Should You Be Worried About Chagas Disease?

In medical school, doctors are taught a guiding principle: "When you hear hoofbeats, think horses, not zebras." It's a reminder to consider the most common diagnosis before a rarer one.

But sometimes, those hoofbeats are zebras — and Chagas disease could be one of them.

You're not alone if you've never even heard of the disease. Vector-borne illnesses you're likely more familiar with include Lyme disease, West Nile virus, Rocky Mountain spotted fever and Zika virus.

Since Chagas disease isn't considered "endemic" to the U.S., its prevalence and spread aren't closely monitored. But that's changing — especially in southern states, like Texas.

"Chagas disease is caused by a parasite called Trypanosoma cruzi, and while it's often associated with rural areas in Latin America, evidence is mounting that it's likely more common in the U.S. than we think," says Dr. Wesley Long, medical director of diagnostic microbiology at Houston Methodist.

In fact, new findings released by the CDC suggest that Chagas disease should be classified as endemic to the U.S.

Here's everything you need to know about the disease:

What Is Chagas disease?

Some vector-borne diseases are spread by ticks, others by mosquitoes. The Chagas parasite is spread by the triatomine bug, more commonly known as the "kissing bug."

These bugs feed on the blood of infected animals or people, picking up the parasite. During the feeding process, they often defecate. If parasite-laden feces enter the body — by being scratched into the bite wound or rubbed into the eyes or mouth — it can lead to infection.

How common is Chagas disease in the U.S.?

A systematic review found 29 confirmed and 47 suspected cases of locally acquired Chagas disease in the U.S. between 2000 and 2018. But experts believe these numbers vastly underrepresent the true number of infections.

"While some states, like Texas, Arizona and Arkansas, have started tracking Chagas cases in the last decade, most states haven't — making it difficult to understand the full scope of the disease," adds Dr. Long.

While the exact prevalence of Chagas disease in the U.S. is largely unclear, here's what is known:

• Kissing bugs have been identified in 29 U.S. states
• Evidence suggests that about half of all kissing bugs carry the Chagas parasite
• While most cases of Chagas disease occur in Latin America, locally acquired infections have been documented in eight U.S. states, including Texas

"There's a general lack of familiarity about the disease, from both the public at large but also health care providers," adds Dr. Long. "The reality is that most infections likely go undiagnosed and subsequently unreported."

Chagas disease symptoms: Acute vs. chronic

Chagas disease has two stages: acute and chronic.

In the acute phase, one of the most distinctive signs is Romaña's sign, which is swelling of the eyelid caused by the parasite entering through the eye.

Less specific symptoms include:

• Fever
• Fatigue
• Body aches
• Headache
• Diarrhea or vomiting

After the acute phase, the disease can enter a chronic stage that lasts for years. While most of those infected never experience symptoms, around 20% eventually develop life-threatening heart issues or severe digestive problems.

"Yes, it's rare, but Chagas disease is something doctors should be thinking about in the right patients," warns Dr. Long. "This is what's needed to catch the disease before cardiac symptoms appear and become severe."

Why early diagnosis matters

Early treatment of Chagas disease can be lifesaving. Unfortunately, many people aren't diagnosed until they've entered the chronic stage, when symptoms become severe and harder to treat.

At that point, doctors rely on antibody testing to confirm infection, but these tests aren't always reliable.

"A drawback of serological tests is that you're looking for antibodies that react against the parasite, but you may have antibodies that aren't due to the infection but still react with the test, giving you a false positive," explains Dr. Long.

This can make doctors suspicious of a positive test result, but Dr. Long adds that it's important to consider follow-up testing when unexplained cardiac or gastrointestinal symptoms are accompanied by risk factors. For instance, the risk of Chagas disease is higher in southern states, where there are more kissing bugs. Other risk factors include living in a rural area, frequent hunting or camping, and outdoor or agricultural work.

How to reduce your risk of Chagas disease

It's always a good idea to protect yourself, your family and your animals from insects that carry disease.

Here are some practical tips to help reduce your risk of Chagas disease:

Seal up your home: Make sure windows, doors and vents are properly screened and sealed to prevent kissing bugs from entering your house.

Check for bugs: Regularly inspect your home, pet areas and outdoor spaces for kissing bugs, especially in warmer months.

Avoid sleeping outdoors near brush: If camping or hunting, use tents with netting and avoid sleeping directly on the ground near woodpiles or animal nests.

Protect pets and kennels: Keep dog kennels clean and away from wooded or brushy areas. (Related: Can My Dog Get Me Sick?)