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Trypanosomes

Trypanosomes. We will discuss two groups. African group (transmitted by tsetse flies belonging to the genus Glossina ) New World (transmitted by bugs). African Sleeping Sickness. The Trypanosoma brucei group. T. brucei brucei T. brucei gambiense T. brucei rhodesiense. T. b. brucei.

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Trypanosomes

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  1. Trypanosomes • We will discuss two groups. • African group (transmitted by tsetse flies belonging to the genus Glossina) • New World (transmitted by bugs)

  2. African Sleeping Sickness • The Trypanosoma brucei group. • T. brucei brucei • T. brucei gambiense • T. brucei rhodesiense

  3. T. b. brucei • Occurs in the circulatory system of most native antelopes, ruminants, and other wildlife in Africa.

  4. T. b. brucei • Occurs in the circulatory system of most native antelopes, ruminants, and other wildlife in Africa. • Non-pathogenic to these animals (does not kill them!).

  5. T. b. brucei • Occurs in the circulatory system of most native antelopes, ruminants, and other wildlife in Africa. • Non-pathogenic to these animals (does not kill them!). • However it is fatal to introduced livestock like cattle, causing a wasting disease called Nagana.

  6. Nagana caused by T. b. brucei

  7. Resistant Breeds of Cattle

  8. T. b. gambiense:Chronic or Gambian Sleeping Sickness • Occurs in people.

  9. T. b. gambiense:Chronic or Gambian Sleeping Sickness • Occurs in people. • Fatal if not treated.

  10. T. b. gambiense:Chronic or Gambian Sleeping Sickness • Occurs in people. • Fatal if not treated. • Chronic infections (low-level infection that last a long time).

  11. T. b. gambiense:Chronic or Gambian Sleeping Sickness • Occurs in people. • Fatal if not treated. • Chronic infections (low-level infection that last a long time). • Does not occur in either native animals or livestock.

  12. T. b. gambiense:Chronic or Gambian Sleeping Sickness • Occurs in people. • Fatal if not treated. • Chronic infections (low-level infection that last a long time). • Does not occur in either native animals or livestock. • It is transmitted from person to person by the Tsetse fly.

  13. T. b. rhodesiense: Acute or Rhodesian Sleeping Sickness • Causes acute infections in people.

  14. T. b. rhodesiense: Acute or Rhodesian Sleeping Sickness • Causes acute infections in people. • Usually fatal within a year.

  15. T. b. rhodesiense: Acute or Rhodesian Sleeping Sickness • Causes acute infections in people. • Usually fatal within a year. • Occurs in native animals but it is not fatal in these animals.

  16. T. b. rhodesiense: Acute or Rhodesian Sleeping Sickness • Causes acute infections in people. • Usually fatal within a year. • Occurs in native animals but it is not fatal in these animals. • Transmission by Tsetse fly.

  17. T. b. rhodesiense: Acute or Rhodesian Sleeping Sickness • A more recent colonizer of people and therefore does not do well in people and kills them.

  18. T. b. rhodesiense: Acute or Rhodesian Sleeping Sickness • A more recent colonizer of people and therefore does not do well in people and kills them. • It has not been around long enough to have adapted to its host (humans).

  19. The Vector Glossina

  20. The Vector Glossina Biology of Glossina spp.

  21. The Vector Glossina • “Host” seeking behavior: • Visual sense used to search for animal or human to feed on. • Spend most of their time resting on vegetation waiting in ambush for their prey to come into range.

  22. Stimulate feeding by uric acid, leucine, valine and lactic acid (Human Sweat).

  23. The Vector Glossina • The genus is divided into 23 species (three species groups).

  24. The Vector Glossina • The genus is divided into 23 species (three species groups). • Most of these can transmit Trypanosomes.

  25. The Vector Glossina • The genus is divided into 23 species (three species groups). • Most of these can transmit Trypanosomes. • However two species are important in the transmission to people, Glossina palpalis (T. b. gambiense) and Glossina morsitans (T. b. rhodesiense).

  26. Glossina spp. have different “host” preference!

  27. The G. morsitans group tends to feed on suids (mainly warthogs), and bovids (buffalo), less so on people.

  28. The G. palpalis group tends to feed on reptiles, and loves to feed on people.

  29. G. morsitans is a savanna species. G. palpalis is associated with rivers and lakes.

  30. Life Cycle • Only 2 stages in life cycle – Epimastigote and Trypomastigote.

  31. Trypanosoma brucei life cycle 1. Uninfected tsetse fly (Glossina) bites an infected vertebrate host and ingests trypomastigote circulating in the bloodstream.

  32. Trypanosoma brucei life cycle 1. Uninfected tsetse fly (Glossina) bites an infected vertebrate host and ingests trypomastigote circulating in the bloodstream. 2. Trypomastigotes multiply by longitudinal binary fission in fly gut. 

  33. Trypanosoma brucei life cycle 3. Trypomastigotes migrate to the salivary glands and transform into epimastigotes and multiply for several generation.

  34. Trypanosoma brucei life cycle 3. Trypomastigotes migrate to the salivary glands and transform into epimastigotes and multiply for several generation. 4. Epimastigotes transform back into Metacyclic Trypomastigotes (short stumpy forms) in the salivary glands. These form the infective stage.

  35. Trypanosoma brucei life cycle 3. Trypomastigotes migrate to the salivary glands and transform into epimastigotes and multiply for several generation. 4. Epimastigotes transform back into Metacyclic Trypomastigotes (short stumpy forms) in the salivary glands. These form the infective stage. 5. Tsetse fly bites a human or ruminant host and inoculates metacyclic trypomastigotes into bloodstream.

  36. Trypanosoma brucei life cycle 3. Trypomastigotes migrate to the salivary glands and transform into epimastigotes and multiply for several generation. 4. Epimastigotes transform back into Metacyclic Trypomastigotes (short stumpy forms) in the salivary glands. These form the infective stage. 5. Tsetse fly bites a human or ruminant host and inoculates metacyclic trypomastigotes into bloodstream. 6. Trypomastigotes live and multiply in the blood and lymph. In some cases, trypomastigotes migrate to the central nervous system.

  37. Trypanosoma brucei life cycle • For our purposes we will consider only two life cycle stages trypomastigotes in vertebrate host and epimastigote in Glossina which will be transmitted anterior station or salivarian transmission to the vertebrate host.

  38. African Trypanosomiasis Course of Infection • There are four phases. • The first two phases of trypanosomiasis only show up in people of non-African decent (Europeans).

  39. African Trypanosomiasis Course of Infection • Phase I: Incubation Period. • Trypomastigote in skin. • Red lesion and chancre at site of bite, painful. • Itching and inflammation of skin. • Duration one to two weeks.

  40. African Trypanosomiasis Course of Infection • Phase II: Trypomastigotes enter circulation. • Fever • Headache • Skin rash • Duration is variable

  41. African Trypanosomiasis Course of Infection • Phase III: Trypomastigotes collect in lymph nodes and channels. • Cells not invaded but there is proliferation of endothelial cells • Infiltration of leukocytes • Enlargement of lymph nodes

  42. Phase III Enlargement of lymph nodes in cervical triangle (on back of neck) Winterbottom’s Sign one of the cardinal signs of African Trypanosomiasis.

  43. African Trypanosomiasis Course of Infection • Phase III: Trypomastigotes collect in lymph nodes and channels. • Fever, headache, and delayed sensation to pain • General weakness • Duration many years with T. b. gambiense; less than 1 year and usually less than 4 mo for T. b. rhodesiense

  44. African Trypanosomiasis Course of Infection • Phase IV: Invasion of Central Nervous System-African Sleeping Sickness.

  45. African Trypanosomiasis Course of Infection • Phase IV: Invasion of Central Nervous System-African Sleeping Sickness. • Headaches are severe • Emaciation • Mental dullness • Apathy; disinclination to work • Drowsiness and coma • Death from asthenia, heart failure, meningitis, severe fall, etc.

  46. African Trypanosomiasis Course of Infection • Phase IV: Invasion of Central Nervous System-African Sleeping Sickness. • Duration variable with T. b. gambiense; usually does not occur with T. b. rhodesiense.

  47. Pathology 1) Parasites themselves are toxic. -Their byproducts are toxic and end up circulating in the blood steam.

  48. Pathology 1) Parasites themselves are toxic. -Their byproducts are toxic and end up circulating in the blood steam. 2) Hyper stimulated immune system. -Parasite has variable antigenic types (VATs) which are constantly changing. -This compromises our immune system, and those infected can be susceptible to other bacteria and virus infections.

  49. Pathology 3) Host lyses its own erythrocytes (RBCs). -This is why anemia is a symptom of this disease. So why does this happen?

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