ALSO KNOWN AS American trypanosomiasis, Chagas disease is a debilitating and potentially fatal infection. It's typically spread to humans through blood-feeding insects called triatomines, or “kissing bugs,” that are infected with the parasite Trypanosoma cruzi.1
According to the CDC, Chagas disease affects between 8 and 11 million people in Latin America and up to 300,000 immigrants living in the southern United States and Hawaii.2 Although triatomines are found in the United States, they're rarely infected with the T. cruzi protozoa, causing fewer than a dozen cases since 1955.2,3
If untreated, patients with Chagas disease may experience debilitating and sometimes life-threatening complications, including cardiac disease (conduction abnormalities, apical aneurysm) or gastrointestinal problems (megacolon, megaesophagus). Infection with T. cruzi also increases the risk of stroke.1
Transmitting T. cruzi
Triatomines, also known as reduviid bugs, live in nests housed in cracks and crevices in walls and roofing materials of homes during the daylight hours. At night, the insects venture out for a blood meal from sleeping human hosts, leaving a trail of infected feces behind. Human hosts may rub the feces into the fresh bite or other breaks in their skin or their eyes, mouth, or other mucous membranes, infecting themselves with T. cruzi. Other mechanisms for infection include ingestion of foods contaminated with infectious triatomine feces, blood transfusions, organ transplants, and from mother to fetus.2,3
Signs and symptoms
Chagas disease has two phases: acute and chronic. In the acute phase, which lasts for a few months, patients may experience no signs or symptoms or mild signs and symptoms such as fatigue, fever, malaise, hepatomegaly, lymphadenopathy, rash, gastritis, anorexia, and the Romaña sign (orbital edema, conjunctivitis, and lymphadenopathy on one side of the face).4 Patients under age 2, older adults, and those with a compromised immune system may experience fatal complications, which include heart failure, myocarditis, and meningoencephalitis.4–6
When signs and symptoms once again present, the patient has progressed to the chronic phase. In this phase, the parasite has moved from the blood into tissues.
Most individuals with chronic Chagas disease remain asymptomatic; only 20% to 30% of those infected with T. cruzi develop chronic phase signs and symptoms, which may include:
- dysphagia due to esophageal achalasia
- cardiac dysrhythmias
- heart failure
- constipation resulting in intestinal hypertrophy, necrosis, and gangrene.4–6
Some patients may have an indeterminate form of the disease, where they have positive tests for T. cruzi but no signs or symptoms of gastrointestinal disease or cardiomyopathy. Twenty to 30% of these patients will eventually progress to clinically evident Chagas disease.7
When assessing a patient, ask about recent travel to Latin America, a history of organ transplants and blood transfusions, a familial history of Chagas disease (especially in children of mothers diagnosed with Chagas disease), or residence in an endemic region (Mexico, Central America, and South America).8
Testing for T. cruzi can be direct (detecting parasites during the acute phase) or indirect (detecting antibodies that bind to T. cruzi antigens present in the blood). Direct testing methods include microscopic exam of blood and tissue samples. Indirect testing methods include enzyme-linked immunosorbent assay for T. cruzi antibodies and a urine test for T. cruzi antigens.8,9
Patients under age 50 with acute or chronic Chagas disease are treated with nifurtimox or benznidazole. Both drugs can cause serious adverse reactions that increase in frequency and become more severe in those over age 50, so the decision to treat patients over age 50 with chronic Chagas disease is individualized based on the patient's age, clinical status, preference, and overall health.10 Contraindications for treatment include severe hepatic and/or renal disease. Because no studies have been conducted on infant exposure through breast milk, nursing mothers shouldn't be treated with nifurtimox or benznidazole.10 Nifurtimox and benznidazole aren't FDA approved and may be obtained only from the CDC.
Common adverse reactions to benznidazole include allergic dermatitis, peripheral neuropathy, anorexia, weight loss, and insomnia. The most common adverse reactions of nifurtimox are anorexia, weight loss, polyneuropathy, nausea, vomiting, headache, and dizziness.
Because pharmacologic treatments aren't completely effective in treating Chagas disease after the acute phase has passed, the most effective way to combat the disease is education. Advise patients traveling to endemic areas to avoid sleeping in rustic dwellings, use insect repellent and mosquito nets, wear long sleeves, and tuck pants into their socks to reduce skin exposure to insect bites. Warn patients diagnosed with Chagas disease not to donate blood or organs, and caution infected women of childbearing potential to consult their healthcare provider regarding pregnancy and the risks of fetal transmission.4