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PROTOZOA
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Toxoplasma gondii - Ke Hu and John Murray

Protozoa

Question Answer Article
What are the four different ways protozoa can move?
  • Cilia
  • Flagellum
  • Pseduopodia
  • Gliding
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How do protozoa reproduce?
  • By binary fission
  • By schizogony
  • By sporogony
  • By gametogeny
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Briefly summarise the life cycle of protozoa
  • The infectious sporozoite are released from the oocyst invading epithelial tissue
  • The nucleus of the sporozoites divides forming a schizont which contains merozoites (schizogony)
  • Schizont ruptures releasing merozoites which form micro and macrogamonts in the epithelial tissue (gametogeny)
  • Microgamonts penetrate the macrogamont forming the zygote
  • The zygote forms the oocyst which is passed in the faeces
  • Sporulation occurs which makes the oocyst infectious
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Coccidia

Question Answer Article
What is the transmission and life cycle of Eimeria species?
  • Direct transmission
  • Faecal-oral route
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What is the transmission and life cycle of Isospora species?
  • Usually direct transmission by the faecal-oral route
  • Some species use facultative intermediate hosts forming tissue cysts
    • Transmission is then by the faecal-oral or route or via ingestion of the intermediate host
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Cryptosporidia

Question Answer Article
What is the main species of Cryptosporidium which infects humans and domestic animals?
  • C. parvum
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True or False: In Cryptosporidium infections unsporulated oocysts are passed in the faeces
  • False
  • Sporulated oocysts are passed in the faeces
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How are Cryptosporidium infections passed between hosts?
  • Direct faecal-oral transmission
  • Water-bourne infections
  • Autoinfection can also occur
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How are Cryptosporidium infections prevented?
  • Isolate and quarantine brought in calves
  • Good hygiene and adequate disinfection of calf pens
  • Goog hygiene of humans working and visiting farms
  • Halofuginone and other drug treatments
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Giardia

Question Answer Article
What is the key points of the life cycle and prepatent period of Giardia?
  • Simple life cycle
  • Direct life cycle
  • Reproduce by binary fission
  • 5-6 day prepatent period
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How do both people and animals become infected by Giardia?
  • Water bourne transmission
  • Direct faecal-oral transmission
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How would you diagnose a Giardia infection?
  • The cysts are heavy and do not float well in saturated sodium chloride solution
  • Cysts excretion is intermittent so faeces need to be collected and sampled over 3 days
  • Cyst antigen can be detected in faeces by an immunoassay
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Piroplasmida

Tissue Cyst Forming Coccidia

Tropical Protozoa

Other Important Protozoa