Eight minute listen
Highlights
- Chagas disease transmission in the United States is largely unknown and remains underreported.
- Researchers from the University of Florida Emerging Pathogens Institute and Texas A&M University collaborated on a 10-year study to investigate the ecology and risk of Chagas disease transmission in Florida.
- Published in PLOS Neglected Tropical Diseases, the study is the first to focus on the ecology of kissing bugs and their potential to spread the Chagas-causing parasite.
- The study demonstrates that kissing bugs readily invade human dwellings to feed on humans and companion animals.
- Researchers emphasize preventive measures, like managing wood piles near homes and increasing diagnostic screening for Chagas among clinicians.
Researchers from the University of Florida Emerging Pathogens Institute and Texas A&M University gathered their resources to investigate the potential of vector-borne transmission of Chagas in Florida. The 10-year-long study, published in the Public Library of Science Neglected Tropical Diseases, used data from Florida-based submissions, as well as field evidence collected from 23 counties across Florida.
Chagas disease is considered rare in the United States. Since it is not notifiable to most state health departments, it is quite difficult to know exactly how many cases there are and how frequently it’s transmitted.
Chagas disease is caused by the protozoan parasite Trypanosoma cruzi. Nuisance blood-sucking insects known as kissing bugs spread the parasite to humans when exposure to their feces penetrates the mucus membranes, breaches the skin or gets orally ingested. Interestingly, it is believed that most companion animals, like dogs and cats, acquire the parasite from eating the kissing bug itself.
The first record of kissing bugs, scientifically known as Triatoma sanguisuga, harboring T. cruzi in Florida was from an insect in Gainesville in 1988. However, kissing bugs have been calling the state home for far longer than humans have. Currently, there are two known endemic species of kissing bugs in the Sunshine State: Triatoma sanguisuga, the species invading homes, and the cryptic species Paratriatoma lecticularia, which live primarily in certain Floridan ecosystems but were not found in this study.
“We’ve done the groundwork to show that we have a vector in our state that is harboring a parasite, invading homes and feeding on humans and our pets,” said EPI member Norman L. Beatty, M.D. Since 2015, Beatty, the study’s co-first author, has dedicated his research program to the study of Chagas disease.
The study was a large collaborative effort using data submitted to UF researchers and the Texas A&M Kissing Bug Community Science Program. This program, ran by the Hamer Laboratory at Texas A&M, has been collecting community-donated insects since 2013, while Beatty and his team began their program in 2020. All the insects from this study were specimens from Florida collected using these mixed methods. When searching for bugs in the field, the team pulled out all the stops to ensure sample integrity.
Do the kissing bugs have ‘the bug’?
While mammalian infection, pest management strategies, disease screening and insect identification have all been previously studied, this is the first time that the relationship between infection rates and insects in human dwellings has been properly explored.
Together, the team sought to answer four key questions:
- Where are the kissing bugs?
- Are kissing bugs in our homes?
- What are kissing bugs eating?
- Do these kissing bugs carry the parasite T. cruzi?
The study collected insects in peridomestic environments, meaning insects that live in and around human dwellings. The researchers analyzed their stomach contents to determine the source of their last meal and whether the parasite was present. Of the insects collected, more than one-third were found inside homes.
“[Triatomine bugs] are ambush predators, right? They wait for you to relax and then suck blood,” noted EPI member Samantha Wisely, Ph.D.
They have been found to invade people’s homes like other pests and wait until their food source is sleeping. The disease earned its name as a silent killer because it can be latent in the body for decades; once it becomes chronic, it can attack the heart, brain and other organs with devastating results.
From 2013 to 2023, the team studied samples of over 300 insects across Florida. The team surveyed four additional locations in southern Florida, but to no avail. They were perplexed as to why no bugs were found in southern Florida, indicating more research needs to be done in the future. The parasite T. cruzi was found in 29.5% of the tested triatomines, with infections detected in 12 of the 23 Florida counties. It is irrefutable — all the necessary ingredients for vector-borne and possible oral transmission routes of Chagas disease are present in Florida.
When kissing bugs come to dinner: Analyzing their last meal
As UF faculty member Nathan Burkett-Cadena, Ph.D., was engrossed in research on mosquito, black fly and no-see-um-transmitted pathogens, Wisely and Beatty were looking for someone who could analyze the stomach contents of the kissing bugs Beatty had been collecting. Burkett-Cadena is an associate professor at the UF/IFAS Florida Medical Entomology Laboratory. He studies diseases spread by true flies but was recruited by Beatty for his knowledge in bloodmeal analysis.
“Sam [Wisely] said [to Beatty], ‘Hey, you know Nathan could do blood meal analysis on these,’ and I said, ‘Yeah, send me some of your samples, and we’ll see what we find,’” Burkett-Cadena said.
They expected to find these insects primarily feeding on wild and domestic mammals — and maybe sometimes on people. To their surprise, they discovered that most kissing bugs found in the home had been feeding on humans, contrary to those discovered outside the home, which primarily contained blood from expected sources like mammals, amphibians and reptiles. This suggests that kissing bugs readily enter the home to bite humans, proving a crucial need for preventative measures to safeguard residences from Chagas disease.
Chagas is in our backyards — literally
When looking at where kissing bugs call home, our homes are a great start. These insects live in the wild, but when opportunity knocks, they tend to answer. Living near human dwellings likely guarantees shelter and a food source for triatomines.
Wisely’s research on how human impacts on the landscape alter ecosystem function made her a no-brainer addition to Beatty’s research initiative. The Wisely Lab conducted nearly all the molecular genetic testing for Trypanosoma cruzi in the insects gathered by Beatty and Chanakya R. Bhosale, co-first author and undergraduate researcher in Wisely’s lab at the UF/IFAS Department of Wildlife Ecology and Conservation. Understanding the ecology of triatomines was essential to answering the question, “Why are kissing bugs invading homes?” As Florida’s population grows, more land is required for housing.
“I think that where we have seen transmission occurring in and around homes is in this, what I would call, peri-urban setting,” said Wisely, a professor at the UF College of Agricultural and Life Sciences. “So, it’s not quite suburbs, it’s not quite rural … we’re building into the Trypanosoma cruzi habitat, and so I think it increases the likelihood of people and companion animals becoming infected.”
Most Floridians would tell you it’s common knowledge not to have standing water near your home. Mosquitos use standing water reservoirs to lay their eggs, and their breeding season aligns with the study’s findings on kissing bug seasonality. The researchers aim to create the same level of awareness around kissing bug habitats near a home. Where Floridians associate standing water with mosquitoes, the goal is to associate kissing bugs with wood piles, the insect’s version of home-sweet-home.
“Don’t keep those wood piles right next to your house. Don’t keep them right next to where your dog sleeps, I think that’s a huge part of it,” Wisely said. “That’s the integrated part, not just using pesticides and insecticides. … Habitat management, as well as changing your behavior.”
When collaboration bites back at disease
Of the insects gathered, almost half were donated by community scientists. The researchers described community involvement within studies as invaluable to expediting and broadening research. This approach not only epitomizes One Health science and the collaborative spirit of the EPI, but also speaks to the importance of multidisciplinary science.
“Well, you can’t do the study without it, for sure. So, it is — I’m going to try and think of the most important adjective I can — critical, pivotal. It is absolutely essential to doing this kind of work,” Burkett-Cadena said.
Moving forward, the team hopes this study can bring awareness to the present risk of Chagas disease transmission in Florida. Screening for Chagas is as simple as testing for a tick-borne disease. With this new information, clinicians and primary care providers can now add Chagas diagnostics to their arsenal against neglected tropical diseases in the Sunshine State.
“When I transitioned from [the] University of Arizona to start my faculty position at UF College of Medicine, my objective was clear to me: create a multidisciplinary, collaborative team, and dive into Chagas taking a One Health approach,” said Beatty, who is currently an associate professor. “This project is only the beginning to our investigation into Chagas here in Florida. Our multidisciplinary approach to tackling a neglected tropical disease really bodes to the culture of ‘team science’ we promote here at UF.”
Written by: Sydney Burge