West Nile Project Wins Connecticut Brothers Top National Honors
South Windsor Students Capture First Place in Siemens Westinghouse Competition
[Note: This is an expanded version of the article that appears in the Bulletin of the Connecticut Academy of Science and Engineering, Vol. 19,1, Spring 2004]
With more than 9,000 cases of West Nile virus (WNV) reported nationwide in 2003 and more than 200 deaths, the virus is a hot topic in the summer months. Thanks to the efforts of two local students, now WNV is even getting national press coverage in the off-season.
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| Jeffrey, left, and Mark Schneider with their first place trophies at ceremonies in Washington, DC last December.
(Photo credit: Justin Allardyce Knight. Photo courtesy: Siemens Foundation) |
“The reaction to our work has been amazing,” Jeff Schneider said. “We had no idea when we started this project that it would go this far. No idea at all.”
WNV, a significant health threat, was first discovered in 1937 in the West Nile district of Uganda. In 1999, the first ever occurrence of the virus in the Western Hemisphere occurred in New York City. By 2002, the virus had spread to 44 states and resulted in more than 4000 cases and 284 deaths.
The Schneiders’ project sprang out of a typical teenage penchant for wanting to prove their mother wrong. “I’m very susceptible to mosquito bites, so in late summer, my mom is always telling me to wear long pants so that I don’t get the West Nile virus,” Jeff said. “One day Mark and I were talking and we wondered what the chances really were that I’d contract the virus. The idea for our project kind of grew from there.”
The purpose of the project was to develop an analytical model describing the transmission of WNV. “We developed a computer simulation to evaluate the factors affecting the propagation of the virus using a computer model called STELLA 7.02,” Mark said.
According to the Schneiders, one of the most difficult parts of their project was learning STELLA. Fortunately, their mentor and chemistry teacher, David White, had attended a two-week summer institute in 2002 where the STELLA (Structural Thinking Experiential Learning Laboratory with Animation) computer model was taught. The training expertise was offered at the University of Illinois at Champaign through the National Computational Science Leadership Program (NCSLP). The NCSLP is made possible by a grant from the National Science Foundation.
“My goal was to bring computational science into the classroom and into the curriculum,” White said. “When I got back to school that fall, I was approached by Jeff and Mark who expressed their interest in doing an independent study on the propagation of the West Nile virus. They wanted to research available data sources and try to develop a computer model of the various factors influencing West Nile virus propagation in the environment. I am not an epidemiologist or trained in the varieties of mosquito species and their breeding habits, but I know and understand the process of research science. I realized that because of their great desire to tackle this problem, Mark and Jeff would be perfect candidates to learn the basics of STELLA and then use what they learned to develop a sophisticated STELLA model of the West Nile virus propagation.”
White spent about ten hours with Jeff and Mark showing them the program and what it could do. “They took it from there,” he said. “They learned STELLA inside and out and then applied it to their project on their own. Jeff worked very hard to figure out how to put it together and apply it to their project, while Mark concentrated on researching existing information to support their model.”
“We spent hundreds of hours learning how to apply STELLA to our project,” Jeff said. “It was a lot of trial and error.”
The Schneiders incorporated four modules in their model: mosquito life cycle, blood meal-egg laying, West Nile virus transmission cycle and avian (bird) population dynamics.
“In the first module, we determined which mosquitoes spread the disease and, of those, which live in our area,” Jeff said. “Research showed that the Culex species (also known as the northern household mosquito) was the likely carrier in our area. We determined the length of their growth cycle and the effect of environmental conditions on their life cycle. For example, research indicates that when temperatures drop below 50 degrees Fahrenheit the life cycle is arrested. When the temperature hovers around 50 degrees, the mosquitoes take the longest to mature but live the longest. And, when the temperature approaches 90 degrees, the life cycle is at its fastest rate but the mosquitoes die most quickly.”
Given that only female mosquitoes blood feed, their second module established parameters that predict the number of female mosquito bites per mosquito generation. “The assumption is that a female can bite a maximum of three times in her lifetime,” Jeff explained. “We assumed that the blood-feeding events occurred at intervals of 5, 15 and 25 days after the mosquito emerges from the pupa stage. The model tracks the female population as a function of time. We assumed that all females bite once, fewer bite two times (because they die before getting a chance to bite again) and still fewer bite a third time.” The blood-feeding process is important since WNV is transmitted to the mosquito via biting an infected avian and only WNV-infected mosquitoes can transmit the disease.
The third module focused on the WNV transmission cycle. This module computes the number of WNV-infected mosquitoes and the population of infected birds. “We used probability models to determine the likelihood that a non-infected mosquito will bite an infected avian, and the likelihood that an infected mosquito will bite an uninfected avian. These equations led to realistic conclusions,” Jeff said. “For example, to determine the extent of the viral transmission to the mosquito we multiplied the number of uninfected mosquitoes by three factors: the fraction of infected birds, the probability that the mosquitoes would feed on avian hosts, and the probability that the blood-feeding event would infect the mosquito.” Transmission factors were based on results of research papers.
The fourth module tracked the infected and non-infected bird population in the area and identified which birds would be suitable hosts (food) for the Culex pipiens mosquito. “We determined that the primary host for this species is the American crow of which there are approximately 3 billion in the United States alone,” Jeff said. “The crow is a good indicator of West Nile virus because it amplifies the virus in its system making the virus more lethal to crows. Once a crow is bitten by an infected mosquito, it can transmit the virus to other mosquitoes when the other mosquitoes come to feed on the infected crow. While the model focused on crows, we also included the effect of migratory birds and local birds.”
“Jeff and Mark really spent a lot of time determining which factors to include and which are the most important in the transmission of this particular virus,” White said. “They read a lot of research materials and contacted key researchers throughout the United States.”
The model was validated against the 2000 WNV outbreak in Staten Island. The model demonstrated good agreement with observed crow deaths, peak infection period and fraction of infected mosquitoes. “We found that our model matched the data collected in the field fairly well,” Jeff said. For the year 2002, the model predicted 170 dead crows in Hartford County and data shows that the actual number was 184. The model also included secondary and tertiary factors to provide opportunities for further fine tuning.
After identifying the variables and establishing them as three levels in STELLA, they set the variables as “adjustable knobs” within the model. “As a result, people can use the knobs to perform sensitivity studies and to change model parameters,” Jeff said.
“We created a tool to help give a general idea of peak infection seasons – when and where the virus could strike and how intense the outbreak could be,” Jeff said. “This is good for the general public because people still don’t realize when the West Nile virus season starts. The first avian death from West Nile virus is usually reported in early- to mid-spring. The virus peaks earlier in the crow population. As infection spreads among the crows, the likelihood that humans will become infected increases. That’s why the peak of human cases occurs later in the summer.” While the mosquito that is responsible for spreading the virus is primarily orthophilic (preferring to feed on birds), it is an opportunistic feeder and also will bite humans.
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Mark and Jeffrey Schneider win the 2003-04 Siemens Westinghouse Competition Team Championship and are presented with their scholarship of $100,000, Pictured with the students are (from left to right): Albert Hoser, Chairman and CEO, Jack Bergen, President, Siemens Foundation; Kathie Olsen, lead judge, Mark Schneider, Bettina von Siemens, Jeffrey Schneider, and Peter von Siemens, Siemens Foundation board member. (Photo credit: Tony Rodriguez. Photo courtesy: Siemens Foundation) |
The Siemens Westinghouse Science Competition, now in its fifth year, is a signature program of New Jersey-based Siemens Foundation. The competition is administered by the College Board. Entries are judged at the regional level by esteemed scientists and faculty from six leading research universities, which also host the regional competitions: Carnegie Mellon University, University of Notre Dame, University of California – Berkeley, Massachusetts Institute of Technology, Georgia Institute of Technology, and The University of Texas at Austin.
The national finals of the Siemens Westinghouse Science Competition were judged by a panel of prominent scientists and mathematicians headed by lead judge Dr. Kathie L. Olsen, Associate Director, Office of Science and Technology Policy, Executive Office of the President, and the former Chief Scientist at NASA.
“It’s an honor to judge such a prestigious competition and a pleasure to be part of honoring our nation’s best and brightest young scientists and mathematicians,” said Dr. Olsen. “The Siemens competition offers promising high school students the opportunity to realize their dreams and pursue academic training and careers in the sciences. These are important goals that will help provide our nation with the next generation of leaders in math and science.”
Nineteen students competed in the national finals, including six individuals and six teams.
“Mark and Jeffrey Schneider set out to tackle a major public health challenge based on their personal experience of how West Nile virus threatened their own hometown,” said judge Dr. Thomas R. Eng, president of EvaluMetrix LLC and president of eHealth Institute. “Their work may help public health professionals make better decisions about this growing health threat. This is the kind of innovative research we need in public health.”
Jeff and Mark say their plans for the future include continuing to refine their model, noting that other variables could be added including effect of mosquito predators such as bats and dragonflies, as well as the impact of drought. “Data suggests that periods of drought followed by periods of increased rain can encourage the spread of the disease,” Mark said. “Long droughts will reduce mosquito predators while delayed rains may then rapidly increase the mosquito population. These mosquitoes interact with infected and uninfected avian populations concentrated near limited water sources, thereby spreading the disease more rapidly,” Mark said.
The two also are working with White on a book explaining how to use STELLA for various applications. The three think they might be on the cusp of a new trend toward using STELLA for population modeling. “Our book will be a kind of Idiot’s Guide to Using Stella,” Mark quipped. The book is slated to be written by December of 2004.
As for White, he says that Mark and Jeff are his “poster students” for a program of project-based learning that he is promoting as an integral part of the science curriculum at South Windsor High School. “Mark and Jeff have not only set the bar high but, more importantly, they have demonstrated that desire, drive and determination can have more impact on success in science than achieving an ‘A’ in the classroom,” he said.
An Update on WNV in Connecticut
In 1997, the Connecticut Agricultural Experiment Station (CAES) established a 36-site mosquito trapping program in response to the detection of an unusually high level of Eastern Equine Encephalitis (EEE) virus activity in mosquitoes in southeastern Connecticut in September of 1996. These monitoring sites were established in habitual mosquito habitats including swampy areas.
“Because we already had a monitoring program in place in 1999, we collected mosquitoes infected with West Nile virus just 10 days after The New York Times reported the first human cases of the virus in New York City,” said Academy member John Anderson, director of CAES.
“The following year, we tripled the locations of our mosquito traps and increased the variety of trap locations to include urban areas,” said Theodore Andreadis, chief medical entomologist at CAES, who heads Connecticut’s mosquito trapping program. The program now includes 91 permanent trapping stations statewide, one-third of which are located in Fairfield and New Haven counties. Mosquitoes trapped are screened for a variety of viruses that have the potential to cause human illness and disease including EEE, WNV, Jamestown Canyon, Cache Valley, Lacrosse and Trivittaus.
The WNV Surveillance Program is a collaborative effort between CAES (which traps and tests mosquitoes), the Department of Public Health and the University of Connecticut’s Department of Pathobiology in Storrs (which handle bird surveillance), and the Connecticut Departments of Public Health, Agriculture and Environmental Protection (which handle the human side of the equation). In 2003, more than 250,000 mosquitoes were collected, identified to species and tested as part of Connecticut’s surveillance program.
“The potential for exotic pests is higher now than it used to be because of the higher incidence of global trade,” said Academy member Louis Magnarelli, vice director of CAES and state entomologist. “We need to have surveillance in place. West Nile virus is widely established in our environment and it is likely to be around for quite a while.”
During peak WNV season, information from the surveillance program is relayed weekly to the State Health Department. “That information is used for weekly updates to the media and the general public,” Anderson said. “The citizens are getting the most current information possible so that they can take appropriate actions.”
“The number of human cases of West Nile virus in the state has increased steadily since 1999,” Andreadis said. In 2003, there were 17 confirmed cases of WNV in the state, two of which were acquired in Colorado. To date, there have been 41 human cases and one fatality in Connecticut, with the highest incidence of WNV in urban and suburban areas.
According to Anderson, a spike in WNV in Colorado in 2003 (2477 cases), has been at least partially attributed to a different species of Culex mosquito, Culex tarsalis, that readily feeds on humans. “We don’t have that species here,” he added.
Andreadis notes that while the risk of contracting WNV remains quite low, the disease itself is potentially serious. “Of every 150 people who are bit, only one will develop the virus and of those people who develop the virus only 20 percent will experience the most severe symptoms of meningitis and/or encephalitis. But, you don’t want to get this if you can avoid it,” he said.
Up to 50 percent of the patients who are diagnosed with severe cases of neuroinvasive disease, including meningitis and/or encephalitis, continue to have problems for up to a year. In even the mildest cases, known as West Nile fever, the virus can be debilitating with a 104-106 degree fever and severe headache.
According to Andreadis, the common school of thought is that WNV events will begin to taper off as more people, horses and birds are exposed to WNV and build up immunity. “To date, there is no indication of that happening,” he added. “It continues to be important for us to maintain the surveillance and trapping program, and for people in our state to continue to take precautions to guard against mosquito bites, especially in August and September. We have really not been successful in containing this virus . . . it all comes down to reducing individual contact with mosquitoes.”
The WNV has been detected in over-wintering Culex mosquitoes. “The mosquitoes feed on birds at the beginning of the summer and the virus builds up,” he said. “In crows, the virus levels in their blood are quite high and when a mosquito bites the bird, it picks up the West Nile virus. The mosquito then feeds a second time and inoculates the next host with the West Nile virus. That second host could be a bird, a horse or a human. Because crows are so susceptible to the virus, the continue to be our earliest indicator that the virus is around. The virus builds up in the bird/mosquito cycle during the course of the summer and we typically see cases in humans and horses in August and September. Humans and horses don’t serve as amplifying West Nile virus hosts because the levels of the virus in the blood remain relatively low.”
As the years go by, researchers are learning more about WNV. “We used to think that West Nile virus affected primarily the elderly, but now we are finding that all age groups, including children, are susceptible as well,” Andreadis said.
A vaccine currently exists for horses. A vaccine for humans is in clinical trials, but Andreadis estimates that a human vaccine is still two to three years away.
In addition to the surveillance program, researchers at CAES are monitoring any changes in the virus that might indicate a more virulent strain of WNV. “To date, the virus we are seeing is quite similar to the strains that were first identified,” Anderson said.
CAES scientists also are looking at ways to improve the surveillance program. “We are investigating different types of mosquito traps,” Anderson said. “We’ve found one trap that offers some advantages over the ones we currently use. It traps more mosquitoes and keeps the trapped mosquitoes in better condition. At the same time, these traps are not as mobile, so we are evaluating the pros and cons.”
CAES also is exploring different locations for the traps. “We’ve found significantly more Culex pipiens mosquitoes in traps located in tree canopies,” Anderson said. “The theory is that the mosquitoes are feeding on sleeping birds – crows and raptors, in particular, nest high in the trees. The tree canopy also offers conditions the Culex pipiens like in terms of temperature, humidity and light. So, it’s not necessarily a cause and effect situation – that the mosquitoes are up there because of the birds – but both are up there and the mosquitoes feed on the sleeping birds.”
Another good trap location has proven to be catch basins. “The mosquito breeds in catch basins,” said Magnarelli. “Even in dry years, there is an area of standing water below the pipe in a catch basin. The Culex pipiens mosquito likes that environment very much and feeds on organic matter in the catch basins. Without major rain storms to flush out the catch basins, they continue to breed there.”
“There are thousands of catch basins in major cities, so this may be a future opportunity,” Anderson said. “The only problem is that the current catch basin trap uses a battery that is strapped to the grate and a hazy light below to attract the mosquitoes. Since the events of 9/11, people are much more observant and when we used these traps in Stamford, several people reported them to the authorities as suspicious looking or possible bombs.”
CAES also is looking at biological control of mosquitoes. “In 2002, we worked with the towns of Stamford and Greenwich to evaluate the effectiveness of their truck-mounted spraying programs,” Anderson said. “We put mosquito traps out the night before spraying and counted the mosquitoes. A couple of days after they sprayed, we collected the traps and counted the mosquitoes. We found no difference in the number of mosquitoes, which led us to believe that the spraying was ineffective in curtailing the population.”
In a separate, but related, activity CAES placed laboratory-reared mosquitoes in cages throughout neighborhoods in Stamford. “The morning after they sprayed, there was one dead mosquito in all of our cages and it didn’t matter whether the cages were located in front yards or back yards,” Anderson said. “This validated our conclusion that the spraying was ineffective.”
CAES is currently working with the Connecticut Department of Environmental Protection to test the efficacy of spraying products and methods (trucks and other spraying mechanisms) at a field in Hammonasset State Park in Madison. “We are looking at various distances and quantities in an open field with no obstructions – no trees, no houses,” Anderson said. “In mosquito control, we’ve found that it’s important to think in terms of killing mosquitoes in the tree canopies as well as on the ground and we also need to think about killing the mosquitoes in the larval stage (primarily in catch basins).”
Connecticut universities including Yale University and the University of Connecticut also are carrying out WNV-related activities. “We are working on developing antibody tests with people at Yale,” Magnarelli said.
According to Magnarelli, CAES also is working in a joint effort with Yale University to evaluate the use of mice as a more specific indicator of WNV presence. “The crow is a good indicator of West Nile virus because the disease multiplies so well in their system and is fatal to the crow,” Magnarelli said. “However, because the crow flies around it may die on your street, but we can’t precisely pinpoint where it contracted the disease. Mice are more localized animals and don’t stray too far, so they might help us better pinpoint where the disease is contracted. Research in this area is still in the very early stages.”
As global trade increases, WNV isn’t the only concern, but Connecticut is on the watch. “In addition to our mosquito surveillance program, we are constantly flying over the state’s forests and conducting ground surveys to ensure that we are on the forefront of any changes that may indicate the presence of any new exotic pests of trees that might have entered our environment,” Magnarelli added. — Karen Cohen
[Karen Cohen is a freelance writer. She owns and operates The Write Stuff, LLC, in Hebron, CT.]
Additional resources on the web:
http://www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm (CDC)
http://dep.state.ct.us/mosquito/index.asp (State of Connecticut)
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