Chagas Disease

How Chagas disease spreads

Triatomine bugs, nicknamed kissing bugs because they often bite the face at night, live in cracks of mud, adobe and thatched houses. When an infected bug feeds, it defecates near the bite. The parasites enter the body when the feces are rubbed into the bite, eyes or mouth.

Other routes:

• congenital: from mother to baby during pregnancy (about 1 to 5% of babies born to infected mothers)
• blood transfusion and organ transplant (US blood donations are now screened)
• contaminated food or drink, such as fruit juice contaminated with bugs, which can cause outbreaks
• laboratory accidents

Kissing bugs are found in the southern US, but bug-to-human transmission in the US is rare. Most US cases are in people who were infected in Latin America.

Symptoms

Acute phase (first 8 to 12 weeks)

Most people have no symptoms or mild, flu-like illness:

• fever, tiredness, body aches, headache
• swollen lymph nodes, rash, loss of appetite
• swelling at the bite site (chagoma)
• Romaña's sign: painless swelling of one eyelid when the parasite entered through the eye

Rarely, especially in young children or people with weak immunity, the acute phase causes inflammation of the heart muscle or brain.

Chronic indeterminate phase

The parasite remains in the body, but there are no symptoms and tests of the heart and gut are normal. Most people stay in this phase for life.

Chronic symptomatic phase

Ten to thirty years later, about 20 to 30% develop:

• Chagas cardiomyopathy: the most serious complication. Heart rhythm problems (heart block, ventricular arrhythmias), an enlarged, weakened heart and heart failure, blood clots and stroke, and sudden death.
• Digestive disease: an enlarged esophagus (megaesophagus) causing difficulty swallowing and regurgitation, similar to achalasia, or an enlarged colon (megacolon) causing severe constipation and risk of bowel twisting.

Who should be tested

The CDC and the American Heart Association recommend testing people who:

• were born or lived for a long time in Mexico, Central America or South America, especially in rural areas
• have a mother or sibling with Chagas disease
• are pregnant, or of childbearing age, and from endemic areas
• have unexplained heart conduction problems or cardiomyopathy and came from an endemic region

Diagnosis

• Acute phase: parasites can be seen in a blood smear or detected by PCR.
• Chronic phase: parasites are rarely in the blood, so diagnosis uses two different antibody blood tests, both positive.
• Newborns: PCR in the first months, then antibody tests after 9 to 12 months.

After diagnosis, doctors assess the heart with an ECG (right bundle branch block and left anterior fascicular block are typical), an echocardiogram, and sometimes Holter monitoring or cardiac MRI. Swallowing studies or barium enema are used if there are digestive symptoms.

Treatment

Antiparasitic medicine

Two medicines, benznidazole and nifurtimox, are taken for about 2 months. Treatment is:

• strongly recommended for acute infection, congenital infection, children and reactivated infection
• generally offered to adults up to about 50 without advanced heart disease
• individualized for older adults and those with established cardiomyopathy

Side effects are common, especially in adults: rash, stomach upset, weight loss and nerve symptoms. They are not used during pregnancy. The cure rate is highest in infants and children.

Treating complications

• Heart: heart failure medicines, antiarrhythmic drugs, pacemakers for heart block, implantable defibrillators, blood thinners to prevent stroke, and sometimes heart transplant.
• Digestive: diet changes, dilation or surgery for the esophagus; laxatives and surgery for megacolon.

Prevention

• In endemic areas: use bed nets, insecticide, and plaster walls and fill cracks; store food safely.
• Travelers to rural areas should avoid sleeping in poorly constructed houses.
• Screening of blood donors and organ donors.
• Screening pregnant women from endemic areas and treating infected women after pregnancy, which reduces transmission to future babies.
• There is no vaccine.

Frequently asked questions

What are the symptoms of Chagas disease?

Early infection is usually mild or symptom-free, with possible fever, aches, swollen glands, swelling at the bite or a swollen eyelid. Years later, some people develop palpitations, fainting, breathlessness, heart failure or stroke, or difficulty swallowing and severe constipation.

How do you get Chagas disease?

Most people are infected when feces from an infected kissing bug get into a bite wound, the eyes or the mouth. It can also pass from mother to baby, through blood transfusions or organ transplants, and through contaminated food or drink.

Is Chagas disease curable?

It is often curable when treated early, especially in babies and children. Treatment in adults with chronic infection may reduce the risk of heart disease but is less certain to clear the parasite. Heart and gut complications can be managed but not reversed.

Is Chagas disease found in the United States?

Yes. Kissing bugs live in the southern US, but local transmission is rare. An estimated 300,000 or more people living in the US have Chagas, nearly all infected in Latin America. Many do not know, so testing is recommended for those at risk.

Can Chagas disease spread from person to person?

Not through casual contact. It can spread from mother to baby during pregnancy, and through blood transfusions or organ transplants from infected donors. It does not spread by touching, kissing or sharing food with an infected person.