Neglected Parasitic Infections: What Every Family Physician Needs to Know



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Am Fam Physician. 2014 May 15;89(10):803-811.

This clinical content conforms to AAFP criteria for continuing medical education (CME). See CME Quiz Questions.

Author disclosure: No relevant financial affiliations.

Neglected parasitic infections, including Chagas disease, toxocariasis, cysticercosis, and toxoplasmosis, affect millions of persons in the United States. Relatively few resources have been devoted to surveillance, prevention, and treatment of these diseases. Chagas disease primarily affects Latin American immigrants and can cause heart failure and death if not treated. Immediate antiparasitic treatment is indicated for most patients with acute Chagas disease. Treatment is recommended for patients younger than 18 years who have chronic Chagas disease and is generally recommended for adults younger than 50 years who do not have advanced cardiomyopathy; treatment decisions for other patients should be made on an individual basis. Toxocariasis primarily affects children and can cause gastrointestinal, respiratory, and ophthalmologic disease. Treatment options include albendazole and mebendazole. Patients with ocular infection require referral to an ophthalmologist. Neurocysticercosis, a form of cysticercosis, is the most common infectious cause of seizures in some parts of the United States. Initial treatment should focus on symptom control. Humans generally acquire toxoplasmosis by eating undercooked contaminated meat or ingesting things that have been contaminated with cat feces. Congenital infection can result in miscarriage or adverse fetal effects. Treatment is recommended for immunosuppressed persons, pregnant women, and immunocompetent persons with severe symptoms.

Neglected parasitic infections, including Chagas disease, toxocariasis, cysticercosis, and toxoplasmosis, can cause severe illness, but limited resources have been devoted to better understanding their impact and burden. Physicians may not be familiar with these infections because their clinical presentation, diagnosis, and treatment are typically not emphasized during medical training. However, it is crucial for family physicians to understand the basic principles of diagnosis and treatment of these diseases. A summary of the key points about epidemiology, clinical manifestations, diagnostic evaluation, and treatment for each disease is presented in Table 1.

Table 1.

Key Points About Chagas Disease, Toxocariasis, Cysticercosis, and Toxoplasmosis

DiseaseEpidemiology and transmissionClinical manifestationsDiagnosisTreatment

Chagas disease (American trypanosomiasis)

More than 300,000 persons in the United States are infected; more common in immigrants from Mexico and Central or South America, and in those who have visited endemic areas

Transmission is most often vector-borne (triatomines), congenital, or via blood transfusion or organ transplantation

Blood donations are screened for the disease; donors whose blood tests positive cannot donate again

Acute infection:

Typically four to eight weeks after infection; usually asymptomatic; nonspecific febrile illness, swelling around the bite site

Chronic infection:

20% to 30% of persons develop symptoms, including cardiac and gastrointestinal manifestations; increased risk of stroke

Congenital infection:

Usually asymptomatic; anemia, hepatosplenomegaly, low Apgar scores, low birth weight, thrombocytopenia; rarely, meningoencephalitis, myocarditis

Acute and congenital infections:

Direct microscopy of peripheral or umbilical cord blood to detect parasites; polymerase chain reaction testing also available

Chronic infection:

No or few parasites in the blood; multiple serologic tests with varying sensitivity and specificity are available; at least two positive results on serologic tests required for diagnosis

Infection is lifelong without treatment; persons with acute or congenital infection should be treated, as should immunocompromised persons with reactivated infection; pregnant women and persons with severe renal or hepatic insufficiency should not be treated; for chronic disease, treatment is recommended in persons younger than 18 years and in those younger than 50 years who do not have severe cardiomyopathy; all others should be treated on a case-by-case basis

Treatment options include nifurtimox or benznidazole (available through the Centers for Disease Control and Prevention)

Toxocariasis

More common in children, pet owners, and persons with geophagia; estimated serologic prevalence in the United States is 13.9%

Transmission occurs by ingesting Toxocara eggs in soil contaminated with feces from an infected dog or cat, or by eating undercooked meat from an infected animal

Usually asymptomatic

Visceral infection:

Abdominal pain, anemia, anorexia, coughing, eosinophilia, fatigue, fever, hepatomegaly, hypergammaglobulinemia, meningoencephalitis, wheezing

Ocular infection:

Peripheral granuloma with traction bands, posterior pole granuloma, strabismus, subretinal granulomatous mass, unilateral vision loss

Toxocara antibody test (does not differentiate between acute and previous infection); stool examination is not useful because eggs are not excreted by humans

Treatment options include albendazole (Albenza) and meb

The Authors

DANA WOODHALL, MD, is a medical officer in the Parasitic Diseases Branch of the Centers for Disease Control and Prevention in Atlanta, Ga.

JEFFREY L. JONES, MD, MPH, is a medical officer in the Parasitic Diseases Branch of the Centers for Disease Control and Prevention.

PAUL T. CANTEY, MD, MPH, is a medical officer in the Parasitic Diseases Branch of the Centers for Disease Control and Prevention.

PATRICIA P. WILKINS, PhD, is an associate director for laboratory science in the Parasitic Diseases Branch of the Centers for Disease Control and Prevention.

SUSAN P. MONTGOMERY, DVM, MPH, is a veterinary medical officer in the Parasitic Diseases Branch of the Centers for Disease Control and Prevention.

Address correspondence to Dana Woodhall, MD, Centers for Disease Control and Prevention, 1600 Clifton Rd., Mail Stop D-03, Atlanta, GA 30333 (e-mail: dqw6@cdc.gov). Reprints are not available from the authors.

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