Parasite

Chagas Disease

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Chagas Disease, American Trypanosomiasis, Trypanosoma cruzi, Rowana's Sign

  • Epidemiology
  1. Endemic Regions (tropical Americas)
    1. Mexico
    2. Central America
    3. South America
  2. Prevalence (estimated)
    1. Endemic regions: 8-11 Million infected
    2. United States: 300,000 infected
      1. Most cases are via immigration and travel
      2. However vector-borne transmission has occurred in U.S.
      3. Bern (2011) Clin Microbiol Rev 24(4): 655-81 [PubMed]
  • Pathophysiology
  1. Organism
    1. Parasite: Trypanosoma cruzi
  2. Transmission: Vector borne (primary source)
    1. Triatomine bug (reduviid bug, assassin bug or kissing bug) is an Insect that feeds on blood
      1. Triatomine bugs nest in the crevices of mud and clay houses
      2. Triatomine bugs are nocturnal and feed on humans as they sleep
      3. Acquires T. cruzi via ingested blood containing the Parasite as trypomastigote
      4. Trypomastigotes differentiate inside the Insect midgut into epimastigotes which further multiply
      5. Epimastigotes differentiate into the infective form, metacyclic trypomastigotes
    2. Insect carrying the Parasite defecates into a human wound site or mucous membranes (e.g. Conjunctiva)
      1. Parasite is initially transmitted from Insect to human as metacyclic trypomastigote
      2. Metacyclic trypomastigotes differentiate into amastigotes on human cell penetration
      3. Amastigotes multiply via binary fission releasing trypomastigotes to infect other human cells
  3. Transmission: Other mechanisms
    1. Congenital (vertical transmission)
    2. Blood Transfusion
    3. Organ transplant
    4. Contaminated food
    5. Lab exposure
  • Findings
  • Acute Phase
  1. Lasts for 4-8 weeks after infection
  2. Localized Edema at the bite site
  3. Often asymptomatic
  4. Rowana's Sign (20-50% of acute cases)
    1. Painless unilateral eye swelling
  5. Non-specific febrile illness (variably present)
    1. Malaise
    2. Headache
    3. Anorexia
    4. Non-pruritic rash
    5. Persistent Sinus Tachycardia
  • Findings
  • Chronic Phase
  1. Onset weeks to months after infection
  2. Life-long infection until treated
  3. Asymptomatic in 70-80% of cases
  4. Serious chronic manifestations occur in 20-30% of cases
    1. See Complications below
  • Complications
  1. Cardiac
    1. Conduction abnormalities
    2. Apical aneurysm
    3. Congestive Heart Failure
    4. Thromboembolism
    5. Peroicardial effusion
  2. Gastrointestinal
    1. Megaesophagus
    2. Toxic Megacolon
  3. Neurologic
    1. Cerebrovascular Accident risk
  4. Infants with congenital infection (vertical transmission from mother)
    1. Often asymptomatic
    2. IUGR with low birth weight in some cases
    3. Anemia
    4. Thrombocytopenia
    5. Hepatomegaly
    6. Splenomegaly
    7. Myocarditis (rare)
    8. Meningoencephalitis (rare)
  • Labs
  1. Acute infection
    1. Peripheral Smear (Light Microscopy)
      1. Peripheral blood (or anticoagulated cord blood) for trypomastigotes
    2. Polymerase chain reaction (PCR)
      1. Highly specific and may be positive before Peripheral Smear demonstrates organisms
  2. Chronic infection
    1. Organism counts too low in chronic disease to be detectable by Peripheral Smear or PCR
    2. Serology tests for T. cruzi
      1. Positive on at least two different serologic tests
      2. Enzyme-linked immunosorbent assay (ELISA)
      3. Immunofluorescent Antibody assay
    3. Adjunctive diagnostic modalities
      1. Echocardiogram (for Heart Failure)
      2. Electrocardiogram (for arrhythmia)
      3. Upper endoscopy (for megaesophagus)
  • Diagnostics
  1. Electrocardiogram
    1. Obtain at time of diagnosis and as needed
  • Management
  • Antiparasitic
  1. Protocol
    1. Treat immediately if not contraindicated
    2. Course of antiparasitic agent treatment is 60-90 days
  2. Contraindications to antiparasitic therapy
    1. Pregnancy
    2. Severe hepatic insufficiency
    3. Severe Renal Insufficiency
  3. Indications: Acute Chagas Disease
    1. Treat all acute Chagas Disease cases (if not contraindicated)
    2. Treat congenitally acquired Chagas Disease
    3. Treat immunocompromised patients with reactivated Chagas Disease
  4. Indications: Chronic Chagas Disease
    1. All patients under age 18 years old with chronic Chagas Disease
    2. Patients under age 50 years old with chronic Chagas Disease and no advanced Cardiomyopathy
    3. Consult CDC or infectious disease for management recommendations regarding specific case management
  5. Preparations (available in U.S. through CDC)
    1. As noted above, both approved agents are contraindicated in pregnancy and severe renal or liver dysfunction
    2. Only two agents have proven efficacy
      1. Benznidazole
      2. Nifurtimox
  6. Adverse effects
    1. Weight loss
    2. Anorexia
    3. Polyneuropathy
  • Management
  • Complications
  1. Congestive Heart Failure
    1. See Congestive Heart Failure Exacerbation Management
    2. Exercise caution with Beta Blockers (higher risk of Bradycardia)
  2. Atrial Arrythmias
    1. Cardiac Pacemaker (Heart Block, Sick Sinus Syndrome)
  3. Ventricular Arrhythmias
    1. Amiodarone
    2. Catheter ablation and placement of IACD
  4. Thromboembolism risk
    1. Consider antithrombotic therapy
  • Screening
  1. Children of mothers with Chagas Disease
  • Prevention
  1. Blood donors in the United States are screened for T cruzi (since 2007)
    1. Not allowed to donate blood if positive
  2. Endemic area strategies
    1. Clean rooms
    2. Mosquito nets
    3. Insecticides
  • Resources