Chagas Disease: Creeping into Family Practice in the United States

TREATMENT CONSIDERATIONS

If there is a suspicion of Chagas disease, the patient should be referred to an infectious disease specialist for diagnosis and treatment. Nifurtimox and benz­nidazole are the only drugs that have been shown to improve the course of Chagas disease.⁵ However, neither drug is approved by the FDA, and both can only be obtained from the CDC, which makes treatment a challenge.⁹ In addition, up to 30% of patients terminate treatment due to the many adverse effects of these drugs.¹⁷

The dosage regimen for nifurtimox is 8-10 mg/kg/d divided into three doses for 90 days.¹⁰ Anorexia, weight loss, nausea, vomiting, and abdominal pain occur in up to 70% of patients.⁵ Irritability, insomnia, disorientation, and tremors can also occur. Neurotoxicity leading to peripheral neuropathy is dose dependent and requires treatment termination.⁵

Benznidazole is better tolerated and is active against the trypomastigotes as well as the amastigotes or intracellular form of the parasite.¹⁰ The dosage regimen for benznidazole is 5-7 mg/kg/d divided into two doses for 60 days.¹⁰ Dermatologic reactions such as rash, photosensitivity, and exfoliative dermatitis are the most common adverse effects. Peripheral neuropathy and bone marrow suppression are dose dependent and require therapy cessation.⁵

The CDC recommends treatment for all cases of acute disease (including congenital disease) regardless of age, and for chronic disease in patients up to age 50 who have not progressed to cardiomyopathy. In patients older than 50, treatment should be determined after weighing the potential risks and benefits (see Table 2).¹⁸

The success of treatment is determined in part by the phase of the disease. Cure rates in patients treated with either nifurtimox or benznidazole during the acute phase range from 65% to 80%.¹⁷ Chronic disease shows less of a response to traditional antiparasitic drug regimens, but higher rates of success are seen in younger patients.⁵ According to current estimates, successful treatment of chronic disease is limited to 15% to 30% patients.¹⁷ Treatment of congenital Chagas disease should begin as soon as the diagnosis is confirmed, and cure rates are greater than 90% if patients are treated within the first year of life.¹⁰ Treating congenital Chagas disease is important because the infection can be passed to future generations even if the disease never manifests with symptoms.¹⁹ However, if an expecting mother has known Chagas disease, antiparasitic medications are not recommended during the pregnancy because of a lack of fetal safety data for the two antiparasitic agents.²⁰ Instead, it is recommended that women of childbearing age be treated before pregnancy, as rates of congenital infection are 25 times lower in women who are treated than in those who are not.²¹

PRE- AND POSTEXPOSURE PATIENT EDUCATION

Patient education mainly focuses on how to prevent Chagas disease and prognosis once diagnosed. During travel to endemic areas, the use of insecticides and residing in well-built households are the most important prevention measures. No vaccine is available, and primary chemoprophylaxis of persons visiting endemic areas is not recommended due to the low risk for infection and concerns about adverse effects.¹³

The survival rate of those who remain in the indeterminate phase is the same as that of the general population. However, findings that most strongly predict mortality include ventricular tachycardia, cardiomegaly, congestive heart failure (NYHA class III/IV), left ventricular systolic dysfunction, and male sex.¹⁰ Patients diagnosed with Chagas disease should be strongly encouraged not to donate blood or organs.¹⁰ Some organ and blood donation organizations selectively or universally screen donated specimens; however, this screening is not required by law.⁵ Family members of those diagnosed with the disease should also be tested, especially if the patient is a woman who has children or who plans to become pregnant.¹⁰