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Justin Harbison doesn’t know—or won’t admit—how he got the nickname “Sewer Monster.” “I like to think I didn’t name myself,” he joked. “I’m Gen X. It’s a comic book sort of thing.”
However the nickname arose, and it’s fitting for Harbison, an associate professor in the Parkinson School of Health Sciences and Public Health at Loyola University Chicago who works with four mosquito abatement districts in the Cook County suburbs to reduce the spread of mosquito-borne diseases by treating the standing water inside stormwater catch basins.
In Chicago and other U.S. cities, Culex pipiens, or Northern House Mosquitoes, which can carry West Nile virus, like to lay their eggs in the sludgy runoff that collects in the sewer inlets. “West Nile virus is really our big thing,” Harbison said. “Overwhelmingly, the most common source of the West Nile-carrying mosquitoes is right here in these catch basins.”
Near the curb of a quiet street in Des Plaines, Illinois, he lowered a long rod attached to a cup into an open catch basin. When he pulled it out, the water-filled cup was teeming with swimming mosquito larvae but contained only a few floating pupae—a good sign.
Earlier in the summer, the North Shore Mosquito Abatement District treated the catch basin with pyriproxyfen, a growth-regulating insecticide that prevents larvae from developing into pupae and hatching into flying adult mosquitoes. The presence of just a few pupae suggested the larvicide was working.
“We’re trying to make people’s lives better,” he said. “The more we look into these treatments, the more validated we feel because our work is actually making a difference that we can detect pretty easily now. Recently, we’ve seen that if you treat these basins with a highly effective product, you can actually see a decrease in human West Nile virus cases.”
Others might blanch at the sight of mosquito larvae wriggling in sewer broth, but not Harbison, who relishes being outdoors, getting his hands dirty, and above all, protecting public health.
As a child of the ’80s, Harbison dressed up as a “bug buster,” a sartorial riff on the hit movie Ghostbusters. Years later, as an entomologist at the Palo Verde National Park in Costa Rica, he became fascinated with mosquitoes, the world’s deadliest animal and a leading vector of lethal diseases, such as malaria, dengue, and West Nile virus.
“Every year, mosquitoes kill more people than people kill people,” Harbison said. “And the best way to combat that is through investment in public health.”
Since appearing in the United States in 1999, West Nile virus (WNV) has become the country’s leading cause of mosquito-borne disease. Last year in Illinois, according to the Illinois Department of Public Health, there were 50 confirmed cases, with 10 resulting in death; 34 of these cases, including two deaths, were in Chicago. Most infected people do not feel sick, but about 20 percent develop a fever or flu-like symptoms, and fewer than 1 percent develop severe, potentially fatal, neuroinvasive diseases, such as encephalitis or meningitis, according to the Centers for Disease Control and Prevention (CDC). People over 65 years old or those with compromised immune systems are most at risk for developing serious illnesses. However, anyone who lives or travels where the virus circulates is at risk of infection, and there is no licensed vaccine to prevent West Nile virus.
The CDC’s advice? Avoid getting bitten.
Today, Harbison sits on the board of the North Shore Mosquito Abatement District and works closely with Patrick Irwin, the agency’s assistant director, to help people do that. The two test treatment sites, co-author scientific papers, educate the public about risk factors, and find ways to amuse each other while working to combat disease-carrying mosquitoes.
“We have a lot of colleagues throughout the United States,” Irwin said. “Justin is everyone’s favorite. In our field, he’s a big deal. He’s a really big deal.”
Why catch basins?
While mosquitoes breed in lakes, ponds, and other water sources on private and public lands, many of these hold water continuously, making them hospitable to mosquito-killing predators, like birds, bats, and fish.
Catch basins, though, are protected by sewer grates and flushed out as stormwater filters into underground sewer tunnels. They’re also littered with decaying leaves, salt, and roadway debris repellent to other animals. But Culex mosquitoes seem to prefer them.
“Culex mosquitoes love to develop in disgusting water,” Irwin said. “It’s probably an evolutionary trait because you’re not going to have predators, you’re not going to have fish down there, you’re not going to have dragonflies, you’re not going to have anything. So they’re pretty safe.”
In the warm months when mosquitoes are active—typically from June to September—the North Shore agency introduces and monitors nontoxic larvicide treatments at some 80,000 catch basins across a nearly 250-square-mile region in Cook County’s north suburbs and parts of southern Lake County.
The agency also monitors 40 adult mosquito traps across the district to track the movement and disease status of mosquito populations, which can contract the West Nile virus when feeding on birds. The integrated approach limits the need for airborne pesticide sprays, which can drift onto flowering plants and harm pollinators like bees and butterflies that support ecosystem health.
“It’s basically the most environmentally friendly and efficacious way of getting rid of mosquitoes,” Irwin said.
Every year, mosquitoes kill more people than people kill people. And the best way to combat that is through investment in public health.
— Justin Harbison, associate professor
West Nile virus and climate change
Hotter, drier summers as result of climate change appear to be extending the length of the mosquito season—the North Shore district now finds adult mosquitos from March to October— and making conditions more tolerable for invasive species like the aggressive Asian tiger mosquito, or Aedes albopictus, that likes to dwell near homes and bite during the day.
The changing climate also appears to be increasing the risk of West Nile transmission in Upper Midwest cities like Chicago.
“It’s kind of counterintuitive,” Harbison said. “With drought, we tend to expect West Nile virus to be worse. And one of the reasons we think this is, is because catch basins play a bigger role. If it’s rainy, you’ve got the Forest Preserves of Cook County and all the standing water out there. But when it’s dry, pretty much the only standing water habitat that we can find is in these basins.”
While the presence of more bloodsucking Culex mosquitoes is exciting to no one, it’s yet another reason why the larvicide treatments are so crucial to protect public health. By treating catch basins, Harbison estimates government agencies can reduce mosquito populations by more than 35 percent, a figure extrapolated from a study of larvicide treatments he and other researchers conducted in 2019 in metropolitan Milwaukee.
“That’s probably enough to reduce human risk just at that level,” he said. “And I think we’ve gotten better than that now with the product we’re using now.”
“It’s straight-up public health,” Irwin added. “I mean, medical doctors are great, but they do one patient at a time. What we do is one population at a time.”
Tips to stay safe
Dump any standing water. If water stands for five days, it can attract egg-laying mosquitoes. Remove water from buckets, flowerpots, and other containers that hold rainwater to prevent them from populating.
If you’re going to a natural area, use a government-registered repellent. Harbison suggests repellents with 30% of the chemical DEET or other vetted ingredients, such as picaridin or lemon eucalyptus oil.
When hanging out outside, use a box fan or oscillating stand fan to create an artificial breeze. Mosquitoes are poor flyers when it’s windy, and the draft will encourage them to relocate. It will also help disperse carbon dioxide and chemicals in sweat that attract mosquitoes.
Read more stories from the Parkinson School of Health Sciences and Public Health.
