19 Chagas Disease

Jo 18/09/18

Trypanosoma cruzi

Multiple names for the vector the bug

Chagas spread and HAT spread very similar. COlonial power (portugeuse) decided to cut a railline into the forest. Conscripted workers would die of a lot of things, including myocarditis, from chagas disease. A doctor was hired (Carlos Chagas) to treat people, he found inexplicable deaths from sudden cardiac death. He realised that children were being bitten by a parasite in the night.

Chagas found the trypanosomes.

Chagas parasites curl up when HAT are open and loose.

19.1 Epidemiology

Traditionally rural over south america. But there is a high potential for urban spread (but it usually does not)

Burden of disease is clear, it has significant impact in disability adjusted life years in latin america, the highest of any parasitic illness.

People are usually infected as children (10% mortality), then chonic 30% will get heart failure as an adult.

300,000 prevelance in USA, 122000 in europe. Maybe 10% of those will have cardiac failure (double check with moodle slides)

19.2 Life Cycle

The main difference with HAT is this is an intracellular pathogen, not extracellular.

It infects cells of autonomic nervous system, particullarly around heart and gut.

19.3 Acute Disease

Chancre - Romana’s Sign - at site of bite

Can trigger a major immunological reaction (papudos)

GET MORE FROM SLIDES

19.4 Chronic Disease

Attacks heart or intestines

If you biopsy the lining of the heart of these patients you will see parasites!

Classically you get a left ventricular apical aneurysm. This could ultimately rupture, or get thrombus formation.

You also see them in the intestine. They target the auerbach plexus, leading to autonomic nerve destruction, hypomotility.

In the US there is rarely gut stuff, almost exclusively cardiac stuff.

19.5 Immunology

This disease is controlled by cell mediated immunity. You can get “chagomas” in the central nervous sytem when you have CMI failure (HIV, chemotherapy)

19.6 Diagnosis

PCR - if you have access, do it

If you’re somewhere without PCR, you could always do a blood film. But the negative predictive value declines over time, so it’s less usefull for chronic.

Xenodiagnosis - get the patient rebitten, see if you get bugs in the bugs!

19.7 Management

Acute - definitely treat!

Same with congenital infection

Indeterminate infection? (Seropositive but feel fine) - Probably treat. More difficult to know, especially if PCR negative

Chronic infection. You really need to focus on the cardiac and GI symptoms. But you would treat as it slows the progression of disase.

19.7.1 Drugs

Are really bad

Nifurtimox - toxic and doesn’t really work that well.

Same with Bend

Posaconazole was promising but really not good in humans and hyperexpensive

19.8 Prevention

Aggressive housing investments, spraying roofs