Kissing bug. Cone-nosed bug. Vinchuca. Chipo. Barbeiro.
These English, Spanish, and Portuguese names are local sobriquets for nocturnal, blood-sucking insects that transmit a zoonotic parasite native to Latin America. In recent years, Trypanosoma cruzi‘s slow, insidious assault on human hearts and intestines, commonly called Chagas disease (CD), has also surfaced in the Latinx diaspora. For example, experts estimate that here in the U.S., between 240,000 and 350,000 people are currently infected with T. cruzi.
But what about the bugs themselves? Are the odd, inquisitive insects bearing deadly cargo also on the move — or have they always lurked in North America hidden in plain sight?
According to Norman Beatty, MD, an infectious diseases specialist at the University of Florida who first studied T. cruzi vectors in the southwestern U.S., there’s no easy answer to this question. Today, however, 10 kissing bug species that can carry T. cruzi live in 29 states in the southern half of the U.S. What does this mean? Are humans and animals now contracting this “traditional” Latin American blight here at home? Although accurate case counts are hard to come by because so many people are either undiagnosed or silently infected, the answer is most likely: yes.
For more insights on kissing bugs’ North American hide-outs and hosts, consider recent data from Florida presented in November 2022 at the 71st annual meeting of the American Society of Tropical Medicine and Hygiene. This statewide study conducted by Beatty and colleagues at the University of Florida and Texas A & M University between 2013 and 2022 used “community science” (an approach that allows local residents to assist in collecting specimens) to assess kissing bugs from 22 counties. All of the 298 triatomine vectors captured in and near human dwellings were Triatoma sanguisuga (the most common peri-domestic vector east of the Mississippi in the U.S.), and roughly 30% harbored parasites, which cause the disease in humans.
In addition, prior to their capture, work by Nathan Burkett-Cadena, PhD, at the Florida Medical Entomology Laboratory showed that the infected bugs had siphoned blood from a wide array of animals, from humans to wild and domestic mammals to reptiles and amphibians. In short, at least in Florida, T. cruzi inhabits many creatures, which tells us it already has a large zoonotic reservoir.
Recent Shifts in Chagas Disease
In 1998, when I published a story in Discover magazine about a Mexican-American immigrant with end-stage Chagas cardiomyopathy who declined a cardiac transplant that might have saved his life, the global prevalence of T. cruzi-infected people was roughly 15 million. Today, that estimate has fallen by more than 50%. Nonetheless, one thing hasn’t changed. Wherever they live, the vast majority of infected human hosts still don’t know they harbor a ticking protozoan time-bomb (as it can take years to decades to clinically manifest) that confers a 1 in 3 chance of robbing them of their health and shortening their life.
The good news? Recent years have seen more research on new diagnostics and drugs, as well as advocacy for expanded screening of people who might benefit from benznidazole or nifurtimox — two currently-available drugs that can prevent CD in certain people, especially newly-infected or younger-aged patients.
On the other hand, identifying or training medical professionals qualified to give these drugs remains a challenge.
How Much Autochthonous Disease Is There?
In 2020, Beatty and a colleague from Arizona published a provocative article entitled “Autochthonous Chagas Disease in the United States: How Are People Getting Infected?” referencing nearly 100 T. cruzi infections contracted in Arizona, Arkansas, California, Louisiana, Mississippi, Missouri, Tennessee, and Texas, among other states. Newer modeling suggests that the U.S. could have as many as 10,000 people who acquired their infections within our borders. But leaving aside the exact number, the question of how these people got infected is equally germane.
While accepting that some autochthonous U.S. infections are acquired by the classic route (through a kissing bug’s post-blood meal fecal contamination of a bite or mucous membrane), Beatty’s paper also details different “defecation behaviors” in North versus Latin American kissing bugs. Such observations open the door to yet another mode of transmission: inadvertent ingestion of food or drink contaminated by bugs or their feces. It’s hardly improbable. Not only have food-borne CD outbreaks occurred in humans in Latin America, oral ingestion of bugs can also lead to T. cruzi infections in dogs.
If you’re like me, knowing that the U.S. has many undiagnosed CD patients raises one set of imperatives. In addition, knowing that domestic vectors are infecting U.S. residents poses a second mandate. So, here’s what I’d like to see happen over the next 5 years.
First, I believe we need more community education around Chagas disease, especially for those whose geographic location, housing, or lifestyle increases their risk of exposure. One place to start? School-based programs paired with community science.
Secondly, even though U.S. blood banks began testing for T. cruzi in 2007, many clinicians — both in primary care and relevant specialties like cardiology and obstetrics — fail to test certain high-risk individuals. Routine serological screening of high-risk women of child-bearing age in particular could conceivably prevent 100 or more congenital infections per year. A strategic effort to educate multiple providers is long overdue.
A third priority endorsed by experts is to standardize national practices around pre-transplant testing of organ donors and recipients, since organ-related transmission of T. cruzi as well as reactivated disease in immunosuppressed hosts is one more modern twist on the ancient foe.
In short, continued surveillance for infected bugs in the U.S. combined with better education, screening of patients, and access to qualified care are all needed to address 21st century issues around imported and autochthonous disease. Norm Beatty left me with these final thoughts: “Why is Chagas not a reportable infectious disease in all 48 states in the continental U.S.? Why do we not have federally mandated funding and resources for people living with Chagas disease? With earlier intervention, including testing and anti-parasitic medication, we can help our patients live better, healthier lives.”
Claire Panosian Dunavan, MD, is a professor of medicine and infectious diseases at the David Geffen School of Medicine at UCLA and a past-president of the American Society of Tropical Medicine and Hygiene. You can read more of her writing in the “Of Parasites and Plagues” column.