. The researchers used mosquitoes originating from colonies reared by UC Davis medical entomologist Anthony Cornel and from colonies in Recife.
“We used assays mimicking the human arm to test the mosquitoes infected with the Zika virus,” Leal said, “and we asked whether the Zika infection affects mosquito response to repellents.” They tested DEET and Picaridin, considered the top two mosquito repellents. “We discovered that DEET works better than Picaridin against the southern house mosquito, Culex quinquefasciatus, and the yellow fever mosquito, Aedes aegypti, whether infected or not.”
The researchers also found that old mosquitoes that already had a blood meal “were less sensitive to repellents,” said Leal, adding “It was not clear whether this was due to the virus, but mostly likely because of age. ”
“Lower doses--normally used in commercial products--work well for young mosquitoes,” Leal said, “but the old ones are the dangerous ones because they may have had a blood meal infected with virus and there was enough time for the virus to replicate in the mosquito body.”
“The bottom line: to prevent bites of infected mosquitoes, higher doses of repellent are needed. The data suggest that 30 percent DEET should be used. Lower doses may repel nuisance young mosquitoes, but not the dangerous, infected, old females.”
Leal, a native of Brazil, collaborates with Rosangela Barbosa and Constancia Ayres of the Oswaldo Cruz Foundation (FIOCRUZ-PE), Recife, Brazil. The work with infected mosquitoes was conducted at FIOCRUZ-PE.
Leal, Barbosa and Ayres co-authored the paper with Fangfang Zeng and Kaiming Tan, both of the Leal lab; and Rosângela M. R. Barbosa, Gabriel B. Faierstein, Marcelo H. S. Paiva, Duschinka R. D. Guedes, and Mônica M. Crespo, all of Brazil.
The World Health Organization (WHO) recommends that people traveling to or living in areas with Zika virus (ZIKV) outbreaks or epidemics adopt preventive measures, including the use of insect repellents, to reduce or eliminate mosquito bites. Prior to the Feb. 16 published research, it was not known whether the most widely repellents are effective against ZIKV-infected mosquitoes, “in part because of the ethical concerns related to exposing a human subject's arm to infected mosquitoes in the standard arm-in-cage assay,” the researchers pointed out.
They used a previously developed, human subject-free behavioral assay, which mimics a human subject to evaluate the top two recommended insect repellents.
Scientists isolated the Zika virus (ZIKV) nearly seven decades ago from a sentinel rhesus monkey while they were trying to unravel the cycle of sylvan yellow fever virus in Uganda..
According to the Centers for Disease Control and Prevention:
- Zika is spread mostly by the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus). These mosquitoes bite during the day and night. The virus can also be sexually transmitted.
- Zika can be passed from a pregnant woman to her fetus. Infection during pregnancy can cause certain birth defects.
- There is no vaccine or medicine for Zika.
- Local mosquito-borne Zika virus transmission has been reported in the continental United States.
It's good to see UC Davis mosquito researchers featured in the KQED's science program, "Deep Look."
KQED journalists recently traveled to the UC Davis campus to visit several mosquito labs. The end result: The KQED news article on “How Mosquitoes Use Six Needles to Suck Your Blood,” which includes an embedded video. The National Public Radio's health blog, “Shots,” includes a shorter version. You can also see the Deep Look video on YouTube (embedded below).
- Parasitologist and entomologist Shirley Luckhart, professor in the UC Davis School of Medicine's Department of Medical Microbiology and immunology and the Department of Entomology and Nematology
- Medical entomologist Gregory Lanzaro, professor, Department of Pathology, Microbiology and Immunology (PMI), UC Davis School of Veterinary Medicine, and an associate of the UC Davis Department of Entomology and Nematology
- Chemical ecologist Walter Leal, professor in the UC Davis Department of Molecular and Cellular Biology and former chair of the UC Davis Department of Entomology
- Virologist Lark Coffey of PMI
- UC Davis post-doctoral researcher Young-Moo Choo of the Leal's lab who discovered a receptor by dissecting mosquitoes' mouthparts and genetically testing them.
“Mosquitoes don't find the blood vessel randomly," Leal said, pointing out that the receptors respond to chemicals in the blood.
The receptor that the Leal lab discovered is called 4EP, and may lead to drug companies developing new mosquito repellents. “First they'd need to find a repellent against the receptors," Choo told Quirós. "Then they'd treat people's skin with it. When the mosquito tried to penetrate the skin, it would taste or smell something repulsive and fly away.”
But back to the video. The narrator reveals the sophisticated tools that the mosquito uses to draw your blood.
- A protective sheath retracts: inside are six needles, and two of them have sharp, tiny teeth
- The mosquito uses the sharp, toothed needles to saw through your skin
- Other needles hold the tissues apart while she works
- Receptors on the tip of one of her needles guide her to your blood vessel.
- She uses the same needle like a straw to sip your blood
- She uses another needle to spit chemicals into you so your blood will flow easily. That's what gives you the itchy, scratch-me-now welts.
Of course, it's the viruses or parasites that the mosquito transmits that can sicken and kill us. Depending on the species, they give us such diseases as malaria, dengue, yellow fever, West Nile virus, Zika virus and elephantiasis.
As KQED says "This is the deadliest animal in the world. Mosquitoes kill hundreds of thousands of people each year...the most vulnerable people: children and pregnant women."
KQED performed an excellent public service in reporting and sharing this scientific information, gleaned from the UC Davis labs. The first day the video was posted, it drew nearly 400,000 views.
We worry about what mosquitoes do to us. If mosquitoes could talk--if they could communicate with us--they ought to be worried about what we're going to do to them.
(Access the American Mosquito Control Association website to learn the biology of mosquitoes.)
First, there's the upcoming free public event, the Zika Public Awareness Symposium, set Thursday, May 26 from 6:30 to 8:30 p.m. in Room 1001 of Giedt Hall. Professor Walter Leal of the Molecular and Cellular Biology and 18 of his biochemistry students are organizing it. Leal, a chemical ecologist, collaborates with fellow mosquito researchers in his native Brazil.
Secondly, medical entomologist Greg Lanzaro, a professor in the the UC Davis Department of Pathology, Microbiology and Immunology, will speak on “Mendel, Mosquitoes and Malaria: Applying Modern Genetics to Control an Ancient Disease” at a Davis Science Café presentation at 5:30 p.m., Wednesday, June 8 in the G Street Wunderbar, 228 G St., Davis. It's free and open to the public.
The third event is not a pending event, but a pivotal one. It's a TEDx must-watch-and-share presentation by graduate student Ralph Washington Jr. of the UC Davis Department of Entomology and Nematology. His topic: "Science, Poverty, and the Human Imagination." He mentions his fascination with mosquitoes, including Aedes aegypti, the mosquito that transmits dengue, yellow fever, chikungunya and Zika viruses.
First, a little about each:
"It is very important that students and the public-at-large learn how to prevent a possible Zika epidemic as this is the first virus known to be transmitted both sexually and by mosquitoes," said coordinator Walter Leal, a chemical ecologist and professor in the UC Davis Department of Molecular and Cellular Biology and former chair of the UC Davis Department of Entomology.
"We thought that we did not have the vector (the yellow mosquito), but now our research in collaboration with Brazilian scientists indicates that our local mosquitoes (Culex) are also competent vectors," Leal said. "And more and more we hear cases of travelers returning home infect with Zika virus. I am so glad that a group of 18 students who took my biochemistry class last quarter decided to launch this initiative to educate their peers and citizens of Davis about this dangerous virus."
The scientific-based symposium will include expert panels and speakers throughout the United States and the world, including those working on the front lines of the Zika epidemic.
The Zika Epidemic – An Overview
Professor Walter S. Leal
UC Davis Department of Molecular and Cellular Biology
Congenital Zika Syndrome
Dr. Regina Coeli Ramos, University of Pernambuco, Brazil (remote)
Zika Virus and Me
Professor Brian Foy
Department of Microbiology, Immunology, and Pathology, Colorado State University
Zika Virus: Looking into Mosquitoes' Vectorial Capacity
Professor Constância F. J. Ayres
Department of Entomology, Fundação Oswaldo Cruz-Pernambuco, Brazil (remote)
Don't Let Mosquitoes Bug You with Zika – Repel Them
Professor Walter S. Leal
UC Davis Department of Molecular and Cellular Biology
DEET vs. Zika – I Would Go with the Former
Dr. Emanual Maverakis
Department of Dermatology, UC Davis School of Medicine
Keeping Mosquito at Bay, Not in Your Backyard
Dr. Paula Macedo
Laboratory Director, Sacramento-Yolo Mosquito & Vector Control District
Friends Don't Let Friends Get Zika
Dr. Stuart H. Cohen
Chief of the Division of Infectious Diseases and director of Hospital Epidemiology and Infection Control, UC Davis Medical School.
Attendance to the symposium is free, but due to limited space, those planning to attend are asked to RSVP to firstname.lastname@example.org.
'Mendel, Mosquitoes and Malaria: Applying Modern Genetics to Control an Ancient Disease': Wednesday, June 8, G Street Wunderbar, Davis
UC Davis medical entomologist Greg Lanzaro, a professor in the the UC Davis Department of Pathology, Microbiology and Immunology, UC Davis School of Veterinary Medicine, is the invited speaker at the Davis Science Café presentation at 5:30 p.m., Wednesday, June 8 in the G Street Wunderbar, 228 G St., Davis.
The event, billed as "A Conversation with Professor Lanzaro," will be hosted by Professor Jared Shaw of the UC Davis Department of Chemistry. Shaw founded the Davis Science Café in 2012. It's held the second Wednesday of each month and is free and open to the public. This is a good opportunity to learn more about mosquitoes and the research underway.
Lanzaro, a noted malaria mosquito researcher, is the former director of the UC Statewide Mosquito Research Program. Science Café is affiliated with the Capital Science Communicators.
This is an inspiring presentation by Ralph Washington Jr., a National Science Foundation Graduate Research Fellow, and a second-year Ph.D. student in Entomology and Nematology. He chairs the UC Davis Graduate Student Association, co-chairs the UC Council of Student Body Presidents, and is one of the leaders of the UC Davis Black Graduate and Professional Students Association. He is committed to science and social justice and seeks a career as a research professor. He seeks to encourage children, especially low-income children, to study science. (Watch video on TEDx) (Watch video on YouTube)
In his presentation, Washington, who grew up in Oak Park, an impoverished Sacramento neighborhood, says that "The most important thing you should know about my childhood, is that I once knew hunger so well that the pangs were my closest friends. I was hungry for food, I was hungry for emotional stability and I also was hungry for knowledge."
He goes on to talk about children's innate curiosity and that we need to give them "the spark to ignite their imagination."
Mosquitoes also enter the picture. “Mosquitoes have very interesting biology," Washington says. "Some spend winter frozen in blocks of ice whereas others develop in lakes as alkaline as ammonia, more than twice as salty as seawater and as hot as a scalding shower. Some develop in empty snail shells or the tops of concave mushrooms or in a horse's hoof prints."
Be sure to tune in to hear what Washington says about several mosquitoes, including Aedes aegypti and its courtship. You'll remember what he says the next time a mosquito buzzes around you./span>
He feuded with fellow entomologists, was a bigamist (married to two wives at the same time) and caused an uproar when a tunnel he dug in a Washington, D.C. alley collapsed in 1924 and some declared it the work of German spies.
All that will come to light on Thursday, April 28 at UC Davis when entomologist Marc E. Epstein talks about his newly published book on Dyar's eccentric life, Moths, Myths and Mosquitoes: The Eccentric Life of Harrison G. Dyar, Jr.
Epstein will present a lecture and book signing from 7:15 to 8:45 p.m., in the International House, 10 College Park, Davis.
The event, free and open to the public, is co-sponsored by Jay Rosenheim, professor of entomology, UC Davis Department of Entomology and Nematology, and by his department. Epstein is a longtime research associate and friend of Rosenheim's.
“As far as how I got into doing research on Dyar, at the onset it was related to my dissertation at University of Minnesota on Limacodidae (family of slug caterpillar moths, so called because their caterpillars bear a distinct resemblance to slugs),” Epstein said.
This led to Epstein and Henson to writing the American Entomologist article “Digging for Dyar: the Man behind the Myth.”
“Since the article appeared in 1992 I've accumulated a lot more information about Dyar, his genealogy, and even more significant connections between him and his favorite moths,” Epstein said.
The book, published by Oxford University Press, will be available for purchase at Epstein's talk.
Epstein is a senior insect biosystematist for the order Lepitopdera (butterflies, moths) with the Plant Pest Diagnostics Branch, California Department of Food and Agriculture. He is a research associate for the National Museum of Natural History (NMNH), Smithsonian Institution.
Harrison G. Dyar Jr. (1866-1929) was a Smithsonian entomologist of the early 20th century. He was a taxonomist who published extensively on moths and butterflies, mosquitoes, and sawflies. As a teenager, he studied insects, particularly moths. He received his bachelor's degree in chemistry in 1889 from the Massachusetts Institute of Technology, and his master's degree in biology from Columbia University in 1894. His doctoral dissertation (1895) dealt with airborne bacteria in New York City.
Oxford University offers this description of Moths, Myths and Mosquitoes:
"On September 26, 1924, the ground collapsed beneath a truck in a back alley in Washington, D.C., revealing a mysterious underground labyrinth. In spite of wild speculations, the tunnel was not the work of German spies, but rather an aging, eccentric Smithsonian scientist named Harrison Gray Dyar, Jr. While Dyar's covert tunneling habits may seem far-fetched, they were merely one of many oddities in Dyar's unbelievable life."
"For the first time, insect biosystematist Marc E. Epstein presents a complete account of Dyar's life story. Dyar, one of the most influential biologists of the twentieth century, focused his entomological career on building natural classifications of various groups of insects. His revolutionary approach to taxonomy, which examined both larval and adult stages of insects, brought about major changes in the scientific community's understanding of natural relationships and insect systematics. He was also the father of what came to be known as Dyar's Law, a pragmatic method to standardize information on insect larval stages as they grow. Over the course of his illustrious career at the U.S. National Museum, Smithsonian Institution from 1897-1929, Dyar named over 3,000 species, established the List of North American Lepidoptera, an unrivaled catalog of moths and butterflies, and built one of the nation's premier Lepidoptera and mosquito collections."
Epstein researches and writes on evolution and classification of moths and their biodiversity, and develops identification tools for moths that threaten agriculture. He served with NMNH's Department of Entomology (1988-2003), co-founding the department's Archives and Illustration Archives. He received his master's degree (1982) and doctorate (1988) from the University of Minnesota.
For more information on the April 28th event, contact Jay Rosenheim at email@example.com.