Man versus Mosquito Robert Novak and the INHS Medical Entomology Laboratory
by Dan Ferber(Posted August 7, 1998 · Issue 36)
Abstract
We tend to think of mosquitoes as being merely annoying, but many species
carry viral diseases that are both incurable and potentially deadly, and for
which there are no vaccines. Robert Novak and his team of entomologists hunt
mosquitoes in the wild and breed them in the lab, seeking to better
understand the dynamics and cycles of both disease and vector. The lab also
develops ecologically sound methods to control mosquito populations.
The morning air is warm and humid in the lush Louisiana woods, and pale light struggles to the forest floor. Eight hundred miles from home and quietly prowling the damp underbrush in search of hungry mosquitoes is Robert Novak, professor of entomology and head of the medical entomology program at the Illinois Natural History Survey (INHS). The mosquitoes, buzzing and dancing, alight on his bare arm. He quickly traps them with a power aspirator, a handheld vacuum that sucks the insects into a screened trap. Novak, a veteran mosquito hunter, has long since gotten used to the idea of himself as bait. To get the mosquitoes he needs, he'll do whatever it takes.
From the woods of Louisiana to the roadside ditches of Illinois, Robert Novak and his team of entomologists hunt mosquitoes and the potentially deadly viruses they carry - viruses that cause diseases like dengue fever, St. Louis encephalitis, and LaCrosse encephalitis. While antibiotics have contained many bacterial diseases, most mosquito-borne diseases have no vaccine and no cure. Even today, the best way to combat these diseases is to stop mosquitoes from biting people.
Over the
past ten years, Novak has pieced together a large and diverse team of biologists to understand and manage the mosquito. They use the tools of entomology, field ecology, and molecular biology to better understand the complex life cycles of potentially deadly mosquito-borne viral diseases. As the immediate former president of the American Mosquito Control Association, Novak also serves as an informal spokesman for the field of mosquito control. In the past two years, he's appeared on Good Morning America, the Today Show, CNN, and 20/20 to explain how people can avoid mosquito trouble. Novak's team also devises innovative and environmentally safe ways to control mosquitoes, using anything from bacteria toxins to soy oil. Novak's colleague Robert Washino, professor emeritus of entomology at the University of California at Davis, praises Novak's program. His research ranges from "very applied to very basic, and everything in between, and that's been very impressive," says Washino. "It's a very real passion that he has."
Novak's first scientific paper, published while he was still an undergraduate, was on the population genetics of ten species of Aedes mosquitoes. He earned a master's degree studying mosquito systems with Lewis Nielsen at the University of Utah. Nielsen's lab would go on mosquito collecting trips, camping in national parks for up to three weeks at a time. "The rule was every seventh day would be a motel with a shower," Novak says. After his master's, he earned a Ph.D. in entomology at the University of Illinois at Urbana-Champaign, under the tutelage of famed entomologist Robert Horsfall. Jimmy Olson, an entomologist at Texas A&M, was a contemporary of Novak's in Horsfall's lab. "It was the spawning ground for a number of very well-respected medical entomologists," Olson says. It was in Horsfall's lab that Novak began to take an ecological approach to mosquito-borne diseases. "Horsfall was a real wealth of information," Novak says. "Not only on geology, but on paleontology, plants, natural history. Going on a field trip with him was a super learning experience."
These days, Novak is aiming at an understanding of the complex disease cycle of St. Louis encephalitis, a viral disease that has vexed epidemiologists since 1933, when the first known outbreak killed 266 people. While only about 100 of the world's 3,000 species of mosquitoes spread diseases in man, their impact is huge: malaria infects over 300 million people and kills three million children annually, and the dengue virus infects 50 million people each year in tropical areas of the world.
But while all mosquito-borne disease offer huge practical challenges, the encephalitis viruses provide a chance to address fundamental issues of vector-borne diseases, Novak says. These arboviruses, which cause St. Louis
encephalitis, LaCrosse encephalitis, eastern equine encephalitis, and other
human and animal diseases, have much more complex life cycles. By understanding the dynamics of St. Louis and LaCrosse encephalitis viruses, Novak hopes to create an ecological paradigm to help understand the disease cycles of other viruses that infect both animals and humans. "I have a feeling that the model is going to be very complex," Novak says. "These viruses [and animals] have been working with each other [and] living together for millions of years, and they have developed good strategies for survival."
Many of the basic questions of St. Louis encephalitis - the ecological questions - have
still not been answered. Which animals harbor the virus in the years between outbreaks? Evidence of infection has been found in bats, birds, and armadillos. Which mosquito species move the virus among the animals? Four species of mosquitoes in the Culex genus are known to carry the virus, and several more may as well. In northern climes, what happens to the virus over the winter when adult mosquitoes hibernate or die? INHS ecologist Truls Jensen is trying to answer that question. "Between those summer outbreaks, we really don't know where the virus goes," Jensen says. "That's really been a challenge not just for St. Louis, but for a lot of mosquito-borne viruses. People have been looking for where the virus goes during the winter, and where the virus goes during the spring, for many, many years."
Like everyone in Novak's lab, Jensen returns to the field many times each year to collect mosquitoes and analyze their lifestyles. Jensen and other lab members trap adult mosquitoes with giant nets mounted on trucks, entice them into traps with the aroma of rotting vegetation, and collect their young while they are still larvae swimming around mud puddles and marshes. As Novak says, "Everything we do really originates in the field."
To track mosquito-borne viruses, you need a way to detect them in mosquitoes and animals. Until the early 1990s, detecting virus in mosquitoes was a laborious endeavor. About 50 mosquitoes would be trapped, ground up, and added to cultured mosquito cells. If the cells were killed, the virus had been present in one of the ground-up mosquitoes. But in 1992, INHS molecular biologist Michael Vodkin adapted the then-new technique of reverse transcriptase-polymerase chain reaction to detect the RNA genomes of arboviruses. The assay can detect a single virus particle in the leg of a single mosquito. The insect hobbles away to feed and breed again, and the scientist knows if it harbors the virus. Because the same assay can also detect virus in infected animals, it offers the best opportunity yet to discover where a mosquito-borne virus goes when it is not infecting people.
Armed with molecular and ecological tools, the INHS team is uncovering the secrets of encephalitis viruses. But for Novak, that's not enough. "The real challenge now is, how can we use this information?" he says. So Novak's team is developing new, environmentally safe ways to control mosquitoes and thus reduce disease. For mosquito-borne viral diseases, "the only effective management tool is mosquito control," Novak explains. But controlling mosquitoes is tougher than it used to be. Several decades after society's DDT debacle, mosquitoes must be managed without damaging the environment. It is a tremendous challenge. "We are not just nozzleheads," Novak says. "We do not go out just to kill bugs. Insects are one of the biggest biodiversity groups on the globe, and we are trying to develop ways to manage them."
To do this, INHS chemical ecologist Richard Lampman in Novak's lab has developed natural insecticides based on soy oil. Mosquito larvae live in standing water and surface to breathe. Soy-based oils spread on the surface of water, altering the surface tension and suffocating the larvae. By combining soy oil with surfactants to help it spread, or a bacterial toxin that specifically kills mosquito larvae, Lampman hopes to develop a powerful, but environmentally benign, mosquito killer.
Back in the Louisiana woods, the mosquitoes are very much alive and biting, and Novak collects them undeterred. By the end of the three-day collecting trip, Novak, Jensen, and graduate student Mike Slamecka will have coolers full of mosquitoes and mosquito larvae, ready to breed in colonies back at the lab. The trip is one of many the team will make over the summer, braving the elements and the insects in marshes, fields, and woods. It's one more step toward helping us understand and manage the pesky - and potentially dangerous - mosquito. "I have no problem putting together the work we're doing on the soybean oils, the molecular work," Novak says. "To me it's all one big picture."
Dan Ferber is a freelance science writer based in Urbana, Illinois.
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Yellow Fever - an HMS Beagle Featured Essay on the yellow fever plague of the
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showed that the disease was carried by mosquitoes.
The morning air is warm and humid in the lush Louisiana woods, and pale light struggles to the forest floor. Eight hundred miles from home and quietly prowling the damp underbrush in search of hungry mosquitoes is Robert Novak, professor of entomology and head of the medical entomology program at the Illinois Natural History Survey (INHS). The mosquitoes, buzzing and dancing, alight on his bare arm. He quickly traps them with a power aspirator, a handheld vacuum that sucks the insects into a screened trap. Novak, a veteran mosquito hunter, has long since gotten used to the idea of himself as bait. To get the mosquitoes he needs, he'll do whatever it takes.
Over the
past ten years, Novak has pieced together a large and diverse team of biologists to understand and manage the mosquito. They use the tools of entomology, field ecology, and molecular biology to better understand the complex life cycles of potentially deadly mosquito-borne viral diseases. As the immediate former president of the 
But while all mosquito-borne disease offer huge practical challenges, the encephalitis viruses provide a chance to address fundamental issues of vector-borne diseases, Novak says. These arboviruses, which cause St. Louis
encephalitis, LaCrosse encephalitis, eastern equine encephalitis, and other
human and animal diseases, have much more complex life cycles. By understanding the dynamics of St. Louis and LaCrosse encephalitis viruses, Novak hopes to create an ecological paradigm to help understand the disease cycles of other viruses that infect both animals and humans. "I have a feeling that the model is going to be very complex," Novak says. "These viruses [and animals] have been working with each other [and] living together for millions of years, and they have developed good strategies for survival."
To track mosquito-borne viruses, you need a way to detect them in mosquitoes and animals. Until the early 1990s, detecting virus in mosquitoes was a laborious endeavor. About 50 mosquitoes would be trapped, ground up, and added to cultured mosquito cells. If the cells were killed, the virus had been present in one of the ground-up mosquitoes. But in 1992, INHS molecular biologist Michael Vodkin adapted the then-new technique of reverse transcriptase-polymerase chain reaction to detect the RNA genomes of arboviruses. The assay can detect a single virus particle in the leg of a single mosquito. The insect hobbles away to feed and breed again, and the scientist knows if it harbors the virus. Because the same assay can also detect virus in infected animals, it offers the best opportunity yet to discover where a mosquito-borne virus goes when it is not infecting people.
To do this, INHS chemical ecologist Richard Lampman in Novak's lab has developed natural insecticides based on soy oil. Mosquito larvae live in standing water and surface to breathe. Soy-based oils spread on the surface of water, altering the surface tension and suffocating the larvae. By combining soy oil with surfactants to help it spread, or a bacterial toxin that specifically kills mosquito larvae, Lampman hopes to develop a powerful, but environmentally benign, mosquito killer. 
