Highlights
- Chagas is a poorly understood and potentially lethal disease. In the U.S., it primarily affects people who have immigrated from Latin America, but researchers are discovering locally acquired cases in multiple states.
- Chagas is caused by a parasite spread primarily through the feces of kissing bugs, nuisance blood-sucking insects that can invade our homes.
- Many people with Chagas are unaware they have the disease. Once Chagas becomes chronic, it can attack the heart, brain and other parts of the body with devastating results.
- University of Florida researchers are screening people most at risk of Chagas in Florida to uncover undiagnosed cases.
- Nearly 30% of Florida kissing bugs tested by UF researchers carry the parasite that causes Chagas disease. More than 50% of Florida opossums and about 40% of raccoons tested by the team also have the parasite, suggesting they, too, may play a role in the disease’s transmission.
When Norman Beatty first witnessed people sleeping under mosquito nets in rural Arizona, he was stunned. And yet, some residents of remote areas in the U.S., including parts of Florida, use the nets in their homes each night – not to protect against mosquitoes, but kissing bugs, blood-sucking insects that can spread a potentially lethal disease known as Chagas.
Those nets were a catalyst for Beatty, M.D., an assistant professor of medicine in the University of Florida’s Division of Infectious Diseases and Global Medicine and a member of the Emerging Pathogens Institute. Since 2015, Beatty has dedicated his research program to the study of Chagas, a little-known illness caused by a microscopic parasite called Trypanosoma cruzi, passed primarily via the feces of infected kissing bugs.
Chagas disease can be a silent killer: Symptoms may take decades to appear and are often irreversible once they are recognized. Most people infected with T. cruzi do not know they carry the parasite, Beatty said. Without treatment, they can remain infected for life. About one-third will develop chronic Chagas, which can attack the heart, brain and gastrointestinal and peripheral systems with fatal results.
An estimated 300,000 people are living with Chagas disease in the U.S., but fewer than 1% have been diagnosed. Florida, home to both the kissing bug and T. cruzi, is thought to have the third-highest number of people living with chronic Chagas, behind California and Texas. But the disease remains poorly studied in the state and globally.
“Chagas truly is a neglected tropical disease,” said Beatty. “A tremendous amount of work needs to be done to understand this parasite and how it’s affecting human beings.”
Chagas is also a disease of inequity, he said. In the U.S., it disproportionately affects people who have immigrated from Latin America, where the parasite is more common, and those exposed to kissing bugs in rural areas. These groups also tend to have limited access to healthcare.
As part of a three-year investigation, Beatty and UF/IFAS collaborators Samantha Wisely, Nathan Burkett-Cadena and John Diaz, as well as Colin Forsyth from the Drugs for Neglected Diseases initiative and Eva Novakova from the University of South Bohemia, have been working with urgency to track and diagnose the disease in Florida and investigate the ways in which T. cruzi spreads.
“It’s important that we try to reach all the populations at risk for Chagas,” Beatty said. “Without access to resources, patients will continue to manifest the chronic disease state and may die from this infection without ever knowing they had this disease.”
Rapid screening unearths Florida’s undiagnosed Chagas cases
Little is known about the prevalence of Chagas in Florida. It is not a reportable disease to Florida’s Department of Health, meaning that the state is not monitoring its occurrence, and researchers are unable to track infections via routine blood and organ donor screening. Many healthcare providers aren’t even aware Chagas is in Florida, and testing can be limited, Beatty said.
To help close the gap, Beatty and his colleagues have established a screening program in clinics and hospitals, including UF Health, targeting people with the highest risk of infection. His research suggests that using two rapid blood tests simultaneously could be a swift, simple way of diagnosing the disease, a boon in rural areas that lack laboratories.
Time is of the essence: When detected early enough, T. cruzi infections can be treated with antiparasitic medications. The sooner a patient receives therapy, the less chance the disease will progress to a chronic stage.
“What we want to do is unearth undiagnosed cases of Chagas disease,” Beatty said. “People with a chronic infection should be under the care of a physician to help manage this disease before it becomes potentially fatal.”
Thus far, the team has screened approximately 700 people, with about 1% testing positive for Chagas. Beatty estimates about 18,000 to 20,000 people in the state live with the disease.
He has also begun testing Latin American patients at UF Health who have heart abnormalities that can’t be attributed to blocked arteries or a heart attack. In parts of Latin America, Chagas disease is the most common cause of heart failure in the absence of coronary artery disease. Chagas can trigger heart failure regardless of a patient’s age or other health factors.
A key research question is determining which patients are most likely to develop the chronic form of the disease. Beatty said multiple factors are likely at play, including immune response, genetic predisposition and the parasite’s intracellular infection.
“This parasite is able to survive many decades inside of a human cell and hijack its machinery. It is likely this molecular hijacking that triggers chronic fibrosis and inflammation, which weakens the heart over time,” he said.
As an infectious disease doctor, Beatty also treats patients living with human immunodeficiency virus, and he said he sees parallels between HIV and Chagas. Both are infectious diseases that can take decades to appear in the chronic – and ultimately fatal – state. But researchers are “light years behind in our knowledge and abilities to manage patients with Chagas diseases compared to HIV,” he said.
Kissing bugs are invading Florida homes
The majority of people with Chagas disease acquired the parasite in Latin America, Beatty said. But T. cruzi and kissing bugs are also present in the U.S., suggesting there are routes of disease transmission closer to home. Eleven species of kissing bugs, also called triatomines, live in the U.S., four of which commonly invade houses and bite humans. One of these species, Triatoma sanguisuga, is a known vector of Chagas and lives in Florida. Beatty and his collaborators have found T. sanguisuga in Florida homes and documented the bug biting humans and pets.
Very little is known about kissing bugs compared with other arthropods that vector disease, such as ticks and mosquitoes. Like bedbugs, kissing bugs typically take a blood meal at night while their hosts are sleeping.
Most people won’t immediately feel the bite of a kissing bug, due to anesthetic-like molecules injected by the insect, but the bite usually leaves an itchy, red welt behind. Allergic reactions to kissing bug bites are common, and anaphylaxis has resulted in at least one documented death in Arizona, Beatty said.
While kissing bugs prefer to feed on people and other mammals such as dogs and opossums, they’re not picky eaters. In Florida, kissing bugs also feed on reptiles, amphibians and even other insects, according to a forthcoming study by Beatty, Wisely, Burkett-Cadena and Sarah Hamer and Gabe Hamer of Texas A&M University.
Nearly 30% of kissing bugs tested by the team carried the T. cruzi parasite.
“This is important research here at the University of Florida that helps us understand the diversity of our kissing bugs and their blood meals,” Beatty said. “T. cruzi was commonly found among our bugs, and these bugs really are biting humans and invading their homes.”
A crucial difference between Chagas disease and other illnesses vectored by arthropods is that the pathogen is not transferred during a bite, but through fecal material. Kissing bugs can defecate on hosts while feeding or elsewhere in the home. Some people have acquired Chagas from food contaminated by the bugs’ feces.
Beatty suspects that some people living with Chagas in Florida became infected with T. cruzi locally, rather than abroad.
“There are vulnerable populations in the state of Florida who are exposed to these bugs,” he said. “There’s a lack of awareness that this is truly a problem.”
Infected opossums add to complexity of Chagas
Kissing bugs aren’t the only organisms capable of spreading the T. cruzi parasite. Infected humans and other mammals can transmit the parasite to their offspring, and the parasite can be passed through blood and organ donations.
Beatty, Wisely and Burkett-Cadena have also pinpointed Florida’s opossums as possible spreaders of T. cruzi. The opossum, Didelphis virginiana, is one of 27 mammal species in the U.S. known to serve as a reservoir host for the parasite, suggesting that Chagas may be a zoonotic disease as well as a vector-borne one.
A 2022 study led by UF/IFAS graduate student Carson Torhost showed that more than half of Florida opossums trapped and tested by researchers carried the parasite in their blood, feces and/or anal gland secretions. Opossums spray these secretions into the environment where they could contaminate crops and garden vegetables or other surfaces with which people could come into contact.
“Basically, we found that Florida opossums are wildly infected with Trypanosoma cruzi,” Beatty said. “There are other sources of infection that haven’t been described well yet, and my impression is that the opossum is a part of that story.”
A recent study from the team found that raccoons, Procyon lotor, are also key reservoirs of T. cruzi. About 40% of Florida raccoons tested by the researchers were infected with the parasite.
The complexity of Chagas – and the dearth of research on the disease – provides continual fuel for Beatty’s curiosity.
“From a One Health paradigm, Chagas is a great model for tackling neglected tropical diseases,” he said. “In life, you find certain ways that you can truly make a difference. This is a worthwhile cause that will take a lot of effort, but, for me, it’s worth tackling.”
Wisely is a professor in the UF/IFAS Wildlife Ecology and Conservation Department. Burkett-Cadena is an associate professor in the UF/IFAS Florida Medical Entomology Laboratory.
Diaz is an associate professor in the UF/IFAS Agricultural Education and Communication Department.
UF’s Chagas research is supported in part by Mundo Sano and the Drugs for Neglected Diseases initiative (DNDi).
Written by: Natalie van Hoose