THE PARASITE CAN LIVE IN THE
BODY THROUGHOUT A PERSON’S
LIFE WITHOUT CAUSING SYMPTOMS,
BUT 20 TO 30 PERCENT OF
INFECTED PEOPLE WILL SUFFER
CARDIAC DAMAGE.In the United States, transmission
of the deadly Trypanosoma
cruzi parasite to humans is rare,
but dogs appear to be more
vulnerable. A recent study tested
for Chagas disease among dogs
that U.S. agencies use in tasks
such as sniffing for explosives or
helping with search-and-rescue
operations. Though the dogs
showed no signs of being sick,
more than 7 percent of those
tested were infected. “When we
take a look at their hearts, then
we see signs of heart disease,” says
study director Sarah Hamer, an
associate professor at Texas A&M
University’s College of Veterinary
Medicine and Biomedical Science.
Similar rates of infection have
been found among dogs in Texas
animal shelters. Scientists say
dogs might be more at risk for
the disease than people because
dogs may eat bugs that carry the
parasite. However, they say, the
risk of infection passing from dogs
to humans is extremely low. —DH
Another target
of the bug’s bite
Some 10,000 people die each year from Chagas
disease. The Centers for Disease Control and Pre-
vention (CDC) estimates that about 300,000 people
living in the United States have the disease. Many,
like my auntie, grew up in poor communities in South
America, Central America, or Mexico. Few know they
have Chagas disease because the parasite that causes
it, Trypanosoma cruzi, is a cunning microorganism.
It’s transmitted to people by way of a triatomine
insect called a kissing bug. In the acute stage, peo-
ple usually can be cured; unfortunately, less than
one percent of infected people are diagnosed or
treated. The parasite can live in the body throughout
a person’s life without causing symptoms, but 20
to 30 percent of infected people will suffer cardiac
damage. Chagas-related heart problems include
irregular heartbeats, left ventricular aneurysms,
and even heart failure.
Just as frightening is this: T. cruzi can cross the
placenta. It’s estimated that as many as 315 babies
a year are born with Chagas in the United States.
I think of them as the “no-name babies” because
health officials don’t know who these children are.
Pregnant women are not routinely screened for Cha-
gas in the United States.
In 2014, a few years after my auntie’s death, I trav-
eled to Colombia. At the University of the Andes in
Bogotá, biologist Felipe Guhl has been studying the
kissing bug disease for more than four decades. There
I learned that these insects are homebodies, often
living where they don’t have to crawl far to reach
prey. That might be a human, a dog, a marsupial, a
raccoon —the bugs aren’t picky about which animals
they bite. In rural areas of Latin America, they live in
the cracks of mud houses during the day and come
out at night to feed. The bite, though painless, leaves
a small wound. The T. cruzi parasite is in the bugs’
feces and is transmitted when fecal material enters
the bite wound.
Guhl says that to eradicate Chagas, you’d have to
do away with wildlife—obviously not possible. Also,
given the beetle-like bug’s many species, “It’s like a
baseball game,” he says. If you get rid of one, “there
are other players on the bench.” And the parasite
itself is ancient. Guhl and an international team of
researchers found T. cruzi in 9,000-year-old mum-
mies from the deserts of Peru and Chile.
Having grown up hearing about Chagas disease
and knowing that a dreaded bug could kill me, the
last thing I wanted was to see one. And yet I did.JUNE 2019 19