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Y3 Parasitology S2 > Protozoa including Giardia > Flashcards

Protozoa including Giardia Flashcards

1
Q

Name some examples of protozoan infections

A
  • Toxoplasma gondii (cats)
  • Neospora caninum (dogs)
  • Sarcocystis (cats and dogs)
  • Cystoisospora (cats and dogs)
  • Giardia
  • Leishmania infantum
  • Babesia canis
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2
Q

Describe the main features of phylum apicomplexa

A
  • Large group of protozoa
  • Mostly intracellular
  • Locomotion by gliding
  • Undergo sexual and asexual reproduction
  • Involved in host cell invasion
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3
Q

How is Toxoplasma gondii linked to sheep?

A

Second most important cause of abortion in sheep in Britain

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4
Q

What spp is the definitive host of Toxoplasma gondii?

A

Cats

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5
Q

What are the 3 life cycle stages of the Toxoplasma gondii parasite?

A
  • Tachyzoite
  • Bradyzoite
  • Oocyst
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6
Q

Describe a tachyzoite

A
  • Intracellular
  • Rapidly dividing
  • Crescent shaped - 2x6um
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7
Q

Describe a bradyzoite

A
  • Within a bradyzoite cyst
  • Neural or muscle tissue
  • Slow growing
  • Persistent
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8
Q

Describe an oocyst

A
  • Unsporulated oocyst passed in faeces
  • Sporulated oocyst contains two sporocysts and four sporozoites
  • 12um
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9
Q

Describe the life cycle of Toxoplasma gondii within the definitive host

A
  • Sexual reproduction part of the life cycle
  • Ingestion of prey containing bradyzoite cysts
  • Cyst wall is digested in the GIT, liberating bradyzoites
  • Bradyzoites invade the intestinal epithelial cells
  • Bradyzoites divide by schizogony giving rise to merozoites
  • Differentiate into male and female gametocytes - microgametes and macrogametes.
  • Fertilization gives rise to an unsporulated oocyst shed with cat faeces
  • Sporulation occurs and generates two sporocysts with four sporozoites each.
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10
Q

What is schizogony?

A

Asexual reproduction

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11
Q

Describe the life cycle of Toxoplasma gondii inside the intermediate host

A
  • Following ingestion sporozoites are released and they cross the gut wall
  • Develop into tachyzoites which replicate rapidly
  • They then differentiate into bradyzoites which form cysts
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12
Q

Describe toxoplasma gondii disease in cats

A
  • No disease
  • No clinical signs
  • Restricted to the sexual cycle in the gut
  • Produce oocysts
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13
Q

Can Toxoplasma gondii be controlled in cats?

A
  • Drugs are not a realistic, practical option

- No vaccines

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14
Q

How is Toxoplasmosis transmitted to humans?

A
  • Tissue cysts in undercooked meat

- Ingesting oocysts contaminating food

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15
Q

Describe vertical transmission of Toxoplasma in humans

A
  • Infected mother prior to pregnancy, foetus is protected by mothers immunity
  • Primary infection during pregnancy can have severe effects on the foetus
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16
Q

What are the effects of Toxoplasma on a foetus?

A
  • Miscarriage, still born
  • Hydrocephalus
  • Convulsions
  • Intracerebral calcification
  • Retinochoroiditis
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17
Q

Which people are most at risk of Toxoplasma?

A

Immunocompromised

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18
Q

How can toxoplasma be controlled in humans?

A
  • Chemotherapy: pyrimethamine and sulphonamides used to treat acute infections in humans
  • Reduce risk of infection, especially pregnant women: oocysts in soil (gardening, unwashed vegetables), cook meat to kill bradyzoite cysts
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19
Q

Which spp are the definitive and intermediate hosts of Neospora caninum

A 
Definitive = dog
Intermediate = dog and cattle
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20
Q

How does the seroprevalence of Toxoplasma compare to Neospora

A

Lower number of Neospora oocysts produced by an infected dog compared to Toxoplasma oocysts produced by an infected cat

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21
Q

Describe the life cycle of Neospora caninum in the definitive host

A
  • Ingestion of bradyzoites from bovine tissues, released into the dogs duodenum where they undergo merogony
  • Transient appearance of oocysts in faeces – sexual phase
  • No disease
  • Antibody response may or may not be present
22
Q

Describe the life cycle of Neospora caninum in the intermediate host

A
  • Transplacental transmission following ingestion
  • Cysts in the muscle of intermediate host
  • No oocysts in faeces as this is the asexual phase
  • Positive antibody response
23
Q

Describe the disease of Neospora caninum in dogs vs cattle

A
  • Disease in dogs – neonatal paresis

* Disease in cattle – abortion

24
Q

What are the clinical signs of Neospora caninum in young dogs?

A
  • Ataxia, hindlimb paresis, loss of reflexes
  • Ascending paralysis, dysphagia
  • Hyperextension of hindlimb(s)
25
Q

What are the clinical signs of Neospora caninum in older dogs?

A
  • CNS disturbances
  • Abnormal behaviour
  • Vision defects, seizures
  • Myocarditis, dermatitis
  • Pancreatitis
26
Q

How can Neospora caninum be diagnosed?

A
  • Clinical signs
  • Serology by IFAT
  • Creatine kinase elevation
  • Muscle biopsy and tissue aspirates - PCR or immunocytochemistry to identify the parasites
27
Q

How can Neospora caninum be treated?

A
  • Clindamycin (same as Toxoplasma)
  • Initiate treatment as soon as possible after clinical signs develop
  • Prognosis variable as it doesn’t act on the bradyzoite cysts
  • Doesn’t stop vertical transmission so don’t breed from an Ab + mother
28
Q

What are the main features of the life cycle of Sarcocystis spp?

A

Two host life cycle – prey-predator:

  • Prey: asexual reproduction & muscle cyst development (sacrocyst)
  • Final predator host: intestinal sexual reproduction & production of mature oocysts
29
Q

What are the two predator-prey relationships for Sarcocystis spp?

A

Sheep - Dog

Cattle - cat

30
Q

Describe the sporulated oocyst of Sarcocystis spp

A
  • In faeces of dog/cat (two sporocysts each containing four sporozoites) – ready to infect
  • Classical 2 sporocyst appearance with a very light surrounding membrane encasing them which disintegrates easily
31
Q

Cattle infected with Sarcocystis at which point in pregnancy may abort?

A

Third trimester

32
Q

What are the main features of the Cystiospora spp life cycle?

A
  • Direct life cycle – no asexual part of the cycle
  • Infection by faeco-oral transmission
  • Oocysts passed in faeces (20-40µm)
  • Sporulated oocysts - 2 sporocysts, 4 sporozoites
33
Q

What is the clinical signs of Cystiospora spp infection?

A

Diarrhoea in puppies and kittens

34
Q

How is Cystiospora spp diagnosed?

A
  • History and clinical signs
  • Oocysts sometimes differentiated on size
  • The more oocysts there are, the more likely disease is as a result of coccidia
35
Q

How is Cystiospora spp controlled?

A

Good sanitation and treat with sulphonamides

36
Q

Which protozoa is the cause of travellers diarrhoea in humans?

A

Giardia

37
Q

How does Giardia affect puppies?

A

Important cause of Diarrhoea

38
Q

What are the two morphological stages of Giardia?

A

Trophozoite

Cyst

39
Q

Describe the trophozoite stage of Giardia and its appearance

A
  • Diving stage
  • Adhesive disc attaches it to the intestinal mucosa
  • Pear shaped (12-15um x 5-9um)
  • Bi-nucleated
  • 4 pairs of flagellae (8 total)
40
Q

Describe the cyst stage of Giardia and its appearance

A
  • Found in the intestinal lumen and faeces
  • Transmitted among hosts
  • Oval/ellipsoid, smooth cyst wall
  • 8x12um
  • Each cyst contains two trophozoites with 4 nuclei total
41
Q

Describe the life cycle of Giardia

A
  • Infective cysts from the environment are ingested by host
  • Excyst in small intestine: each cyst releases 2 actively moving trophozoites
  • Trophozoites attach to the intestinal epithelium and multiply asexually by longitudinal binary fission
  • Secrete cyst forming protein and transform into multi-nucleated resistant cysts excreted in the faeces
42
Q

How long is the PPP of Giardia?

A

1-2 weeks

43
Q

What are the clinical signs of Giardia?

A
  • Puppies
  • Trophozoites erode mucosa and villi
  • Malabsorptive diarrhoea
  • Dehydration
  • Steatorrhoea (greasy stools)
44
Q

How is Giardia controlled and treated?

A
  • Control based on good hygiene
  • Clean drinking water
  • Treatment with metronidazole
  • Fenbendazole licensed for use in puppies
  • Zoonotic: important to warn owners
45
Q

Tritrichomonas foetus is an obligate parasite of which two spp?

A
  • Bovine reproductive tract

- Feline gastrointestinal tract

46
Q

Tritrichomonas foetus is a commensal parasite of which spp?

A

Pigs - nasal cavities, intestines, and stomachs

47
Q

How does Tritrichomonas disease affect cattle?

A

Cause of abortion and infertility in cows

48
Q

How does Tritrichomonas disease affect cats?

A

Diarrhoea, colitis (large bowel)

Young cats

49
Q

How is Tritrichomonas diagnosed in cats and differentiated from Giardia?

A
  • Faecal smears: differentiate from Giardia
  • Culture from faecal sample (In Pouch system)
  • Giardia = slow moving
  • Tritrichomonas = jerky, rapid movements
50
Q

How is Tritrichomonas foetus treated?

A

Treatment with ronidazole (related to metronidazole) – not licensed in the UK

51
Q

Diarrhoea is a typical clinical sign for which 4 protozoan infections?

A
  • Sarcocystis spp.
  • Cystoisospora (Isospora)
  • Giardia spp.
  • Tritrichomonas foetus

Y3 Parasitology S2 (13 decks)

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