Blood and Tissue Protozoa

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Human African Trypanosomiasis

  • Main risk is in the Savanna, open country around streams
  • Tsetse flies do not react to mosquito repellants
  • They are about the size of a deer fly.
  • The Winterbottom sign is a good sign of Gambian parasitaemia trypanosomite
  • T. bruce gambienes has an undulating tail and membrane which looks like no other

American Trypanosomiasis (Chagas disease)

  • caused by flagellated protozoan parasites that belong to the T. brucei complex
  • transmitted to humans by large, non-painful bites from tsetse flies
  • In the acute stage, death occurs in 5-10% of infants
  • Often observed as a swelling around the eye
  • The eye swells in the "Romanis sign"
  • later, glandular swelling is observed
  • If camping in Central or Southern America, use an insect proof tent.
  • Differences with African Trypanosomiasis:
    1. Found in Latin America
    2. Thicker and more C-shaped
  • Xenodiagnosis is used for American Trypanosomiasis
  • use a bug to take blood from the patient
  • Check bug after 4-6 weeks
  • If it was originally uninfected, it was a perfect environment for reproduction
  • even 1-2 trypanosomes would reproduce sufficently to be observable


  • Cats get this commonly in nature
  • domesticated cats tend to be OK because they don't get it from any "prey" per se
  • Wild cats that develop immunity shed for a time before becoming resistant
  • Infection spread to humans can be prevented by frequent change of cat litter if the cat has been outside
  • Cysts can be found in cat faeces and need days to embryonate before becoming infectious
  • Old, dried-out cat poo is a resevoir for infection
  • Could cause miscarriage


  • Tropical disease
  • also found in Europe (e.g., Italy, Sicliy and Malta)
  • Produces tremendous splenomegaly (called "Kala-azar") that takes up the entire abdomen
  • There are two phases in the lifecycle: insect and host
  • Whenever sexual reproduction takes place in one host, the asexual cycle takes place in the other organism
  • The mosquito is the definitive host


  • Relatively rare
  • Febrile symptoms that generally resemble Malaria
  • One tick bite can have Lyme disease, babesiosis, and tick paralysis