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Parasitology > Protozoa - Cyst forming coccidia > Flashcards

Protozoa - Cyst forming coccidia Flashcards

1
Q

Toxoplasma gondii sporulated oocyst configuration

A

1 oocyst: 2 sporocysts: 4 sporozoites

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2
Q

Significance of Toxoplasmosis

A

Economic losses

Zoonosis

Abortions in humans and small ruminants

Systemic disease - involves CNS

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3
Q

Toxoplasma gondii

DH

IH

PPP

How long is patency?

A

DH = felid

IH = any warm blooded animal

PPP = 1 week

Patent for 1 month

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4
Q

Transmission of Toxoplasma gondii

A

Oral -> ingestion of oocysts.

Oocysts resistant in environment for up to 18 months

Ingestion of tissue cysts (raw / undercooked meat / unpasteurised milk)

transplacental and transmammary to foetus

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5
Q

Toxoplasma gondii site sexual replication

A

only in feline intestines

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6
Q

Where can asexual replication of T. gondii occur?

A
  • feline intestinal epithelium
  • In any nucleated cell in IH
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7
Q

What is a tachyzoite?

A

Rapidly dividing (schizogony) parasite that is moving around te body, penetrating tissues and causing damage

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8
Q

What is a bradyzoite?

A

Dormant stage in IH brain, heart or skeletal muscle, long lived cysts. Cysts develop as the host immunity increases.

Can differentiate into a sporozoite -> transmit infection when it is eaten.

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9
Q

T. gondii lifecycle

A

Oocyst excreted from cat -> sporulation ->

ingestion by IH -> schizogony and tachyzoite formation -> bradyzoite formation as host immunity increases -> ingestion by felid.

OR

-> transmammary/tranplacental infection of kittens -> large amounts of oocyst secretion (20 million in 10-21 days) - kitten develops immunity and reinfection is rare

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10
Q

What happens if a previously immune animal with bradyzoites becomes immunocompromised (HIV, FeLV, FIV)?

A

Bradyzoites -> tachyzoites -> disease

Won’t get shedding of oocysts as the tachzoite will not go back into the intestines

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11
Q

Pathogenesis of T. gondii

A
  • acute infection in naive host
  • re activation of latent infection of immunocompromised animal
  • > tachyzoites multiply and destroy tissue. Muscle will regenerate but nerves may not.
  • can cause abortion, stillborn or congenital abnormalities if T. gondii is acquired durring pregnancy
  • if she is infected prior to pregnancy the immunity is passed on to the foetus
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12
Q

Toxoplasmosis in cats

A

Intestinal - self limiting diarrhoea

  • systemic disease
  • pyrexia and multi systemic disease
  • CNS, hepatic necrosis -> jaundice, uvetitis, interstitial pneumonia
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13
Q

Toxoplasmosis in dogs

A
  • neurological
  • gastrointestinal
  • respiratory signs

+- ocular signs

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14
Q

Public health significance

A

majority asymptomatic

  • 1/3 exposed
  • mild flu like symptoms - fever, sore throat, weakness

High infectious dose in outbreak -> chorioretinitis

HIV-AIDS / organ transplant patients -> 10-30% fatality from latent or newly aquired infection. Encephalitis, pneumonia, ocular disease

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15
Q

Pregnant women risks

A
  • Life-long immunity once exposed -> protect against vertical transplacental transmission unless immunocompromised
  • if infection contracted during pregnancy -> may be transmitted to foetus
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16
Q

Diagnosis of T. gondii

A

Detection of T. gondii antibodies - IgM or rising IgG. Acute infection indicated by 4-16 fold increase in antibodies over a 2 week period.

Dection of tachyzoites

  • biopsy, (necropsy placenta, amniotic fluid, foetus), cytology and PCR
  • CBC and biochem with consistant finding of organ specific disease
17
Q

Treatment of T. gondii

A

Chemotherapy as this targets rapridly dividing tachyzoites (can’t get bradyzoites easily).

  • Pyrimethamine +
  • clindamycin, sulphonamides or azithromycin

Clinical improvement usually noticed after 24-48 hours unless permanent organ damage.

18
Q

Control of T. gondii

A
  • Hygiene!
  • prevent ingestion of oocysts; gloves when gardening/ empty kitty litter
  • Thorough cooking or freezing of meat
  • washing potentially contaminated food stuff
  • vaccine (toxovax) for sheep
19
Q

Neopspora caninum

DH

IH

Transmission

Oocyte configuration

A

DH = dog

IH - range of mammals

Transmitted orally/transplacental

Configuration 1:2:4

20
Q

Sites of Neospora caninum

A

Cysts in various tissues; brain, spinal cord and muscles.

21
Q

Lifecycle of Neospora caninum

A
  • Transplacental transmission can occur in dogs but poorly understood.
  • dogs become infected with tissue cysts and subsequently excrete oocysts. Poorly understood
22
Q

Significant of N. caninum

A

Cattle:

  • abortions - 5-7 months
  • congenitally abnormal calves
  • asymptomatic carrier -> persistent infection

Dogs:

  • paralysis in pups
  • multi systemic in older immunocompromised animals
  • NOT ZOONOTIC
23
Q

Neosporosis in dogs

A
  • polyradiculo - neuritis
  • myositis
  • degenerative

weakness in legs -> loss of propriocetion

24
Q

Diagnosis of N. caninum

A

Parasites detected in histological section of necropsy/biopsy material by immunolabelling

25
Q

Treatment of N. caninum

A

Clindamycin, pyrimethamin + sulphonamides

26
Q

Sarcocystis hosts

A

Many host-specific species

  • canids, felids, humans as DH

IH - omnivores and herbivores -> merogony - tissue cysts

27
Q

Sarcocyst lifecycle

A
  • macro and microgamete in DH intestines -> oocyst -> sporocyst in environment -> ingested by IH -> sporozoite -> merozoite -> schizont in capillaries -> zoites and metrocytes in cyst -> ingestion by DH
  • IH -> asexual replication (schizogony) in vasculature cell walls
  • IH-> tissue cysts
  • DH has gametogony and sporogony -> infective sporocytes excreted
28
Q

Significant of Sarcocystis

A
  • condemnation of carcasses (sheep and cattle); small systs often go unoticed by see macroscopic granulomas.
  • Acute infection - merogony -> vasculitis
  • abortions and stillbirths
  • multisystemic disease
  • equine protozoal myeloencephalitis (S. neurona)
29
Q

Sarcocystis zoonotic infection

Human as a DH

and IH for

A

DH for S. hominis (cattle IH) and S. suihominis (pig IH)

IH for S. nesbitti- reptile DH

-> mutisystemic signs - relapsing fever, vasculitis, myositis, myalgia

30
Q

Pathogenicity of Sarcocystis

A
  • DH usually asymptomatic
  • systemic infections in IH
  • Similar to T. gondii but no schizogony in the DH

Tachyzoite - vascular endothelial cells -> acute: petechia, echymosis, anaemia and oedema. Can cause abortions and stilbirth

Bradyzoite - musculature -> chronic: premunition. muscle atrophy, myositis and myocarditis

Smaller = more pathogenic

Larger = more economic loss (found in meat)

31
Q

Diagnosis of Sarcocystis

A
  • Gross post mortem inspection of carcass
  • histo
  • PCR on tissue
  • DH - sporocysts in faeces
  • Serological tests?
32
Q

Control of Sarcocystis

A

Hygiene!

  • don’t feed undercooked/unfrozen meat to carnivores
  • exposure of livestock to sporocyst - contaminated feed
33
Q

Treatment of Sarcocystosis

A
  • coccidiostats - DH
  • partial efficacy in IH
  • not required as light infections are protected against acute disease?

Parasitology (30 decks)

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