Causes Chagas disease (South American trypanosomiasis)
Microbiology
Protozoan parasite
Epidemiology
Endemic throughout the Americas from the southern half of the United States to Argentina
Particularly in rural, impoverished areas
A small number of autochthonous cases of Chagas disease in the US
Reservoirs include armadillos, opossums, raccoons, woodrats, some other rodents, and domestic dogs
Triatomine vector species for trypanosomiasis belong to the genera Triatoma, Rhodnius, and Panstrongylus
Bugs live in substandard dwellings (especially wood, mud, or stone houses)
Vector is present from southern US to southern Argentina
Transmission is via feces, either in direct contact with mucous membranes (especially conjunctivae), breaks in the skin, or contaminating the bite of the insect
Can also be transmitted via blood transfusion or vertically from mother to child or via ingestion of contaminated food and drink
Pathophysiology
Infective metacyclic trypomastigotes from feces enter the skin or mucosa
Multiply in host cells as amastigotes, developing into trypomastigotes intracellularly and rupturing the cell, releasing more trypomastigotes
Chagoma develops at site of inoculation
Intracellular amastigotes visible as characteristic pseudocysts on histopathology
Hematogenous spread to distant sites, especially muscles, with the cycle repeating
Especially tropic for myocardium, where it causes biventricular enlargement, thinning of ventricular walls, apical aneurysms, and mural thrombi
Parasitemia maintained for years
Clinical Manifestations
Acute Disease
Often asymptomatic
Incubation period of about 1 week
Usually mild febrile illness, sometimes with hepatosplenomegaly, rash, edema, local inflammation
Incurs in 20% of infections
More common in children
Nodular lesions ("chagomas") may develop at site of inoculation
Romaña sign if periorbital, often with ipsilateral lymphadenopathy
Often 1-2 weeks after exposure
Acute myocarditis, pericardial effusion, and meningoencephalitis in 1-5%
Indeterminate Phase
Following acute infection, may enter a latent phase
Chronic Disease
Following acute infection can remain asymptomatic (indeterminate form)
Cardiac complications in 25-30% (1.5-5% per year)
Non-ischemic dilated biventricular (right more than left) cardiomyopathy with heart failure
Apical aneurysms and mural thrombi
Conduction defects, with heart blocks, bundle branch blocks, sinus node dysfunction, bradycardia, and ventricular arrhythmias
Can cause sudden cardiac death
GI involvement in 10-15%
Megaesophagus, with dysphagia, odynophagia, chest pain, cough, and regurgitation
May result in aspiration and recurrent pneumonias
Megacolon, with constipation and abdominal pain
Meningoencephalitis
Other: polyneuropathy, stroke syndrome
Immunocompromised Patients
May have reactivation following immune suppression or HIV
Severe acute infection; may have skin lesions and cerebral masses/abscesses
Meningoencephalitis
Diagnosis
Acute Disease
Direct microscopy blood film or tissue biopsy (e.g. lymph node, bone marrow, pericardial fluid, CSF)
In immunocompromised, these other samples are even more important
Hemoculture is only 50% sensitive and takes several weeks
Serology for IgM is useless
PCR is sensitive and specific
Xenodiagnosis
Indeterminate and Chronic Disease
No gold standard
Serology for IgG is most useful
Detectable after 6 to 9 months following infection
Many assays (ELISA, indirect hemagglutination, chemiluminescence, and IFA)
PCR (of blood) less sensitive
Management
Acute
Treatment is most useful in acute disease, congenital Chagas, and children with chronic infection up to 18 years
It can decrease illness severity and mortality
Start ASAP before infection can become established
However, treatment may not result in parasitologic cure
Treatment options
Nifurtimox: 90-120 day treatment course; AEs include anorexia, weight loss, neurologic symptoms
Benznidazole: 60 day treatment course; AEs include hypersensitivity, GI upset, rare polyneuropathy and agranulocytosis
Adverse events are common during treatment
Chronic
Less clear benefit to antiparasitic treatment
Cardiac disease
May benefit from pacemaker in patients with conduction disease
Monitor with ECG q6mo
May need heart transplantation, though this can become complicated by ongoing chronic infection or recrudescence
Megaesophagus: balloon dilatation or surgical management
Megacolon may need surgical management
Prevention
Screening immigrants and then following up with regular cardiac screening, if positive
Avoid sleeping in dilapidated dwellings in endemic countries, use insect repellent and bed nets
Improve housing in endemic areas
Canadian Blood Services
Samples are only tested for antibodies when increased risk is present, determined by the donor screening questions
