Chagas disease

see also:

• parasites

• Chagas disease (aka American trypanosomiasis) is a chronic, indolent infection by the flagellate parasite Trypanosoma cruzi which may cause serious cardiac disease many years after it was acquired
• 1st described in 1909 by the Brazilian physician and epidemiologist Carlos Chagas
• it is thought Charles Darwin may have been infected in 1835 while he was east of the Andes near Mendoza.

• some 300,000 people in US and Spain and 6.6 million people in central or southern America are thought to have this condition, most acquired in central or southern America from Mexico to Argentina with relative sparing of most parts of Brazil, and cause 8,000 deaths pa
• infection occurs when infected blood sucking tropical kissing bugs (a triatomine bug) bite people while they sleep, often near their mouths and then people scratch the site and allow contaminated bug faeces into the scratch
• rarely, infection may be acquired from breast milk, transplacental, blood transfusions or organ transplants, or even by eating contaminated food such as fruit juice
• 8-40% of opossums, raccoons and armadillos in the US are infected but only a handful of cases of the disease being acquired by people in the US

• may be subclinical
• may cause local swelling at the bite site with fevers, headaches, LN, myalgias, rash, anorexia, N/V/D and usually resolve within 3-8 weeks
• may have Romaña's sign:
  • swelling of the eyelids on the side of the face near the bite wound or where the bug faeces were deposited or accidentally rubbed into the eye
• it may be severe in the immunocompromised
• rarely, acute phase may be fatal due to myocarditis or meningoencephalitis

• this commences 8-12 weeks after the bite whether or not treatment has been given
• 60-70% never develop sysmptoms - called indeterminate chronic Chagas disease
• 30-40% develop long term issues called determinate chronic Chagas disease - often presenting 10-30yrs after the infection such as:
  • 20-30% develop dilated cardiomyopathy, cardiac aneurysms and congestive cardiac failure
  • 10% develop an mega-oesophagus (may cause secondary achalasia) or megacolon and severe weight loss
  • 10% develop neuritis that results in altered tendon reflexes and sensory impairment
  • some will develop dementia, chronic encephalopathy and neural deficits

• insect nets
• insecticides
• screening blood for blood transfusion
• as of 2018, a vaccine is being tested for human use

• early infective stages, one may find the parasite in blood under a microscope
• later stages require detecting raised serum antibodies for T. cruzi

• early infections
  • benznidazole
  • nifurtimox
  • both of the above cause skin disorders, brain toxicity, and digestive system irritation in up to 40%
  • cure becomes less likely with delay in starting Rx
• chronic phase
  • symptomatic supportive care
  • this has become a major cost in the US of some $1b pa spent on pacemakers, etc as a result of this condition
  • global cost is some $7b pa