KINETOPLASIDS

• Flagellates


  Organisms with one or more flagella
• Kinetoplastids


  A group of flagellates that have a disc-shaped DNA-containing structure (kinetoplast) near the base of the flagellum
• Kinetoplastids were formerly part of the Phylum Sarcomastigophora
• Groups of flagellates that infect vertebrates


  • Kinetoplastids
  • Metamonads
  • Dinozoans

  
• Kinetoplastids


  • Have a single mitochondrion
  • Have a disc-shaped DNA-containing structure (kinetoplast) near the base of the flagellum
• Families of Kinetoplastids


  • Trypanosomatidae (uniflagellates)
  • Bodonidae (biflagellates)
  • Cryptobiidae (biflagellates)

  
• Parasitic kinetoplastids infecting vertebrates


  Blood and tissue flagellates
• Parasitic kinetoplastid genera


  • Trypanosoma
  • Leishmania

  
• Other kinetoplastid genera are parasitic in arthropods and should be differentiated from the stages of vertebrate trypanosomatids that utilize arthropods as vectors

  
• Trypanosome


  A general designation for all members of the Trypanosomatidae family, a life cycle stage or morph of members of the family, or a species of the genus Trypanosoma

  
• Main morphs, stages or forms of trypanosomatids


  • Amastigote
  • Bloodstream trypomastigote
  • Epimastigote
  • Metacyclic trypomastigote
  • Promastigote
  • Procyclic trypomastigote
• Trypanosomosis


  One of the world's most important diseases of livestock and humans
• In Africa, vast lands are inhospitable to livestock production because of trypanosomosis
• African sleeping sickness (Human African Trypanosomosis) and Chagas' disease are important scourges of people in Africa and tropical America
• Trypanosomosis is difficult to control due to the heteroxenous life cycle and vaccine development is hampered by antigenic variation
• Variable surface glycoproteins (VSG)


  The surface coat (glycocalyx) of a trypanosomatid is governed by 10 million copies of a single molecular species of antigen that frequently switch
• Sections of the genus Trypanosoma


  • Stercoraria
  • Salivaria
• Stercoraria


  Development occurs in the posterior station (posterior part of the alimentary tract) of the invertebrate host, transmission is by contamination of bite wounds
• Salivaria


  Development occurs in the anterior station of the invertebrate host, transmission is by inoculation (bite of vector)

  
• Trypanosoma species in the Stercoraria section


  • T. theileri
  • T. melophagium
  • T. lewisi
  • T. duttoni
  • T. nabiasi
  • T. cruzi
  • T. rangeli
  • T. avium

  
• Trypanosoma theileri


  Relatively large trypanosome (60-70 μm, up to 120 μm) that is ordinarily nonpathogenic but may cause serious disease and death under stressful conditions, diagnosed by cultivation in NNN medium

  
• Trypanosoma cruzi


  Causes American human trypanosomosis, Chagas' disease, man is the most important host but many domestic and wild animals serve as reservoirs
• Pathogenesis of Trypanosoma cruzi


  1. Metacyclic trypomastigotes actively penetrate mucus membranes and skin

  2. Multiply as amastigotes at the local site resulting in inflammation, encapsulation, and blockade of lymphatics

  3. Invade reticuloendothelial cells of heart, striated muscles, brain, and other tissues, rupture of cells in these organs results in clinical signs
• Diagnostic methods for Trypanosoma cruzi


  • Thick blood smear (acute stage)
  • Xenodiagnosis
  • Cultivation in NNN medium and tissue culture
  • Serological tests (ELISA, CFT, IHA, IIF, DAT)
  • DNA-based methods (hybridization, PCR)

  
• Benznidazole and nifurtimox


  Drugs used to treat Chagas' disease, but have side effects
• Vector control for Chagas' disease


  Insecticide application, treatment of vector habitats with the fungus Beauveria bassiana
• Salivarian trypanosome groups


  • Cyclically transmitted species (invertebrate host = Glossina spp.)
  • Zoonotic trypanosome (T. rhodesiense)
  • Anthroponotic trypanosome (T. gambiense)
  • Pathogenic trypanosomes of domestic animals (T. vivax, T. brucei, T. congolense, T. simiae, T. suis)
• Trypanosoma rhodesiense


  Causes acute Human African Trypanosomosis (HAT) or Rhodesian sleeping sickness, reservoirs include cattle, antelopes, hyenas, lions, and possibly sheep

  
• Trypanosoma gambiense


  Causes chronic HAT known as Gambian sleeping sickness, transmitted by Glossina palpalis and G. tachinoides
• Trypanosoma rhodesiense


  Transmitted by Glossina morsitans, G. swynnertoni, and G. pallidipes

  
• Pathogenic trypanosomes of domestic animals


  • T. vivax (causes 'souma')
  • T. brucei (causes 'nagana')
  • T. congolense (causes 'nagana', 'paranagana', or Gambia fever)
  • T. simiae (infects swine, monkeys, and cattle)
  • T. suis (infects pigs)
• Life cycle of cyclically transmitted salivarian trypanosomes


  1. Extrinsic incubation period in invertebrate host is 15-35 days

  2. Duration of infectivity in invertebrate host is 75-96 days

  
• Pathogenesis of trypanosomosis in domestic animals


  Signs and effects are more or less similar, order of susceptibility is equids > sheep > goats > camels > dogs, with cattle being highly susceptible to T. congolense
• Clinical signs of trypanosomosis in domestic animals


  • Intermittent fever
  • Edematous swellings
  • Watery oculo-nasal discharge
  • Anemia
  • Emaciation despite good appetite
  • Muscular atrophy
  • Incoordination
  • Lumbar paralysis
  • Splenomegaly
  • Hemorrhages
  • Infarcts in various organs
• Trypanosoma evansi


  The first trypanosome shown to be pathogenic for mammals
• DVPS CVM UPLB
• Life cycle in the IH


  15 to 35 d (extrinsic incubation period, EIP)
• T. gambiense


  In Glossina palpalis
• T. gambiense


  • EIP = 34 d
  • Duration of infectivity: 75 d
• T. brucei


  • EIP = 28 d
  • Duration of infectivity: 96 d