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FeedbackChagas disease, also called American trypanosomiasis, is an infection caused by the protozoan parasite Trypanosoma cruzi, often following contact with triatomine insects (ie, kissing bugs). Although diagnosis is important to prevent possible chronic manifestations of the disease (eg, cardiomyopathy), the diagnostic process may be complicated by a lack of symptoms in the acute and chronic phases. Chagas disease poses a particular threat to immunocompromised individuals, such as organ transplant recipients. Appropriate laboratory testing for Chagas disease depends on the suspected phase of infection but can include microscopic parasite identification via blood smear, molecular detection by polymerase chain reaction (PCR), and/or serologic testing involving two or more methods that detect antibodies to different antigens.
Quick Answers for Clinicians
Chagas disease is predominantly transmitted by triatomine insects (ie, kissing bugs), which are endemic to Latin America but may also be found in parts of the southern United States.
At-risk individuals include those who:
Because parasitemia peaks during the acute phase of Chagas disease, testing techniques that detect Trypanosoma cruzi within a blood sample (eg, blood smear or polymerase chain reaction [PCR]) can be applied. By contrast, typically few or no parasites are detectable after 8-12 weeks of infection. Therefore, during the chronic phase, serology is necessary to diagnose Chagas disease. For more information about the preferred testing for either phase, see the Preferred Acute- and Chronic-Phase Testing Strategy table.
Routine screening of pregnant individuals for Chagas disease is not recommended. However, targeted screening may be appropriate in individuals who are pregnant or considering pregnancy when patient history reveals one or more risk factors for the disease. In general, individuals who have lived in Mexico, Central America, or South America face an increased risk of infection.
Yes. The American Society of Transplantation (AST) recommends targeted screening of any prospective transplant recipients who are at risk for Chagas disease (eg, those who report a personal or maternal history of living in an endemic region). Additionally, the Chagas in Transplant Working Group recommends screening prospective organ donors who may be at risk for Chagas disease.
Indications for Testing
Laboratory testing for Chagas disease is indicated in individuals who are at risk when clinical findings point to acute- or chronic-phase infection.
Additionally, selective screening is recommended for at-risk individuals who are:
- Pregnant or plan to become pregnant
- Organ transplant candidates or recipients
- Prospective living organ donors
Laboratory Testing
Accurate diagnosis of Chagas disease requires the use of appropriate testing for the suspected stage of infection (either acute or chronic), which corresponds to detectable parasitemia. In general, the same testing methods apply across patient populations (eg, infants, immunocompromised individuals, etc.). Blood smear and PCR testing may be used when acute-phase Chagas disease is suspected, whereas serology is preferred to detect chronic-phase infection. Because no single serologic test is adequately sensitive or specific to diagnose Chagas disease, two or more serologic methods are needed to confirm infection.
| Phase of Chagas Disease | Duration | Presentation | Preferred Testing Strategy |
|---|---|---|---|
|
Acute |
Lasts 8-12 wks after infection |
Asymptomatic or mild febrile illnessa with possible swelling at the initial site of infection T. cruzi is demonstrable within a blood sample |
Use blood smear (eg, Giemsa stain)b or molecular detection by PCRc |
|
Chronic (follows acute illness) |
Lasts indefinitely without treatment |
Typically asymptomatic 20-30% of infections result in cardiovascular and/or gastrointestinal manifestations, such as:
|
Use ≥2 serologic methods that detect antibodies to different antigensd Common methods include EIA, IFA, and immunoblot |
|
aInfants born with Chagas disease can be asymptomatic or may present with symptoms such as prematurity, low weight, anemia, thrombocytopenia, etc. bBlood smear is the most common method of identifying acute Chagas disease and is commercially available. cPCR testing is the most sensitive option to detect early acute-phase Chagas disease and can be ordered through the CDC. dSerology may yield false-positive results in infants <12 mos of age, before the dissipation of maternal antibodies. |
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EIA, enzyme immunoassay; IFA, immunofluorescent antibody test Sources: CDC Yellow Book, 2019 ; La Hoz, 2019 ; CDC, Congenital Chagas disease, 2021 ; CDC, Chagas disease molecular detection, 2021 |
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Organ Transplantation
Selective screening is recommended for both organ transplant recipients and living donors who are at risk for Chagas disease to identify the possibility of transmission or reactivation and mitigate potential serious complications.
The American Society of Transplantation (AST) recommends dual-method serologic testing to screen for chronic Chagas infection in any transplant candidate who may be at risk for the disease. A combined testing approach involving PCR alongside blood smear should be used when reactivation of Chagas disease is suspected.
Systematic monitoring is recommended in transplant recipients when reactivation or donor transmission of the disease is possible. PCR testing, available through the CDC, is the preferred means of detecting acute infection in at-risk transplant recipients and should be used alongside blood smears in a coordinated testing schedule, as indicated in the following table.
| Time Since Transplant (Mos) | Testing Frequencyb,c |
|---|---|
|
1-2 |
Weekly |
|
3 |
Biweekly |
|
4-9 |
Monthly |
|
10+ |
≥Monthlyd |
|
aRecommendations are from the AST. CDC recommendations vary; for additional details, see Preventing Chagas disease in transplant recipients: donor screening and recipient monitoring. bMore frequent monitoring may be indicated in transplant recipients with chronic Chagas disease when adjusting immunosuppression to treat transplant rejection. cTesting in addition to scheduled monitoring should be performed if an at-risk transplant recipient develops unexplained febrile illness. dFrequency of testing can be reduced in stable patients with consistent negative test results. |
|
ARUP Laboratory Tests
Use to identify T. cruzi within a blood sample during the acute phase of infection
Stain
Aids in the diagnosis of chronic-phase Chagas disease
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Medical Experts
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References
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CDC - Yellow book: trypanosomiasis
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. CDC Yellow Book: trypanosomiasis, American (Chagas disease). [Reviewed: Jun 2019; Accessed: Sept 2021]
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30900295
La Hoz RM, Morris MI; Infectious Diseases Community of Practice of the American Society of Transplantation. Tissue and blood protozoa including toxoplasmosis, Chagas disease, leishmaniasis, Babesia, Acanthamoeba, Balamuthia, and Naegleria in solid organ transplant recipients- guidelines from the American Society of Transplantation Infectious Diseases Community of Practice. Clin Transplant. 2019;33(9):e13546.
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CDC - Congenital Chagas
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Parasites - American trypanosomiasis (also known as Chagas disease): congenital Chagas disease. [Reviewed: Jun 2021; Accessed: Sep 2021]
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CDC - Preventing Chagas
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Preventing Chagas disease in transplant recipients: donor screening and recipient monitoring. [Updated: Apr 2015; Accessed: Sep 2021]
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OPTN - Recognizing seasonal-geographically endemic
U.S. Department of Health and Human Services, Organ Procurement and Transplantation Network. Recognizing seasonal and geographically endemic infections in organ donors: considerations during living donor evaluation. [Updated: Nov 2014; Accessed: Sep 2021]
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21401868
Chin-Hong PV, Schwartz BS, Bern C, et al. Screening and treatment of Chagas disease in organ transplant recipients in the United States: recommendations from the Chagas in Transplant Working Group. Am J Transplant. 2011;11(4):672-680.
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CDC - Trypanosoma: health professionals: diagnosis
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Parasites - American trypanosomiasis (also known as Chagas disease): diagnosis. [Reviewed: Mar 2019; Accessed Sep 2021]
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CDC - Chagas disease molecular detection
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Chagas disease molecular detection. [Reviewed: Sep 2021; Accessed: Sep 2021]