Bugging bugs to understand Chagas disease
The carriers of a nasty illness are almost impossible to find – until they bite you. Jeff Glorfeld reports.
Scientists in the United States are attaching miniature radio transmitters to the backs of blood-sucking insects known as kissing bugs, in an effort to learn more about the disease-carrying creatures.
Researchers in Texas glued transmitters weighing 200 milligrams to different species of kissing bugs, also known as triatomine bugs, so they could track their movements. The insects, from the family Reduviidae, typically move at night and hide during day, and uncovering their movements could help reduce their impact as disease carriers.
In a report published in the Journal of Medical Entomology, lead author Gabriel Hamer, from Texas A&M University, says: "While studying kissing bugs in Texas, we have been perplexed regarding their movement behaviour.”
Hamer says during their research, he and his colleagues observed dozens of kissing bugs emerging simultaneously from natural habitat and arriving at people’s homes.
“Where are they coming from?” he says. “How far are they travelling? Why are they dispersing? These observations and others provided the motivation to try to utilise a methodology to track wild kissing bugs and study movement.”
A 2015 report by broadcaster CNN into the insects says the nocturnal, 2.5-centimetre-long bugs are nicknamed kissing bugs because they feeds on mammals' blood, and particularly like to bite near the lips and eyes of animals, including humans, while they sleep.
The bites can turn deadly when bugs infected with the parasite Trypanosoma cruzi defecate and the faecal matter infects the bite. The infection is known as Chagas disease.
Hamer and colleagues worked with three families who had routinely found kissing bugs around their homes. The researchers tagged and tracked 11 of the insects, and painted the transmitters with fluorescent paint to aid in rediscovery.
Over 12 days, the researchers found the insects walked on average about three metres, up to a maximum of about 20.
One particular kissing bug revealed just how elusive they can be. It was initially captured near a dog kennel and was found the next day in a small slit where the top and bottom of the plastic kennel fitted together.
“This would have been a very difficult location to find without the use of radio telemetry,” Hamer says.
“The owner, who has lost several dogs to canine Chagas disease, regularly removes kissing bugs from inside and under the kennels, but any kissing bugs in the cryptic hiding location in the joint of the doghouse would have been missed.”
According to the US Centres for Disease Control and Prevention (CDC), Chagas disease – first described in 1909 by Brazilian doctor Carlos Chagas – is transmitted to animals and people by insects that are found only in the Americas, mainly in rural areas of Latin America where poverty is widespread.
The CDC estimates about eight million people in Mexico, Central and South America have the disease, most of whom do not know they are infected. If untreated, infection is lifelong and can be life-threatening.
The CNN report says there are about 300,000 cases of Chagas in the US but most of those were contracted in other countries. Nevertheless, species have been detected in 28 states, with more than 50% carrying Trypanosoma cruzi.
The new study marks an initial foray into tracking triatomines via radio telemetry, but it could open the door for more in-depth studies into kissing bugs' movements. Hamer says he is eager to continue this research and hopes other entomologists and vector-management researchers will take advantage of advances in radio telemetry to track insect behaviour.
“Kissing bug dispersal and movement behaviour is fundamentally involved in the exposure of dogs and humans to the agent of Chagas disease,” he says. “We hope our research can continue to make advancements in our understanding of this kind of basic biology of the insect vector that will improve our ability to intervene and minimise Chagas disease.”