Comments
INITIAL SYMPTOMS: "Chagoma" at site of triatomine insect bite, fever, lymphadenopathy, and hepatosplenomegaly, [CCDM] Acute disease resolves spontaneously in 4-8 weeks; [Harrison, p. 773]
FINDINGS:
The majority of infections are asymptomatic. Only a small percentage of patients with acute disease have Romana's sign (swelling of upper and lower eyelids of one eye). Chronic disease develops in about 20-30% of infections. [CCDM, p. 633-4] The chagoma is a red and indurated skin lesion at the bite site appearing 1-2 weeks after the event. Unilateral bipalpebral edema (Romana's sign) is a form of Parinaud's oculoglandular syndrome. [Guerrant, p. 1085, 1005] There are two distinct syndromes: acute and chronic (late sequelae). Acute disease usually affects children, in whom the diagnosis is seldom made. Cases are usually mild, but a small proportion of patients die from myocarditis and meningoencephalitis. Survivors enter a latent phase that lasts for years or decades, and 20-40% of these develop chronic Chagas disease. Patients with chronic disease develop heart conduction abnormalities leading to congestive heart failure and syncope. Autonomic nervous disease causes megaesophagus (dysphagia and chest pain) and megacolon (constipation and bowel obstruction). [Merck Manual, p. 1376-7] Most infections are asymptomatic. About 20-30% of patients develop chronic disease after a long asymptomatic period. [CDC Travel, p. 333] The chagoma is accompanied by local lymph node involvement. Patients with heart involvement may experience dizziness, syncope, and sometimes seizures. Patients with megaesophagus have dysphagia, chest pain, cough, and severe weight loss. Reactivation of infection occurs in AIDS patients, and brain abscesses are a common manifestation. [PPID, p. 3111-2] Chronic aspiration pneumonitis is a complication. [Guerrant, p, 693]
EPIDEMIOLOGY:
Reservoirs include humans and over 150 species of wild and domestic animals. Freshly excreted bug feces of the triatomine vectors contain trypanosomes that may infect humans through mucous membranes, conjunctivae, and skin abrasions. Successful programs based on application of residual insecticides have substantially reduced transmission in Uruguay, Chile, and parts of Brazil. [CCDM, p. 633-7] 10% to 20% of recipients may become infected after transfusion of a single unit of contaminated blood. [ID, p. 2330-3] Among tourists returning to the US from endemic countries, only one case has been reported. [PPID, p. 3113] An estimated 300,000 immigrants in the US are infected with T. cruzi. Only 6 cases of autochthonous transmission have been reported in the US (TX, LA, TN, and CA). Blood donors were first screened for T. cruzi in 2007. The rate of infection in donors is about 1 in 13,300. [PPID, p. 3111] Transmission may occur by ingesting contaminated food or water. [CDC Travel, p. 332] Chagas' disease mainly affects the rural poor. [Cecil, p. 2021]
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