While their adorable name stems from the way they leave midnight nips and smooches around human mouths and eyes, kissing bugs actually pose the greatest threat to humans through their feces. After locking lips with their sleeping victims, these inch-long insects take a dainty dump at the scene of the crime. And this repulsive encounter is worse than unhygienic: those feces spread microscopic parasites that cause Chagas disease.
Fortunately, scientists at Texas A&M University have a new weapon against these and other disease-carrying insects. As they report today in the Journal of Medical Entomology, the movements of elusive kissing bugs can now be tracked with radio transmitters, potentially equipping researchers with new, cost-effective tools to stop the spread of insect-borne illness.
Chagas disease is most prevalent in Central and South America, where it currently afflicts up to 8 million people. But it's also been increasingly identified in the southern United States: In Texas, 50 percent of captured kissing bugs test positive for parasites that spread the disease, and up to a million Americans may currently be suffering from Chagas. “In the U.S. up until now, kissing bugs and Chagas disease have been somewhat neglected and underreported,” says the study’s lead author Gabriel Hamer, an entomologist at Texas A&M University. “In recent years, this is changing and the medical community and general public are increasing the recognition that kissing bugs are indeed in the U.S.”
When kissing bugs take blood meals from infected individuals, they ferry the disease-causing parasites to their next victims. Because of this—and because Chagas cannot be transmitted directly from person to person—knowing the movements of kissing bugs is critical to stopping the spread of disease. (Many of those infected remain asymptomatic and unknowingly harbor the disease, but carriers can still transmit parasites if bitten again. Animals, including pets, are also vulnerable to infection, putting their owners at additional risk if they are bitten by another kissing bug.)
If kissing bug feces are rubbed into the mouth, eyes or any break in the skin—including the bug’s recent bite mark—parasites can enter the body and spread quickly through the tissues and blood. The disease causes a mild fever-like syndrome that can permanently compromise organ function if left untreated.
Controlling kissing bug populations is considered the most effective method for preventing Chagas disease, which is considered a neglected tropical disease and accrues around $270 million in medical costs each year. While the insects are susceptible to insecticides and flummoxed in the face of netting, their diminutive size, nocturnal habits and neutral coloring make them difficult to spot. Little is known about their movements and dispersal, but what we do know is this: They thrive best in the nooks and crannies of older, poorly-constructed buildings—which are common in the countries where Chagas runs rampant.
For entomologists, kissing bugs pose another challenge: Their populations can be sparse, particularly in the U.S. Their solitary, agoraphobic lifestyle makes them frustratingly difficult to track by conventional methods, such as tag-and-release studies common in other insects.
To uncover the day-to-day movements of kissing bugs, a team led by Gabriel Hamer and veterinary ecologist Sarah Hamer of Texas A&M University chose an unconventional technique, leveraging cutting-edge radio telemetry technology to track the bug’s locations. The pair, who are married, then teamed up with Texas homeowners currently battling kissing bug infestations to conduct their fieldwork. They chose three private residences spanning diverse landscapes, allowing the team to study two different species of kissing bugs.
After capturing a handful of kissing bugs at each residence, the researchers affixed tiny transmitters to the insects’ backs with superglue. The transmitters sent radio signals reporting the bugs’ location back to the team’s receivers, enabling the researchers to spy on the insects’ shenanigans remotely.
“This technology makes it possible to track the kissing bugs in a way that’s not possible visually,” says Matthew Siderhurst, an entomologist at Eastern Mennonite University who also employs radio telemetry in his work, but was not affiliated with the study. “This is a way to answer a lot questions… like, ‘what is the insect doing when we’re not watching?’”
The Hamers monitored a total of 18 movements in 11 kissing bugs. Under radio surveillance, the bugs were fairly inactive, scuttling an average of only 12.5 feet at a time. Additionally, the nocturnal insects tended to return to consistent hovels to rest and relax during the day.
At one of their experimental sites, the researchers collaborated with homeowners who had previously lost several dogs to Chagas disease. To protect themselves and their pets, the Texas residents had begun actively removing kissing bugs from the property, amassing hundreds of insects for Hamer’s research over the course of four years.
The utility of the radio transmitters shone through when it revealed a female kissing bug had nestled into a small crack between the top and bottom halves of a plastic doghouse—a location revealed only by dismantling the structure. “It’s something we would have been missed through routine cleaning and spraying,” explains senior author Sarah Hamer. “If we know about these places, we can pay attention. But otherwise we don’t think twice about it.”
Radio telemetry has been used successfully to track large wildlife for decades. Recent technological advances, including compaction of transmitters, have even enabled its use with insects in the context of pollination, crop pests and conservation. But the Hamers’ work is the first to deploy the technology to track insect vectors of disease. These early successes may pave the way for tracking kissing bugs on a more global scale.
There are drawbacks: bug-sized transmitters have weak ranges and short battery lives, limiting each tracker’s range to a maximum of two weeks and 300 feet. And even at 0.2 grams, each transmitter weighs about as much as an individual kissing bug. But Sarah Hamer knew that kissing bugs were no strangers to weight fluctuations, as even an average blood meal can also double their load. Next, she and her team will test whether bearing the transmitter has a negative impact on the bugs’ behavior.
Sarah Hamer, who has previously worked extensively with radio telemetry in birds and mammals, hopes the technology will continue to advance with the times. “Years ago, I was working with transmitters that weighed two grams, which was cutting edge at the time,” she says. “The ones we used with the kissing bugs are one-tenth of that. We were pushing the limits with birds, and now we’re down to insects.”
For now, the radio transmitters have already vastly expanded the options for infectious disease specialists and entomologists hoping to gain insight into the covert lives of kissing bugs. In their fieldwork, Hamer and her colleagues found that all the specimens they’d tagged at one residence had died, unexpected revealing the effectiveness of insecticide treatment conducted by a pest management company a few months prior. This opens the door to testing the potency of different chemicals against these insects—an especially relevant issue in the U.S., where there is currently no insecticide specifically labeled for use against kissing bugs.
What’s more, through their work with private citizens of Texas, the researchers hope to continue to engage public interest in Chagas disease prevention. “We’re empowering these citizen scientists,” Sarah Hamer says. Homeowners like those who participated in this study are some of the Hamers’ most important sources of wild kissing bugs, and will continue to provide specimens for future work.
For diseases like Chagas that exist at the human-wildlife interface, knowing the risks and vulnerabilities on both sides is critical. Modern technology now enjoys an increasing role in stopping the spread of infectious disease—and in the future, these tracking tools will reveal far more than whom bugs are smooching on the sly.