Two main form of this protozoal disease are recognised - African trypanosomiasis (sleeping sickness) and American trypanosomiasis (Chagas' disease).

African Trypanosomiasis

Two forms of African trypanosomiasis, or sleeping sickness, are seen -

1. Trypanosoma gambiense in West Africa and
2. Trypanosoma rhodesiense in East Africa.

Both types are spread by the tsetse fly. Trypanosoma rhodesiense tends to follow a more acute course.

Clinical features include:

• Trypanosoma chancre - painless subcutaneous nodule at site of infection
• intermittent fever
• enlargement of posterior cervical lymph nodes (Winterbottom's sign)
• later: central nervous system involvement e.g. somnolence, headaches, mood changes, meningoencephalitis

Management

• early disease: IV pentamidine or suramin
  • IV pentamidine is also used in Pneumocystis jirovecii pneumonia, and leishmaniasis
  • Suramin does not cross BBB effectively and is therefore not used when there is CNS involvement.
  • Suramin can cause significant adverse effects including nephrotoxicity, peripheral neuropathy, and hypersensitivity reactions.
• later disease or central nervous system involvement: IV melarsoprol
  • highly toxic arsenical compound associated with severe adverse effects including encephalopathy, which occurs in approximately 5-10% of patients

Chagas Disease

American trypanosomiasis, or Chagas' disease, is caused by the flagellated protozoan Trypanosoma cruzi.

Vector: Triatomine bugs (also known as "kissing bugs") transmit the parasite to humans and animals.

Reservoir hosts: Wild and domestic animals, such as dogs, cats, rodents, and opossums.

The vast majority of patients (95%) are asymptomatic in the acute phase although a chagoma (an erythematous nodule at site of infection) and unilateral painless periorbital oedema (aka Romaña sign) are sometimes seen. Chronic Chagas' disease mainly affects the heart and gastrointestinal tract