Chagas disease is caused by a parasite that’s passed from bugs to animals and humans. If you’re bitten by a bug with the parasite, you mat notice a small, red, swollen area may appear within a week or two. You may also experience swelling of your upper and lower eyelids.

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Chagas disease is caused by the Trypanosoma cruzi parasite, which is transmitted to humans and animals by kissing bugs. It’s also known as T. cruzi infection or American trypanosomiasis, and it affects about 8 million people across North and South America. It causes an acute illness and has the potential to cause chronic health issues.

Here’s what you need to know about Chagas disease, its symptoms, and the various ways the disease can be transmitted.

Chagas disease is a vector-borne illness, which means it’s passed from bugs to humans and animals. Chagas disease is caused by the Trypanosoma cruzi parasite, which is transmitted by kissing bugs.

Transmission happens when a kissing bug with the parasite bites a person or animal and then poops on them. The poop may spread into the bite wound, into another cut, or through the eyes, nose, or mouth (mucous membranes), causing an infection.

Other methods of transmission include:

  • transmission at birth (from birthing parent to child)
  • blood transfusion with infected blood
  • organ transplantation with infected organs
  • ingestion of raw foods contaminated with infected poop from kissing bugs
  • exposure to laboratory samples

Chagas disease most commonly affects children, followed by women and men.

Chagas disease symptoms can be divided into two phases: the acute phase (within the first few months) and the chronic phase (decades later).

Some people may not experience any symptoms despite having an infection. Other symptoms may be difficult to pinpoint.

Acute phase symptoms

Acute phase symptoms may include swelling at the site of the insect bite, which is known as chagoma. People may also develop Romaña’s sign, which is swelling of the eyelid. This may happen if a person accidentally rubs infected poop from a kissing bug into their eye or if a person is bitten on their face (swelling will be on the same side as the bite).

Other acute phase symptoms include:

In rare cases, people may also experience myocarditis (inflammation of the heart) or meningoencephalitis (inflammation of the meninges and the brain) in the weeks or months following infection.

Chagas disease can reactivate, or recur, if a person becomes immunocompromised, and it may present with different symptoms.

Chronic phase symptoms

Chronic phase symptoms may take some time to recognize.

According to the Centers for Disease Control and Prevention (CDC), people often first develop an asymptomatic form of Chagas disease, called chronic indeterminate disease. People in the chronic phase may or may not develop additional symptoms or health issues.

The chronic phase can last indefinitely without treatment. However, about 60% to 70% of people with Chagas disease have an indeterminate form, meaning they test positive but do not experience symptoms. That said, people may transmit the infection through blood, organ donation, or the birth of a child — no matter the severity of their symptoms.

The most severe symptoms of Chagas disease affect the heart and gastrointestinal tract. The Trypanosoma cruzi parasite may exist in the body for decades after the initial infection.

People may experience:

Without prompt treatment, these symptoms can become life threatening, particularly for people who are immunocompromised.

Speak with your doctor if you think you may have Chagas disease. It can be diagnosed using a simple blood test. If you test positive, you’ll likely have an electrocardiogram (EKG) to trace your heart rhythm — even if you don’t have symptoms.

Treatment may include:

  • Antiparasitic medications: The medications benznidazole and nifurtimox are approved in the United States and are used to kill the parasite in the acute phase and beyond. These medications are not without side effects and require complex dosing and monitoring. Pregnant people, people with liver or kidney failure, and some people with neurological or mental health conditions should avoid these medications.
  • Other treatments: You may need other medications or procedures to address specific symptoms you’re experiencing, as well as for specific heart, gastrointestinal, or neurological issues.

If untreated, Chagas disease can contribute to long-term health issues. That’s why it’s important to consult your doctor if you think you may have Chagas disease and are experiencing any of the symptoms mentioned above.

Chagas disease is most common in Mexico, Central America, and South America. That is because the bugs transmitting this parasite are found in these parts of the world, particularly in areas with higher poverty rates.

According to the CDC, kissing bugs live in the walls and roofs of houses made from straw, mud, adobe, and other natural materials in remote areas of Latin America. The bugs may hide during the day and then come out at night, biting humans and animals when they sleep.

The CDC estimates that about 300,000 people live with Chagas disease in the United States. Most people with Chagas disease in the United States acquired the infection in areas with high transmission rates in Latin America.

However, there are reports of transmission in the southern United States, particularly in Texas, though these are rare. The disease is not widespread in humans, but it is an endemic disease in dogs.

While animals can and do get Chagas disease, household pets can’t transmit it to humans directly or through casual contact. For transmission to occur, a kissing bug with the parasite would need to bite a pet. The pet would then need to develop an infection and bite a human.

Humans can only transmit the disease to other humans during pregnancy and birth or via blood transfusions and organ donations.

Currently, there are no medications or vaccines to prevent Chagas disease. However, antiparasitic medications like benznidazole and nifurtimox can kill the parasite in the acute phase and beyond.

If you live in or plan to travel to an area with high transmission rates, speak with your healthcare professional about what you can do to prevent infection.

Avoid sleeping outdoors or in structures built from natural materials like mud and straw. Sleeping with a mosquito net in areas of high transmission may also be a useful prevention strategy.