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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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How long is the prepatent period of poultry Eimeria species?
  • 1 week
  • Sporulation takes 2-3 days
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Name the malabsorptive Eimeria species
  • E. maxima
  • E. acervulina
  • E. mitis
  • E. praecox
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Name the haemorrhagic Eimeria species
  • E. necatrix
  • E. brunetti
  • E. tenella
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Which area of the gastrointestinal tract does E. acervulina, E. maxima, E. tenella and E. necatrix affect and what kind of lesions are produced?
  • E. acervulina affects the proximal gut forming white ladder lesions
  • E. maxima affects the mid-gut producing a pink exudate
  • E. tenella affects the ceaca forming a core of dark, haemorrhagic blood
  • E. necatrix affects the mid-gut forming salt and pepper leions
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What are the two main Eimeria species which affect cattle and what is the prepatent period?
  • E. zuernii
  • E. bovis
  • 2-3 week prepatent period
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What are the two significant Eimeria species which affect sheep and what is the prepatent period?
  • E. ovinoidalis
  • E. crandalis
  • 2 week prepatent period
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What is the most significant species of Isospora which affects pigs and what the prepatent period?
  • I. suis
  • 1 week prepatent period
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Which parts of the gastrointestinal tract do the Eimeria species which affects rabbits inhabit?
  • 2 inhabit the caecum
  • 1 inhabits the bile duct epithelium (E. steidae)
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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

Question Answer Article
True or False: Both trans-stadial and trans-ovarian transmission can occur in Babesia species
  • True
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What are the recognisable features of small Babesia species and give an example
  • Peripheral nucleus
  • Obtuse angle
  • B. divergens
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What are the recognisable features of large Babesia species and give an example
  • Central nucleus
  • Acute angle
  • B. major
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What are the predisposing features to Babesia infection?
  • Susceptible animals introduced into an infected area
  • Infected ticks introduced into a clean area
  • Infected cattle introduced into an area with clean ticks
  • Temporary reduction in the tick population decreasing the transmission rate (causing enzootic instability)
  • Infected are transported or stressed in other ways, e.g. parturition
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What are the different vectors for Babesia species?
  • Ixodes ricinus for B. divergens
  • Haemaphysalis for B. major
  • Boophilus for B. bovis and B. bigemina
  • Dermacentor and Rhipicephalus for B. canis
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What species are the natural vectors for Cytauxzoon?
  • Ticks
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Where do schizonts of Cytauxzoon felis develop?
  • In macrophages
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What is the main condition caused by Theileria parva?
  • East Coast Fever
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What is the main condition caused by Theileria parva and what is the intermediate host?
  • East Coast Fever
  • Rhipicephalus appendiculatus
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What is the pathogenesis of Theileria parva infections?
  • Proliferation in the lymphoblasts
  • Proliferation in the local lymph node followed by spread throughout the body
  • Lymphocyte depletion
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What are the clinical signs of Theileria parva infection?
  • Pyrexia
  • Enlarged local lymph node
  • Loss of condition
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Tissue Cyst Forming Coccidia

Question Answer Article
What are the two main species of Neospora of veterinary interest and which animals do they affect?
  • N. caninum
    • Dogs
  • N. hughesi
    • Horses
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How long is the prepatent period of Neospora?
  • 5 days
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What are the clinical signs of Neospora infections in dogs?
  • Ascending paralysis
  • Sudden collapse due to myocarditis
  • Muscle wasting
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What are the clinical signs of Neospora infections in cattle?
  • Abortion
  • Encephalomyelitis
  • Paresis
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What are the clinical signs of Neospora infections in horses?
  • Myeloencephalitis
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Tropical Protozoa

Other Important Protozoa