Infectious colitis

Chagas disease (trypanosomiasis)

Editorial Board Member: Raul S. Gonzalez, M.D.
Elliot Weisenberg, M.D.

Last author update: 1 October 2017
Last staff update: 8 June 2021

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PubMed Search: Colon chagas disease

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Chagas disease (trypanosomiasis). website. Accessed June 1st, 2023.
Definition / general
  • Colonic involvement in the chronic phase of infection by the flagellate protozoan Trypanosoma cruzi, causing chagasic megacolon
Essential features
  • Infection most commonly involves the heart and GI tract (esophagus is most frequent site, followed by colon)
  • Patients with chagasic megacolon suffer from chronic constipation and abdominal pain; in severe cases, there may be several weeks between bowel movements
  • Histology shows ganglionitis with neuronal cell depopulation
  • Also known as American trypanosomiasis
ICD coding
  • B57.3 Chagas disease (chronic) with digestive system involvement
  • B57.32 Megacolon in Chagas' disease
  • Worldwide, an estimated 100 million people are at risk (Am J Trop Med Hyg 2014;90:814); 8 million are chronically infected (CDC - Chagas Disease: Detailed FAQs) with 56,000 new infections a year (Am J Trop Med Hyg 2014;90:814) and 12,000 deaths (PAHO WHO - Chagas disease)
  • Chagas disease is endemic in all of the Western hemisphere south of the United States
  • Vector borne transmission does not occur in the Caribbean
  • Insect vectors are found in the southern United States but vector borne infection is rare there
  • It is estimated that 300,000 residents of the United States are infected, the vast majority are immigrants from countries where the disease is endemic (CDC - Chagas Disease: Epidemiology and Risk Factors)
  • There are very rare reports of disease in tourists
  • Imported cases may occur worldwide
  • Insect vector is more common in outdoor settings, including animal burrows, kennels, dog houses, chicken coops, under porches, between rocky structures and wood piles
  • It is more commonly found in rural settings
  • Deforestation for agriculture has played a role in its spread
  • Indoors, it prefers cracks, nooks, crannies and holes typically found in dilapidated housing, including homes with mud walls and thatched roofs, accounting for its association with poverty
  • Due to migration, disease is also found in urban settings
  • Far less common routes of transmission are congenital, consuming contaminated food or drink, blood transfusion and organ transplants
  • 5% of infants born to infected mothers become infected
  • Public health efforts, including improving housing and public hygiene, as well as bed nets and screening donated blood, have resulted in declining numbers of T. cruzi infections
  • Interestingly, gastrointestinal disease is much more likely to occur in the southern range of endemic Chagas disease
  • Infection most commonly involves the heart and GI tract (esophagus is most frequent site, followed by colon)
  • Far less often, other parts of the GI tract, the biliary tract and the central nervous system are affected
  • Infection is transmitted by blood sucking triatomine bugs, a type of reduviid bug that caries T. cruzi parasites
  • They become infected by biting infected mammals including humans
  • They multiply in the midgut as epimastigotes, a distinct type of flagellate; in the hindgut they transform into infective metacyclic trypomastigotes
  • People are bitten on the face and the insect defecates
  • Infection occurs when feces containing trypomastigotes reaches mucous membrane or skin abrasions, often wiped into the wound or conjunctiva by the host's hand
  • An inflammatory lesion at the site of infection is known as a chagoma
  • Parasites invade several types of host cell, transform into amastigotes and multiply in the cytoplasm
  • Amastigotes differentiate into trypomastigotes and subsequently the cell ruptures
  • Parasites spread hematogenously or invade tissues especially muscle
  • They alternate between intracellular and swimming forms in blood
  • Acute infection sometimes is associated with acute illness, usually with mild nonspecific symptoms, although rarely severe or even fatal disease may occur
  • Reactivation of infection in the setting of immunosuppression may lead to severe disease
  • Chronic Chagas disease occurs in 10 - 30% of infected individuals years or even decades after initial infection, most commonly involving the heart, less likely the gastrointestinal tract
  • Cytotoxic T cells invade ganglia, causing reduced numbers of interstitial cells of Cajal, leading to parasympathetic denervation with reduced and eventual failure of relaxation of anal sphincters during defecation
  • In some cases the inflammatory response may be contained by enteric glial cells (Hum Pathol 2009;40:244)
Diagrams / tables

Images hosted on other servers:

Life cycle

Clinical features
  • Infection may occur from blood transfusion or organ transplantation and there are rare reports of transmission from contaminated food or laboratory accidents
  • In a minority of cases, acute disease occurs that may be lethal due to cardiac or neurologic complications
  • Infection is lifelong without treatment
  • Most infected subjects remain in an asymptomatic indeterminant phase but 10 - 30% develop cardiac or gastrointestinal tract complications
  • Parasite invades the bowel wall and damages the enteric nervous system leading to megacolon
  • Patients with chagasic megacolon suffer from chronic constipation and abdominal pain; in severe cases, there may be several weeks between bowel movements
  • Chronic disease manifests years or even decades after initial infection
    • Fecalith / fecaloma may develop
    • Acute obstruction may occur, possibly with volvulus and lead to perforation
    • Toxic megacolon may occur
  • Acute disease may be diagnosed by review of a peripheral blood smear; however, other laboratory methods are necessary to diagnosis chronic Chagas disease
  • Serologic diagnosis by enzyme linked immunosorbent, immunofluorescence or chemiluminescence methods
  • Equivocal serologic tests may be confirmed with PCR based testing but this lacks sensitivity for detecting chronic disease
  • False positives may occur; the WHO recommends confirmation with a different format assay
Radiology description
  • Megacolon with contraction of anal sphincter
  • Lengthening of the distal colon
Prognostic factors
  • Immunosuppressed patients may suffer from severe disease
Case reports
  • Early / mild cases are treated with high fiber diets, laxatives, stool softeners and enemas
  • With more severe disease, manual disimpaction may be necessary
  • In children, endoscopic emptying may be employed
  • Toxic megacolon and volvulus are treated surgically and surgical intervention may be considered for patients with severe chronic disease
  • Antiparasitic treatment has a high failure rate and potentially toxic side effects
  • Acute infection and children under 18 are usually treated
  • Whether to treat indeterminant or chronic symptomatic infection is controversial
  • Nifurtimox and benznidazole are available from the CDC
Clinical images

Contributed by Bobbi Pritt, M.D., Nicole L. Achee, Ph.D. and John P. Grieco, Ph.D.

Triatomine bugs

Microscopic (histologic) description
  • Ganglionitis with neuronal cell depopulation
  • Fibrosis and mast cell infiltrates are also present
Microscopic (histologic) images

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Missing Image

Blood smears

Differential diagnosis
Board review style question #1
    Which statement is true?

  1. Chronic Chagas disease most commonly affects the central nervous system
  2. Patients with acute Chagas disease invariably progress to chronic disease
  3. The incidence of Chagas disease is increasing
  4. The majority of individuals infected with T. cruzi spontaneous clear the parasite
  5. Vector borne transmission of Chagas disease only occurs in the Western hemisphere
Board review style answer #1
E. Vector borne transmission only occurs in the Western hemisphere. Chagas disease is endemic in all of the continental Americas south of the United States but it does not occur in the Caribbean. Vector borne transmission in the southern United States is documented but is rare. Imported cases occur worldwide. Infection is life long but only 10 - 30% of individual who are infected will progress to chronic disease that most commonly affects the heart, followed by the esophagus, then the colon. The infection is transmitted by blood sucking triatomine bugs, a type of reduvid bug that caries T. cruzi parasites. Triatomine bugs are more likely to be found in conditions that occur in dilapidated housing; public health campaigns to improve housing as well as screening of donated blood has resulting in decreasing numbers of new infections over time.

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Reference: Chagas disease (trypanosomiasis)
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