week 8

• Hemoflagellates


  Flagellates that invade the blood
• Four developmental forms of hemoflagellates

  • Amastigote, Promastigote, Epimastigote, Trypomastigote
• Amastigote (Leishmania form)


  • No flagella, only intracellular stage found in the tissue of the human
  • Oval with single nucleus
  • Found in tissue muscles and CNS with macrophages

  
• The Trypanosomes


  • Trypanosoma brucei gambiense
  • Trypanosoma brucei rhodisiense
  • Trypanosoma cruzi
  • Trypanosoma rangeli
• African Trypanosomes (Trypansoma brucei complex)


  • Exhibits only epimastigote and trypomastigote forms
  • Undulating membrane is stained blue
  • Flagellum is stained red and runs along the edge of the undulating membrane
• Trypanosoma brucei gambiense


  Found in West and Central Africa, causes Gambian Sleeping Sickness

  
• Sleeping sickness is when the parasite reaches the brain, the patient would fall down to sleep as it affects the CNS

  
• Life cycle of African Trypanosomes

  1. Human host gets infection through blood meal from infected tsetse fly

  2. Metacyclic trypomastigotes inoculated into host and transform into Bloodstream trypomastigote

  3. Bloodstream Trypomastigotes multiply in lymph, spinal fluid, blood

  4. Bloodstream Trypomastigotes recovered from blood for diagnosis

  5. Tsetse fly takes in trypomastigotes from infected host

  6. Procyclic trypomastigotes develop in tsetse fly

  7. Epimastigotes multiply in salivary gland

  8. Metacyclic trypomastigotes develop in tsetse fly

  
• Life cycle of African Trypanosomes

  • Vector: Glossina fly (tsetse fly)
  • Portal of Entry: Skin
  • Mode of Transmission: Through vector's bite
  • Infective Stage: Metacyclic trypomastigote
  • Diagnostic Stage: Blood trypomastigote
  • Habitat in human: reticular tissues of lymph and spleen, CSF

  
• Trypanosomes multiply by binary fission (asexual)
• Sleeping sickness


  • Invades the CNS, can be mild to severe, acute and chronic
  • Rhodesian trypanosomiasis is more rapid and fatal, also damages tissues like kidney and myocardium

  
• Diagnosis of African Trypanosomes

  1. Giemsa-Wright's stained blood smear to demonstrate trypomastigotes

  2. Serological tests like IHAT, IFAT, ELISA to detect antibodies
• Treatment of African Trypanosomiasis

  Eflornithine for Gambian case, Pentamidine and suramin for cases that do not reach CSF
• Trypanosoma cruzi (American Trypanosome)


  Causes Chagas' disease or American trypanosomiasis, an intracellular parasite exhibiting 4 developmental stages

  
• Amastigotes of T. cruzi

  • Round/ovoid with single nucleus, found in small groups in tissues, multiply through binary fission in the RES
• Life cycle of Trypanosoma cruzi

  1. Triatomine bug (Reduviid bug) takes blood meal and passes metacyclic trypomastigotes in feces

  2. Metacyclic trypomastigotes enter through bite wound or mucous membranes

  3. Metacyclic trypomastigotes transform into amastigotes in tissue cells

  4. Amastigotes multiply by binary fission

  5. Amastigotes transform back into trypomastigotes which can be taken up by another Reduviid bug

  6. Trypomastigotes transform into epimastigotes in Reduviid bug

  7. Epimastigotes multiply and transform into metacyclic trypomastigotes in Reduviid bug

  
• Life cycle of Trypanosoma cruzi

  • Vector: Triatomine bugs (Triatoma, Rhodnius, Panstrongylus)
  • Mode of Transmission: Through vector's feces entering through scratched skin or mucous membranes
  • Infective Stage: Metacyclic Trypomastigote
  • Habitat In human: RES and bloodstream
  • Multiply by Binary fission

  
• Chagoma


  Small, painful reddish nodule at the site of inoculation
• Treatment of Chagas disease

  Nifurtimox and benzonidazole, partially effective for acute cases

  
• Vector


  Triatomine bugs (also known as Triatoma, Rhodnius, Panstrongylus) (commonly known as kissing bug)
• Mode of Transmission


  Through a vector (Infective stage is passed out in the bug's feces → gains entrance to host (scratched skin or through mucous membranes that are rubbed carrying the bug's feces))

  
• Infective Stage


  Metacyclic Trypomastigote
• Habitat In human


  RES and bloodstream
• CHAGOMA


  Small, painful reddish nodule, Inflammation on the site of inoculation
• ROMANA'S SIGN


  Edema of the eyelid
• Chronic Disease

  No characteristic symptoms for 20 years or more, Manifestations: megaesophagus, megacolon, cardiospasm, cardiomyopathy related to congestive heart failure
• Chagas disease is serious and often fatal among young patients

  
• Treatment of Cases


  Nifurtimox and benzonidazole (Partially treatment of acute cases)
• Vector Control


  Bitting sites are cracking of the wall, Insecticides, screens, housing improvement to reduce breeding sites of bugs
• Giemsa Wright Stained (Romanowsky Stained)

  Demonstration of trypomastigotes, Samples used: Blood, Lymph node aspirate, CSF
• Xenodiagnosis


  Bugs are allowed to feed on suspected patients, Sacrifice the bug

  
• ECG


  Patients generally shows cardiac symptoms
• Serological Test


  IHAT, IFAT, ELISA, CFT
• PCR


  Amplifying the DNA from kinetoplast, To check if it is really case of T. cruzi
• Trypanosoma rangeli


  Found in areas where T. cruzi is present, Life cycle: similar to T. cruzi (vector is Reduviid bug; Rhodius sp.), Trypomastigotes are present in the blood throughout the infection, Infected patients are generally asymptomatic and do not demonstrate evidence of illness, Diagnosis: serological test & PCR, Treatment: similar to T. cruzi

  
• Two spp of African

  • Trypanosoma brucei gambiense
  • Trypanosoma brucei rhodisience
• Two spp of American

  • T. Cruzi
  • T. rangeli
• Leishmania sp


  Found in Africa, Eastern Europe and South and Central America, An intracellular flagellate that live inside the macrophages (Amastigotes), Promastigotes (Infective stage) – found in the midgut and proboscis of the vector

  
• Life Cycle of Leishmania

  1. The vector (sandfly) takes a blood meal

  2. Infective stage: Promastigote

  3. Sandfly delivers promastigote

  4. Promastigote are phagocytized by the macrophages

  5. Promastigote transform into amastigote inside the macrophages

  6. Amastigotes multiply

  7. When Sandfly bites again the infective host, it takes amastigote

  8. Ingestion of parasitized cell

  9. Amastigotes transform into promastigote stage in midgut

  10. In the digestive tract of the sandfly, promastigote transform into promastigote

  11. Divides thru binary fission migrate from the midgut to the proboscis and it is ready to infect again

  
• Vector


  Phlebotomus spp. (Sandfly)