Hemoflagellates

• Hemoflagellates are a group of vector-borne protozoan parasites that include Leishmania (causing leishmaniasis) and Trypanosoma (causing trypanosomiasis)
• Hemoflagellates


  • Fusiform body - spindle-shaped, tapered ends
  • Central nucleus
  • 1 anterior flagella
• Morphologic stages of hemoflagellates

  • Amastigote
  • Promastigote
  • Epimastigote
  • Trypomastigote
• Hemoflagellates do not have cyst and trophozoite stages
• Clinically significant hemoflagellates


  • Leishmania
  • Trypanosoma
• Vectors for hemoflagellates


  • Reduviid bug/Triatoma bug/Kissing bug/Triatomine bug (for Trypanosoma cruzi)
  • Glossina spp. (Tsetse fly) (for Trypanosoma brucei)
  • Phlebotomus spp. (Sandfly) (for Leishmania spp.)
• Amastigote


  Oval shaped, no special characteristics
• Promastigote


  Has a flagellum
• Epimastigote


  Has a flagellum and an undulating membrane
• Trypomastigote


  Has a flagellum, an undulating membrane, and granules
• Axoneme provides structural support, basal body provides energy, and kinetoplast contains mitochondrial DNA in hemoflagellates
• Clinically significant Trypanosoma species

  • Trypanosoma cruzi (American Trypanosomiasis)
  • Trypanosoma brucei (African Sleeping Sickness)
  • Trypanosoma brucei gambiense (West African Sleeping Sickness)
  • Trypanosoma brucei rhodesiense (East African Sleeping Sickness)
• Mode of transmission for Trypanosoma


  Insect bite, insect feces contaminate the wound
• Infective stage for Trypanosoma


  Metacyclic Trypomastigote
• Diagnostic stage for Trypanosoma


  Trypomastigote (in blood films)
• Morphological stages of Trypanosoma cruzi in human host


  • Amastigote
  • Trypomastigote
• Amastigote stage of Trypanosoma cruzi


  Found intracellularly, stage that multiplies inside host tissues such as cardiac muscle and brain
• Trypomastigote stage of Trypanosoma cruzi


  Found in peripheral blood, has characteristic C or U shape
• Mode of transmission for Trypanosoma cruzi

  Insect bite, blood transmission, congenital transmission, kidney transplantation
• Infective stage for Trypanosoma cruzi


  Metacyclic Trypomastigote found in bug excreta
• Diagnostic stage for Trypanosoma cruzi


  C or S shape Trypomastigote
• Life cycle of Trypanosoma cruzi

  1. Triatomine bug bites host

  2. Bug defecates on open wound, releasing metacyclic trypomastigotes

  3. Metacyclic trypomastigotes enter bloodstream and transform into amastigotes

  4. Amastigotes multiply inside host cells

  5. Amastigotes transform into trypomastigotes and burst out of cells

  6. Trypomastigotes either invade new tissues or remain in bloodstream

  7. Trypomastigotes ingested by triatomine bug

  8. Trypomastigotes transform into epimastigotes in bug's digestive tract

  9. Epimastigotes multiply and transform into metacyclic trypomastigotes in bug's hindgut

  10. Cycle repeats
• Chagas disease/American Trypanosomiasis


  Caused by Trypanosoma cruzi, characterized by organ enlargement (cardiomegaly, megaesophagus, megacolon)
• Chagoma


  Reddish lesion due to proliferation of Trypanosoma cruzi
• Acute Chagasic Meningoencephalitis


  High levels of CSF albumin due to presence of Trypanosoma cruzi amastigotes in neuronal tissue
• Laboratory diagnosis methods for Trypanosoma cruzi

  • Blood examination (Giemsa-stained blood films)
  • Machado-Guerreiro test (complement fixation)
  • Serological tests
  • Xenodiagnosis using reduviid bug
  • ELISA
  • Lymph node biopsy (Vero cell culture of amastigotes, viewed under scanning electron microscope)
• Epidemiology of Chagas disease


  Prevalent in southern US, Mexico, Central and South America, Argentina; animal reservoirs include rodents, opossums, armadillos, dogs, cats
• Treatments for Chagas disease

  • Nitrofurfurylidine drugs
  • Nifurtimox (inhibits intracellular development)
  • Benzinidazole (inhibits nucleic acid)
  • Verapamil (reverses resistance to nifurtimox)
  • Allopurinol
• Prevention methods for Chagas disease

  • Control of insect vector
  • Educational awareness
  • Periodic spraying programs
• Clinically significant Trypanosoma brucei species


  • Trypanosoma brucei gambiense (West African sleeping sickness)
  • Trypanosoma brucei rhodesiense (East African sleeping sickness)
  • Trypanosoma brucei brucei (Nagana disease)
• Vectors for Trypanosoma brucei

  • Glossina palpalis and tachinoides (for T. brucei gambiense)
  • Glossina pallidipes and morsitans (for T. brucei rhodesiense)
• Life cycle of Trypanosoma brucei

  1. Tsetse fly feeds on human host, injecting metacyclic trypomastigotes

  2. Metacyclic trypomastigotes transform into bloodstream trypomastigotes

  3. Bloodstream trypomastigotes multiply in body fluids

  4. Tsetse fly ingests bloodstream trypomastigotes

  5. Trypomastigotes transform into procyclic trypomastigotes in fly's midgut

  6. Procyclic trypomastigotes transform into epimastigotes

  7. Epimastigotes migrate to fly's salivary gland and transform into metacyclic trypomastigotes

  8. Cycle repeats
• Latest studies show Trypanosoma brucei can also have amastigote stage in human host, particularly in the choroid plexus of the brain
• Trypanosomal chancre


  Skin lesion caused by Trypanosoma brucei gambiense
• Winterbottom's sign


  Enlargement of the back of the neck, associated with Trypanosoma brucei gambiense infection
• Kerandel's sign


  Delayed pain response, associated with Trypanosoma brucei gambiense infection
• Neurological symptoms of Trypanosoma brucei gambiense

  Slurred speech, paresthesia, coma
• Hematological changes in Trypanosoma brucei gambiense

  Anemia, thrombocytopenia, disseminated intravascular coagulation
• Trypanosome life cycle in tsetse fly

  1. Tsetse fly feeds on patient

  2. Tsetse fly ingests circulating trypomastigotes

  3. Metacyclic trypomastigotes transform into procyclic trypomastigotes

  4. Procyclic trypomastigotes leave midgut and transform into epimastigotes

  5. Epimastigotes proceed to salivary gland and become metacyclic trypomastigotes

  6. Cycle repeats
• Latest studies/evidence shows that amastigotes can also be present in human hosts, particularly in the choroid plexus of the brain which produces headaches