231.1 ð é«åžçç
231.1.0.1 ð äžé éé»
231.1.0.1.1 Microbiology + Vector
- Pathogen: Trypanosoma cruzi (single species, multiple discrete typing units DTU I-VI)
- Vector: Triatomine bug (âkissing bugâ, âvinchucaâ); Triatoma infestans in Southern Cone (main); T. dimidiata, Rhodnius prolixus others
- Reservoir: dogs, opossums, armadillos, raccoons, etc. (many sylvatic + domestic mammals)
231.1.0.1.2 Transmission
- Vectorial: triatomine bug feces (NOT bite directly â bug bites and defecates near; rubbing feces into bite wound or mucous membrane transmits)
- Transfusion: major in Latin America historic; now screened
- Vertical: 5-10% of pregnancies in chronically infected mothers
- Oral: contaminated food/juice with bug feces (açaà outbreaks)
- Organ transplant from infected donor
- Lab exposure: rare
231.1.0.1.3 Epidemiology
- 6-7 million chronic infections globally (WHO)
- Endemic Latin America: Bolivia (highest), Argentina, Brazil, Mexico, others
- Increasing in non-endemic (migration): USA (300,000+), Spain, Italy, Japan, Australia
- 30% of chronic develop cardiomyopathy + GI complications
231.1.0.1.4 Clinical Stages
231.1.0.1.4.1 Acute (Weeks-Months Post-Exposure)
- 1-2 weeks incubation
- Usually mild / asymptomatic (75-95%)
- Sometimes:
- Romaña sign: unilateral painless periorbital edema + conjunctivitis (eye inoculation)
- Chagoma: erythematous nodule at skin inoculation site
- Fever, malaise, lymphadenopathy, hepatosplenomegaly
- Rare: myocarditis, meningoencephalitis (especially pediatric / immunocompromise)
- High parasitemia
- Self-limited; 100% become chronic without treatment
231.1.0.1.4.2 Indeterminate (Chronic Asymptomatic)
- Years to decades
- ~ 60-70% of chronic patients remain in this stage
- Antibodies + low parasitemia
- ECG + echo normal
231.1.0.1.4.3 Chronic Cardiomyopathy (30%)
- Decades after acute
- Conduction abnormalities (RBBB + LAFB + bradyarrhythmias) â earliest
- Dilated cardiomyopathy + congestive heart failure
- Apical aneurysms of LV (characteristic)
- Mural thrombus + embolic stroke
- Sudden cardiac death (ventricular tachycardia / fibrillation)
- Mortality: leading cause of death in endemic areas
231.1.0.1.4.4 Chronic Digestive (Megacolon / Megaesophagus)
- 10-20% chronic in Brazil + Southern Cone (geographic variation)
- Less common Mexico + Central America (different DTU)
- Megaesophagus: dysphagia â progressive
- Megacolon: chronic constipation â fecal impaction â volvulus
- Mechanism: autonomic ganglia destruction
- Surgical management often required
231.1.0.1.5 Diagnosis
231.1.0.1.5.1 Acute
- Blood smear (Giemsa) â trypomastigotes visible
- PCR â most sensitive in acute
- Serology (IgM) â may be delayed
- Buffy coat
231.1.0.1.6 Treatment
231.1.0.1.6.1 Drugs
- Benznidazole â first-line, ~ 60 days oral
- Nifurtimox â alternative, ~ 90 days oral
- Both target T. cruzi; less effective in chronic late disease
231.1.0.1.6.2 Indications for Treatment
- Acute infection: all (high cure rate ~ 80-100%)
- Recent infection including vertical (newborns): all
- Chronic indeterminate < 18 yr: all
- Chronic indeterminate 18-50 yr: shared decision (efficacy ~ 60-70%)
- Chronic with mild-moderate cardiomyopathy 18-50 yr: shared decision
- Chronic with advanced cardiomyopathy or > 50 yr: less benefit on outcomes (limited evidence â BENEFIT trial)
- Pre-transplant chronic chagas patient
- Pre-immunosuppression to reduce reactivation risk
- HIV/immunosuppression with reactivation â treat
231.1.0.1.7 Prevention
- Vector control (insecticide spraying + housing improvements + bed nets)
- Blood donor screening (Latin America + USA + Spain + others)
- Maternal screening + treatment of infected mothers (prevent vertical)
- Newborn screening + treatment (high cure if treated promptly)
- No vaccine yet
231.1.0.2 1ïžâ£ Microbiology + Life Cycle
231.1.0.2.1 Trypanosoma cruzi
- Single species, multiple DTUs (TcI-TcVI) â different geographic + clinical patterns
- Trypomastigote (extracellular, bloodstream) + amastigote (intracellular, tissue, no flagellum) forms
231.1.0.2.2 Life Cycle
- Triatomine bug bites human + defecates near wound
- Scratching rubs feces into wound or mucous membrane â trypomastigotes enter
- Trypomastigotes invade host cells (cardiac, GI, etc.) â become amastigotes
- Amastigotes multiply intracellularly
- Cell rupture â trypomastigotes released into bloodstream
- Bug takes blood meal â ingests trypomastigotes
- Multiply in bug â trypomastigotes in feces
231.1.0.3 2ïžâ£ Acute Chagas
231.1.0.3.2 Clinical Features
231.1.0.3.2.1 Skin Inoculation
- Chagoma: erythematous nodule at bite site
- Usually transient
- May go unnoticed
231.1.0.3.3 Severity
- Mostly self-limited
- Mortality < 5% in acute (typically severe myocarditis or meningoencephalitis)
- 100% develop chronic without treatment
231.1.0.4 3ïžâ£ Chronic Chagas
231.1.0.4.1 Indeterminate Stage
- Years-decades asymptomatic
- ~ 60-70% of chronic patients remain here lifelong
- ECG + echo normal
- Serology persistently positive
- Low parasitemia (PCR may be negative or low)
231.1.0.4.2 Chronic Cardiomyopathy (~ 30% Develop)
231.1.0.4.2.2 Clinical Stages (Modified Mexican Consensus 2024)
- Stage A (Indeterminate): serology + only
- Stage B1: ECG abnormalities (RBBB, LAFB), normal echo
- Stage B2: echo abnormalities (LVEF preserved), conduction abnormalities
- Stage C: HF symptoms + reduced LVEF
- Stage D: refractory HF, advanced
231.1.0.5 4ïžâ£ Diagnosis Chronic Chagas
231.1.0.5.1 Serology (2 Tests Required)
- Indirect Hemagglutination (IHA)
- ELISA
- IFA
- Recombinant antigen tests
- Discordant â 3rd test
- WHO standard
231.1.0.5.2 PCR
- Variable sensitivity in chronic (low parasitemia)
- Useful for:
- Acute reactivation
- Vertical transmission monitoring
- Post-treatment monitoring
231.1.0.6 5ïžâ£ Treatment Chronic Chagas
231.1.0.6.1 Goal
- Reduce parasite burden
- Prevent / slow progression
- BENEFIT trial 2015: benznidazole vs placebo in established cardiomyopathy
- PCR negativization improved with drug
- No mortality benefit in advanced chronic CM
- Most benefit in early chronic before cardiomyopathy develops
231.1.0.6.2 Treatment Indications
| Population | Treat? |
|---|---|
| Acute infection | Yes (cure ~ 80-100%) |
| Recent infection (incl vertical newborn) | Yes |
| Chronic indeterminate < 18 yr | Yes (efficacy higher in younger) |
| Chronic indeterminate 18-50 yr | Shared decision (efficacy 60-70%) |
| Chronic mild-moderate cardiomyopathy 18-50 yr | Shared decision |
| Advanced cardiomyopathy or > 50 yr | Limited mortality benefit (BENEFIT trial) |
| HIV / Immunosuppression / Pre-immunosuppression | Yes (prevent reactivation) |
| Pre-organ transplant | Yes |
| Reactivation | Yes |
| Pregnancy + newborn | Treat newborn, not pregnant; postpartum mother |
231.1.0.7 6ïžâ£ Reactivation in Immunocompromise
231.1.0.7.1 Risk Factors
- HIV + low CD4 (< 200; especially < 100)
- Organ transplant (immunosuppression)
- Anti-TNF (rheumatologic, IBD)
- Chemotherapy
- Steroid high-dose long-term
231.1.0.7.2 Clinical
- Severe acute-like presentation
- Myocarditis (acute)
- Meningoencephalitis (severe, often fatal)
- Skin nodules
- High parasitemia
231.1.0.8 7ïžâ£ Prevention + Public Health
231.1.0.8.1 Vector Control
- Insecticide spraying indoor (deltamethrin)
- Housing improvement (plaster walls, replace thatched roofs)
- Bed nets in some settings
- Southern Cone Initiative â eliminated vector transmission in some areas
231.1.0.8.2 Blood Donor Screening
- Latin America countries since 1990s
- USA mandatory since 2007
- Reduces transfusion-transmitted dramatically
231.1.0.8.3 Maternal Screening
- WHO recommendation: all pregnant women from endemic areas
- Treat seropositive postpartum (not during pregnancy)
- Newborn screening + treat if positive
231.1.0.8.5 Travelers
- Avoid sleeping in adobe/thatched-roof structures in endemic
- Insecticide treated bedding