Chagas

Question 1

Chagas - organism

Answer 1

Trypanosomi cruzi
Parasitic protozoa causing American Trypanosomiasis [Chagas disease]

Question 2

Chagas - lifecycle

Answer 2

Triatomine bug takes a blood meal - passes metacyclic trypomastigotes in faces
Metacyclic trypomastigotes penetrate various cells at bite wound site. Inside cells they transform into amastigotes
Amastigotes multiply in cells - transform into trypomastigotes and burst out of cell into bloodstream
These can infect other cells or be ingested by triatomine blood meal
In the triatomine bug - epimastigoes in midgut - multiply in midgut and become metacyclic trypomastigoes in hindgut

Question 3

Chagas - vector transmission

Answer 3

Triatomine bugs [assassin bug] - triatoma infestans, rhodnius prolixus, triatonia dimidiata
-Faeces enter bite wound
-Oral ingestion of bug

Question 4

Chagas - non-vector transmission

Answer 4

-Blood transfusion
-Contaminated food
-Mother to child

Question 5

Chagas - vertical transmission

Answer 5

Born to T cruzi seropositive mother and either:
-Parasites identified at birth - PCR, microhaematocrit
OR
-T cruzi Ab persistence >9 months

Presentation: 50-90% asymptomatic
Premature, LBW, HSmegaly, meningoencephalitis

Treatment: early treatment of newborn [anti-parasitic treatment contraindicated in pregnancy]

Question 6

Chagas - clinical features

Answer 6

Symptomatic acute infection rare:
-Usually self-limiting 4-8 weeks
-Fever, malaise, lymphadenopathy, HSmegaly, myocarditis
-Rare: meningoencephalitis, orbital cellulitis [Romana’s sign]

Cardiac disease: chagas cardiomyopathy
-Arrythmias - SN dysfunction,AV block, RBBB +/- L anterior fascocular block, PVCs, VT, AF
-Segmental wall motion abnormalities, dilated CM
-Aneurysm, thromboembolism risk

Digestive disease:
-Oesophageal dysmotility, and megaoesophagus
-Colonic dysmotility and mega-colon
Presents with constipation and swallowing difficulty
[GI symptoms more common south of Amazon - TcII and TcV]

Question 7

Chagas - T cruzi infection vs Chagas disease

Answer 7

Presumed seropositive for life
Indeterminate disease [2/3rds infection ‘silent’]:
-Lifelong seropositivity for T cruzi
-No clinical disease
-Normal life expectancy

Determinate disease - 10-40 years following exposure:
-Cardiomyopathy
-Digestive [10%]
-Cardiodigestive

Question 8

Chagas - diagnosis

Answer 8

Serology - in chronic phase
-2+ positive serology
-Positive in indeterminate phase
-ELISA, IFAT, HAI

PCR
-Only if seropositive, not sensitive enough for diagnosis
-For congenital infection and reactivation

Microscopy - only useful in acute infection and congenital

Xenodiagnosis - no longer routinely used

Question 9

Chagas - management

Answer 9

All positive patients require cardiac workup and investigation of GI disease if symptomatic

Treatment:
Beznidazole - 60 days
SE: Skin rash, peripheral neuropathy, weight loss, N+V, leukopenia, thrombocytopenia

Alternative drug:
Nifurtimox
SE: peripheral neuropathy, weight loss, N+V, leucopenia, myalgia, mood changes