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MODULE 4 - Infectious Agents > PARASITOLOGY - Protozoa > Flashcards

PARASITOLOGY - Protozoa Flashcards

1
Q

Which protozoan parasites are an important cause of abortion and perinatal mortality in ovine species?

A

Toxoplasma Gondii

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2
Q

Toxoplasma is in which subcategory of protozoa?

A

Coccidia

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3
Q

What is the final host for Toxoplasma Gondii?

A

Felids (domestic cats)

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4
Q

What are the intermediate hosts for Toxoplasma Gondii?

A

All mammals/birds

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5
Q

Describe the lifecycle of T. gondii

A
  1. Felids are infected by the ingestion of tissue containing bradyzoite tissue cysts –>
  2. Bradyzoites invade gut epithelial cells and undergo Schizogony (rounds of asexual reproduction) –>
  3. Sexual phase of the lifecycle occurs in the gut epithelial cells, producing zygotes which form walled oocysts –>
  4. Unsporulated oocysts are shed in the felid faeces –>
  5. Oocysts become infective through sporulation –>
  6. Sporulated oocysts are ingested by the intermediate host and the sporozoites are released, invading the gut epithelial cells and forming tachyzoites –>
  7. Tachyzoites undergo rapid asexual reproduction and are released from the gut epithelial cells and distribute throughout the body –>
  8. The immune response will eventually control the tachyzoites however the tachyzoites evade the immune response through transforming into bradyzoite tissue cysts located in the muscle, neural and organ tissue –>
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6
Q

What are the ideal conditions required for oocyst sporulation?

A
  • Moisture
  • 25 degrees celsius
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7
Q

Which part of the T. gondii lifecycle contributes to the direct pathology of Toxoplasmosis?

A

Uncontrolled multiplication of tachyzoites resulting in inflammation and tissue necrosis

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8
Q

(T/F) Toxoplasma gondii is only infective if infecting the host for the first time

A

TRUE

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9
Q

How does T. gondii alter the behaviour of rats (intermediate host) and why?

A

T. gondii makes rats less neophobic and also attracted to cat urine to increase transmission probability to their final host (the cat)

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10
Q

How is T. gondii transmitted to the foetus of pregnant ewes?

A

Tachyzoites undergo trans-placental transmission and infect the foetus

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11
Q

During which phase of the gestation period is T. gondii most likely to cause abortion in ewes?

A

During the first trimester (within the first 50-55 days or gestation)

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12
Q

Describe what is most likely to happen to ovine foetuses infected with T. gondii during the second trimester?

A
  • Premature stillbirth/weak lamb
  • Chocolate brown mummified foetus
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13
Q

Describe the appearance of placental lesions that can be seen in an animal that has T. gondii

A
  • Bright to dark red cotyledons
  • Small white necrotic foci in the cotyledons of the placenta
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14
Q

List the diagnostic tests that can be used to identify T. gondii in sheep

A
  • Antibody tests on foetal fluids and/or precolostral lamb serum
  • Immunohistochemistry
  • PCR test on the placental tissue
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15
Q

Which tests can be used to confirm that an animal is suffering from a first infection of T. gondii?

A
  • Antibody tests with IgM detection
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16
Q

Why is T. gondii such a significant public health concern?

A

Because T. gondii is zoonotic and can be fatal to immuno-deficient patients and can be transferred from mother to foetus in first time infected pregnant women, causing congenital toxoplasmosis

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17
Q

How is T. gondii zoonotically transmitted?

A
  • Oocyst ingestion
  • Ingestion of infected undercooked meat with bradyzoite tissue cysts
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18
Q

How can T. gondii affect human foetuses if infected within the first trimester?

A
  • Miscarriage/stillbirth
  • Brain lesions and Hydrocephalus if the foetus does survive
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19
Q

How can T. gondii affect human foetuses if infected within the second trimester?

A
  • Learning difficulties
  • Chorioretinitis
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20
Q

How can T. gondii affect human foetuses if infected within the third trimester?

A
  • Can be born clinically normal but develop lesions years later
  • Learning difficulties
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21
Q

Which protozoan parasite is an important cause of abortion and perinatal mortality in bovine species?

A

Neospora Caninum

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22
Q

Neospora is in which subcategory of protozoa?

A

Coccidia

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23
Q

What is the final host of N. caninum?

A

Canines

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24
Q

What are the intermediate hosts of N. caninum?

A

A large range of mammals

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25
Q

Describe the lifecycle of N. caninum

A
  1. HORIZONTAL TRANSMISSION: Canines are infected through ingestion of tissue with bradyzoite tissue cysts –>
  2. Sexual phase of the lifecycle occurs within the gut epithelial cells producing zygotes which form walled oocysts
  3. Unsporulated oocysts are shed in the canine faeces –>
  4. Oocysts become infective through sporulation –>
  5. Sporulated oocysts are ingested by the intermediate host and the sporozoites are released, invading the gut epithelial cells and forming tachyzoites –>
  6. Tachyzoites undergo rapid asexual reproduction and are released from the gut epithelial cells and distribute throughout the body
  7. The immune response will eventually control the tachyzoites however the tachyzoites evade the immune response through transforming into bradyzoite tissue cysts located mainly in the neural tissue –>
  8. VERTICAL TRANSMISSION: a female mammal may be infected persistently with bradyzoite tissue cysts and when she becomes pregnant the immune response controlling the parasite wanes and the bradyzoite tissue cysts rupture, releasing the bradyzoites which transfer into tachyzoites –>
  9. The tachyzoites multiply rapidly and distribute throughout the body and across the placenta, infecting the developing foetus
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26
Q

How can N. caninum infection be maintained within the herd via vertical transmission from dam to calf?

A

The dam may be persistently infected with bradyzoite tissue cysts, when she becomes pregnant the immune response that controls the parasite wanes and the cysts rupture releasing bradyzoites. These convert back into tachyzoites which rapidly multiply and spread throughout the dam. The tachyzoites then cross the placenta to infect the developing foetus. If this happens during the 3rd trimester the calf will be persistently infected and can then pass the infection to the next generation of calves when they become pregnant.

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27
Q

How does N. caninum affect bovine foetuses infected within the first trimester?

A

Abortion

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28
Q

How does N. caninum affect bovine foetuses infected within the second trimester?

A

Neurological signs

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29
Q

How does N. caninum affect bovine foetuses if infected within the third trimester?

A

Clinically normal but can pass on the infection in future pregnancies via trans-placental vertical transmission

30
Q

List the diagnostic tests that can be used to identify N. caninum in bovine species

A
  • ELISA test used to detect antibodies in herd serum
  • ELISA test to detect antibodies in foetal fluid
  • Examination of the neural tissue in the aborted foetus for lesions (non suppurative encephalitis)
  • Immunohistochemistry
  • PCR detection of the parasite
31
Q

What is non suppurative encephalitis?

A

Inflammation of the brain observed in postmortem histopathological examinations and is indicative of an infectious aetiology

32
Q

What are the economic losses caused by N. caninum in cattle?

A

Economic losses due to abortion, low milk yield, culling/replacement

33
Q

Are there any licensed/effective drugs or vaccines against N. caninum?

A

NO

34
Q

Why is the control of the N. caninum protozoa so challenging?

A

N. caninum is so challenging to control as is remains within herd animals due to trans-placental vertical transmission

35
Q

Is N. caninum zoonotic?

A

NO

36
Q

Eimeria, Isospora and Cryptosporidium are in which subcategory of protozoa?

A

Coccidia

37
Q

(T/F) Coccidia protozoa are host-specific parasites

A

TRUE

38
Q

(T/F) The severity of host pathology when infected with a coccidia protozoa is dependent of the infectious dose

A

TRUE

39
Q

How are Eimeria protozoa transmitted?

A

Via the faecal/oral route

40
Q

Describe the lifecycle of Eimeria

A
  1. Host ingests sporulated oocysts –>
  2. Sporozoites are released from the oocysts and infect gut epithelial cells where they become trophozoites –>
  3. Trophozoites undergo rapid asexual reproduction and form schizonts containing merozoites (a process known as Schizogony) –>
  4. The schizonts rupture, destroying the gut epithelial cells and releasing the merozoites which infect more gut epithelial cells –>
  5. Merozoites undergo Gametogony (sexual reproduction) where the merozoites mature into male micro-gametocyte and female macro-gametocyte. The male micro-gametocyte ruptures releasing microgametes which fertilise the macro-gametocyte forming a zygote –>
  6. The zygotę matures into an unsporulated walled oocyst which its shed in the host species –>
  7. In the right conditions, the oocyst will be sporulated –>
41
Q

How many sporocysts and sporozoites are contained within an Eimeria sporulated oocyst?

A

Eimeria sporulated oocysts contain four sporocysts containing two sporozoites within each sporulated oocyst

42
Q

List the seven pathogenic strains of Eimeria that infect chickens

A

E. tenella
E. brunetti
E. necatrix
E. maxima
E. mitis
E. acervulina
E. praecox

43
Q

Describe the pathogenesis of Eimeria in all animals

A

Epithelial cell destruction and villous atrophy (diarrhoea and malabsorption) caused by the shizont rupture within the gut epithelial cells

44
Q

What are the clinical signs of Eimeria parasites in chickens?

A
  • Flock huddled together
  • Dirty and ruffled feathers
  • Drooped wings
  • Ball-like posture
  • Blood and mucous in the faeces
  • Diarrhoea
45
Q

What would indicate Eimeria in a post mortem examination?

A
  • Anaemic internal organs
  • Identification of schizonts on tissue slides
46
Q

What are the husbandry conditions that can prevent Eimeria transmission in chickens?

A
  • Hygiene and biosecurity
  • Use of prophylactic anticoccidial drugs
47
Q

What are the three pathogenic strains of Eimeria that infect cattle?

A

E. bovis
E. zuernii
E. auburnensis

48
Q

What are the clinical signs of Eimeria in cattle?

A
  • Diarrhoea (blood is rare)
  • Tenesmus
  • Anorexia
  • Slight pyrexia
49
Q

When are cattle most predisposed to coccidiosis?

A
  • Between 1 month - 1 year
  • Stressed adults
50
Q

(T/F) Bovine coccidiosis has a high morbidity but low mortality

A

TRUE. However extremely high levels of infection can cause neurological signs which is often a sign of fatality

51
Q

What are the two pathogenic strains of Eimeria in sheep?

A

E. ovinoidalis
E. crandallis

52
Q

What are the clinical signs of coccidiosis in sheep?

A
  • Diarrhoea (sometimes there can be blood/mucous)
  • Weight loss
  • Anorexia
  • Dehydration
  • Anaemia
  • Pyrexia
53
Q

Why are twins or triplets more susceptible to ovine coccidiosis?

A

Due to the distribution of colostrum causing a reduction in passive immunity

54
Q

What are the two pathogenic strains of Eimeria in rabbits?

A

E. flavescens
E. intestinalis

55
Q

What are the clinical signs of coccidiosis in rabbits?

A
  • Anorexia
  • Diarrhoea (sometimes there can be blood/mucous)
  • Emaciation
56
Q

What are the two pathogenic strains of Isospora seen in cats?

A

I. felis
I. revolta

57
Q

What are the two pathogenic strains of Isospora seen in dogs?

A

I. canis
I. ohioenesis

58
Q

What is the pathogenic strain of Isospora seen in pigs?

A

I. suis

59
Q

How many sporocysts and sporozoites are contained within an Isospora sporulated oocyst?

A

Isospora sporulated oocysts contain two sporocysts containing four sporozoites within each sporulated oocyst

60
Q

How do rodents act as paratenic hosts for Isospora?

A

Rodents can act as paratenic hosts via the ingestion of sporulated oocysts and forming hypnozoites in their tissues which can be ingested by the final host

61
Q

What are the clinical signs of Isospora in cats and dogs?

A
  • Diarrhoea (sometimes there can be blood/mucous)
  • Weight loss
  • Anorexia
  • Dehydration
  • Vomiting
62
Q

Which drugs can be used to treat Isospora/coccidiosis in cats and dogs?

A
  • Sulphomides
  • Amprolium
63
Q

What is the other name commonly used to describe Isospora suis?

A

‘10 day scour’

64
Q

What are the clinical signs of I. suis?

A
  • Diarrhoea
  • Yellowish/grey faeces
  • Dehydration
  • Weight loss
65
Q

(T/F) Coccidiosis is not generally associated with poor husbandry and overcrowding

A

FALSE. Coccidiosis is spread via the faecal/oral route so a clean, biosecure area is required. Sufficient nutrients and good health also helps to boost the immune system, helping animals build immunity to the parasites

66
Q

What is the most clinically significant pathogenic strain of Cryptosporidium?

A

C. parvum

67
Q

Why is C. parvum so clinically significant in veterinary and human medicine?

A

C. parvum is zoonotic

68
Q

How is C. parvum transmitted?

A

Via the faecal/oral route

69
Q

Describe the pathogenesis of C. parvum

A

Epithelial cell destruction and villous atrophy (diarrhoea and malabsorption)

70
Q

Describe the lifecycle of Cryptosporidium

A
  1. Host ingests oocysts –>
  2. Sporozoites are released from the oocysts and infect gut epithelial cells where they become trophozoites –>
  3. Trophozoites undergo rapid asexual reproduction and form schizonts containing merozoites (a process known as Schizogony) –>
  4. The schizonts rupture, destroying the gut epithelial cells and releasing the merozoites which infect more gut epithelial cells –>
  5. Merozoites undergo Gametogony (sexual reproduction) where the merozoites mature into male micro-gametocyte and female macro-gametocyte. The male micro-gametocyte ruptures releasing microgametes which fertilise the macro-gametocyte forming a zygote –>
  6. The zygotę matures into a thin walled sporulated oocyst which ruptures leading to self infection
  7. The zygotę matures into a thick walled sporulated oocyst which is shed in the faeces

Cryptosporidium oocysts DO NOT contain sporocysts

71
Q

What are the clinical signs of C. parvum infection?

A
  • Diarrhoea (sometimes blood/mucous)
  • Weight loss
  • Anorexia
72
Q

What is the specialist stain required to identify Cryptosporidium for parasitological diagnosis?

A

Ziehl Neelsen stain

MODULE 4 - Infectious Agents (20 decks)

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