300K Americans may live with a chronic, deadly disease transmitted by the 'kissing bug.' What is Chagas and why are doctors missing it?

Every summer, health officials warn Americans to be on the lookout for disease-carrying pests such as mosquitoes and ticks. But few people are aware of the kissing bug.

Triatomine bugs, commonly known as kissing bugs, are vectors for a dangerous parasite that can cause a debilitating illness in humans called Chagas disease. If left untreated, the infectious disease can become lifelong and painful, and in some cases lead to death.

The key is early treatment, but many Americans living with the disease are unaware they have it, and a recent study suggests doctors are underdiagnosing it.

“It’s such a neglected disease,” said Melissa Nolan, assistant professor at the University of South Carolina and lead author of the study published this week in Emerging Infectious Diseases, a peer-reviewed journal by the Centers for Disease Control and Prevention.

But health experts say the disease is not only difficult to diagnose – sometimes requiring multiple tests – it may require CDC intervention to treat.

“Chagas is not something that most doctors think about in the U.S.,” said Dr. Wesley Long, medical director of microbiology at Houston Methodist Hospital. Doctors are taught, “when you hear hoofbeats, think of horses, not zebras. Chagas is a zebra.”

What is Chagas disease and how can you get it from a kissing bug?

Chagas disease is caused by a parasite called Trypanosoma cruzi. The kissing bug can pick up this parasite when feeding on the blood of an infected animal.

Kissing bugs are commonly found in South and Central America, and Mexico, but doctors are starting to count cases in states like Texas, Arizona, Arkansas, Louisiana, Mississippi, Tennessee, Utah and California, according to a Texas A&M University program studying Chagas disease.

The rate of kissing bugs infected by the parasite is abnormally high compared with other insects that carry disease, said Gabriel Hamer, associate professor in the department of entomology at Texas A&M. Up to 60% of kissing bugs carry the parasite that causes Chagas, compared with only 0.1% of mosquitos that carry dengue, an infectious disease occurring in tropical areas.

Although more than half of kissing bugs carry the disease-causing parasite, Hamer said it’s still difficult for a person to be infected. Unlike mosquitoes or ticks, the parasite isn’t transmitted through saliva or blood during feeding. Instead, it’s transmitted through the bug's feces.

The kissing bug usually feeds around a person’s face when the person is sleeping, which is how the insect got its name. After feeding, the bug defecates near the wound. People normally become infected when they rub that fecal matter into the wound or near the eye.

“It’s a very inefficient form of transmission for humans,” Hamer said. “There’s been studies that suggest that if you have a positive kissing bug feeding on a human, it could take up to 2,000 feeding events for that human to become positive.”

If kissing bugs establish a colony in the house, they feed on a person multiple times, increasing the chance of transmitting the parasite, he said. Kissing bugs are most active when they venture out in search of a meal or a mate, which can start start as early as April and end as late as October, depending the region.

There are two phases of Chagas disease: acute and chronic. During the acute phase, a person may have no symptoms or mild ones, such as fever, fatigue, body aches, headache, rash, loss of appetite, diarrhea and vomiting, according to the CDC.

A swollen eyelid, known as Romaña’s sign, may also be a sign of acute Chagas. This typically occurs when the parasite infects the eyelid after rubbing bug feces into the eye.

Chronic Chagas can last for life. In those cases, the parasite invades the heart tissues, causing an enlarged heart, heart failure, an altered heart rate or cardiac arrest. It also can cause gastrointestinal complications including an enlarged esophagus or colon and lead to difficulties with GI functions.

The CDC estimates more than 300,000 people in the U.S. live with Chagas disease. One in 3 people develop the chronic stage of the disease, which can lead to heart attack, stroke or sudden death.

Doctors may be underdiagnosing Chagas disease

Patients can recover with early detection and treatment, but if left untreated, the infection can become a lifelong, painful and deadly disease. The problem is, most people infected in the U.S. don’t know they have Chagas disease, and this week's study suggests doctors may be partly to blame for missing diagnoses.

From August 2015 to July 2017, researchers looked at 97 patients with a heart condition called nonischemic cardiomyopathy in a Houston hospital. All came from a country or lived in an area where kissing bugs are found, putting them at risk for Chagas disease, yet doctors never tested them.

Overall, 7% of those patients seeking treatment for heart failure management tested positive for the Chagas disease parasite by the CDC, according to the report.