Chagas disease is an insect-transmitted parasitic disease common in South and Central America.
Causes, incidence, and risk factors
Chagas disease is caused by Trypanosoma cruzi, a parasite related to the African trypanosome that causes sleeping sickness. It is spread by reduvid bugs and is one of the major health problems in South America, where 20 million people are infected. Due to immigration, approximately 500,000 people in the United States are believed to be infected.
Risk factors for Chagas disease include living in Central or South America, poverty, living in a hut where the reduvid bugs live in the walls, and receiving a blood transfusion from a person who carries the parasite, but does not have active Chagas disease.
Chagas disease has two phases - acute and chronic. The acute phase may have no symptoms or have very mild symptoms. Symptoms of the acute phase include swelling and reddening at the site of infection (where the blood-sucking insect caused the initial infection).
This may be followed by swelling of one eye. Lymph nodes that drain the area of the insect bite may become swollen. As the parasite spreads from the bite site, the patient develops fever, malaise, and generalized swelling of the lymph nodes. The liver and spleen may become enlarged.
The disease goes into remission after the acute phase and may become chronic with no further symptoms for many years. When symptoms finally develop, they appear as heart disease (cardiomyopathy) and digestive abnormalities.
Patients may develop congestive heart failure. Swallowing difficulties may be the first symptom of digestive disturbances and may lead to malnutrition. Patients who have parasitic infection of the colon may experience abdominal pain and constipation. Death is usually caused by heart disease.
- history of exposure in an area where Chagas disease is known to occur
- swollen red area at site of previous insect bite
- enlarged lymph nodes
- swelling of one eye
- irregular heartbeat (arrhythmia)
- rapid heartbeat (tachycardia)
- swallowing difficulties
Signs and tests
- Physical examination can confirm the symptoms. It may demonstrate signs of heart failure (or cardiomyopathy) in the chronic form.
- Peripheralblood smear demonstrates motile trypanosomes in the acute form.
- Blood culture demonstrates Trypanosoma cruzi in the acute form.
- ELISA can show past infection with Trypanosoma cruzi in the chronic form.
The acute phase should be treated. Benznidazole has been shown to be effective. Experimental treatment may include nifurtimox. Treating the chronic phase with antibiotics is not helpful. Instead, the symptoms of heart and intestinal disease should be treated.
Approximately 30% of infected and untreated people will develop chronic or symptomatic Chagas disease. It may take more than 20 years from the time of the original infection to develop heart or digestive problems.
Abnormal heart rhythms (arrythmias, ventricular tachycardia) may cause sudden death. Once congestive heart failure develops, death usually occurs within several years.
- congestive heart failure
- enlargement of the esophagus (megaesophagus) with swallowing difficulty
- enlargement of the colon (megacolon) with constipation and abdominal pain
Calling your health care provider
Call for an appointment with your health care provider if symptoms suggestive of Chagas disease develop.
Insect control with insecticides and housing structures less conducive to high insect populations will help control spread of the disease.
Blood banks in Central and South America screen donors for previous exposure to the parasite, and the blood is discarded if the donor tests positive. Because the incidence of Chagas disease is low in the US, blood banks here do not screen donors for Chagas disease.
by David A. Scott, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.