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Sheep... > Parasites (Yr 2) > Flashcards

Parasites (Yr 2) Flashcards

1
Q

what nematodes are found in the small intestine of sheep?

A

Cooperia spp.
Trichostrongylus spp.

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2
Q

what nematodes are found in the abomasum of sheep?

A

Teladorsagia circumcincta
Trichostrongylus axei

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3
Q

what is the appearance of adult Telasorsagia circumcincta?

A

1cm slender pink/brown worm with fine cervical papillae
(males have bursa/spicules)

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4
Q

what species have a typical trichostrongyle life cycle?

A

T. circumcinta
Cooperia spp.
Trichostrongylus spp.

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5
Q

what is hypobiosis?

A

arrested development of larvae within the host triggered by a drop in ambient temperature

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6
Q

what is the typical trichostrongyle lifecycle?

A

adults produce barrel shaped eggs that are passed in faeces
L1 develops within the egg then hatches and feeds to moult to L2 and L3 (ensheathed)
L3 is released from faeces by rain and then ingested by host and burrows into the gastric gland to develop to L4 and L5 which emerge and reproduce

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7
Q

what is the pre-patent period?

A

time taken from ingestion of L3 to when eggs are detected in faeces

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8
Q

what is the gastric glands function?

A

maintain pH of abomasum allowing the bacteriostatic effect and conversion of pepsinogen to pepsin

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9
Q

what is the pathogenesis of Teladorsagia circumcincta?

A

L4/L5 damage gastric glands when they emerge, causing them to be replaced by undifferentiated epithelial cells which means loss of acid production and increased abomasal pH
this means loss of bacteriostatic effect, no pepsinogen conversion and increased permeability of mucosa

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10
Q

what animals is type 1 PGE seen in?

A

first season grazing lambs around mid-summer onwards

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11
Q

what are the clinical signs of type 1 PGE?

A

profuse watery diarrhoea, inappetence, dehydration, poor weight gain (loss of plasma proteins and reduced intakes)

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12
Q

what animals is type 2 PGE seen in?

A

yearling animals in late winter to early spring due to simultaneous emergence of hypobiosed larvae

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13
Q

what type of scour does Trichostrongylus spp. cause?

A

black scour

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14
Q

what is the appearance of Trichostrongylus spp.?

A

very small hair like worms (5mm) with excretory notch at head end

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15
Q

does Trichostrogylus spp. hypobiose?

A

yes

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16
Q

what is the pre-patent period for a typical trichostongyle life cycle?

A

3 weeks

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17
Q

what is the pathogenesis of Trichostrongylus spp.?

A

L4/L5 develop deep within mucosa forming sub-epithelial tunnels which leads to villous atrophy, haemorrhage, oedema and diarrhoea

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18
Q

what animals is Trichostrongylus spp. typically seen in?

A

store lambs around autumn

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19
Q

what are the clinical signs of Trichostrongylus spp.?

A

black scour, poor weight gain, poor skeletal growth

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20
Q

what is the appearance of Cooperia spp.?

A

watch spring with cephalic vesicle

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21
Q

what is the pathogenesis of Cooperia spp.?

A

mild pathigenesis - heavy burdens can cause villous atrophy, oedema, and poor weight gain

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22
Q

what worms are found in the abomasum of sheep?

A

Haemonchus contortus
Teladorsagia circumcincta
Trichostrongylus axei

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23
Q

what worms are found in the small intestine?

A

Nematodirus battus
Trichostrongylus spp.
Cooperia spp.

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24
Q

what are the classes of anthelmintics?

A
  1. benzimidazoles
  2. imidathiozoles
  3. macrocyclic lactones
  4. amino acetonitriles
  5. spiroindoles
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25
Q

which benzimidazole also targets liver fluke?

A

triclabendazole

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26
Q

what are some examples of benzimidazoles?

A

fenbendazole, albendazole, flubendazole, triclabendazole

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27
Q

what is the mode of action of benzimidazoles?

A

inhibit microtubule transport to prevent enzyme release

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28
Q

what do benzimidazoles target?

A

primarily nematodes, they are ovoidal and effective at targeting hypobiosed larvae

29
Q

what are the main imidathiazoles?

A

levamisole and pyrantel

30
Q

what is the mode of action of imidathiazoles?

A

causes paralysis to parasites

31
Q

what do imidathiazoles target?

A

primarily nematodes in gut dwelling stage (short acting)

32
Q

what are the two types of macrocyclic lactones, with examples?

A

avermectin (ivermectin, doramectin, selamectin)
milbemycin (moxidectin, milbemycin)

33
Q

what is the mode of action of macrocyclic lactones?

A

paralysis of parasite

34
Q

what do macrocyclic lactones target?

A

only nematodes but can target migrating and hypobiotic larvae (also have residual activity)

35
Q

what is an example of an amino acetonitrile?

A

monepantel

36
Q

what is an example of a spiroindole?

A

derquantel

37
Q

what is praziquantel used for?

A

tapeworm treatment

38
Q

what are some examples of flukicides?

A

triclabendazole
albendazole
closantel
oxyclozanide
nitroxynil

39
Q

what are the three dosing strategies for parasite control?

A

interval (regular intervals based on egg reappearance)
strategic (treat when parasite number are highest but no diagnostics involved)
targeted selective (treat using diagnostic factors)

40
Q

what are the three main influences of anthelmintic resistance development?

A

parasite biology
selection pressure (frequent drug use)
refugia (provides sensitive gene pool to dilute the resistant genes)

41
Q

how can anthelmintic resistance be diagnosed?

A

FEC reduction test - FEC before and after treatment a reduction <90% means there is resistance

42
Q

when does type 1 PGE occur?

A

August/September (late summer) in lambs

43
Q

what is the main parasite involved in type 1 PGE?

A

T. circumcincta

44
Q

what does the severity of PGE depend on in first season grazing lambs?

A

concurrent infections
nutritional status
immune response

45
Q

what is the main source of pasture contamination of eggs?

A

peri-parturient rise in egg output

46
Q

why does a peri-parturient rise in egg output occur?

A

reduced immunocompetence around parturition coupled with the seasonal reactivation of hypobiosed larvae

47
Q

what does the development of free living stages of nematodes depend on?

A

temperature
humidity
dispersal from faeces

48
Q

what is the to T. circumcincta during spring/summer?

A

spring (March/April) - overwintered L3 on pasture and peri-parturient rise lead to contamination
summer (May/June) - ewe is the main source of contamination, lambs now begin to graze and ingest L3
summer (June/July) - ambient temperature rises so egg development speeds up

49
Q

where is Nematodirus battus found in sheep?

A

small intestine

50
Q

what is the appearance of Nematodirus battus?

A

2cm long and tangled like cotton wool
can see large eggs in female uterus

51
Q

what is the lifecycle of Nematodirus battus?

A

eggs shed onto pasture in faeces, and develop to L3 within egg before hatching
L3 is ingested and develops to L4 which burrows into small intestine mucosa to develop to L5 which then emerges

52
Q

what is the pre-patent period of Nematodirus battus?

A

15 days

53
Q

what is the pathology caused by Nematodirus battus?

A

developing L5 destroys mucosa leading to catarrhal enteritis and villous atrophy meaning fluid/nutrient absorption is disrupted

54
Q

what are the clinical signs of Nematodirus battus?

A

sudden outbreaks of acute watery diarrhoea
inappetence, dehydration, abdominal pain
seen in lambs 4-12 weeks of age

55
Q

what is required for overwintered Nematodirus battus to hatch?

A

prolonged period of chill followed by increased day/night temperature

56
Q

when does Nematodirus battus cause disease?

A

May/June in 4-12 week old lambs…
hatching of overwintered L3 coincides with susceptible lambs that are grazing before immunity develops

57
Q

what is significant about the spread of Nematodirus battus?

A

lamb to lamb (as ewes develop strong immunity to it)

58
Q

what is the main clinical sign of Haemonchus contortus?

A

anaemia (and oedema)

59
Q

where is Haemonchus contortus found in sheep?

A

abomasum

60
Q

what is Haemonchus contortus also known as?

A

barber pole worm

61
Q

what type of lifecycle does Haemonchus contortus have?

A

typical trichostrongyle

62
Q

what is the pre-patent period of Haemonchus contortus?

A

three weeks

63
Q

what is the pathogenesis of Haemonchus contortus infections?

A

adults feed on blood and cause erosions of abomasal wall leading to severe haemorrhagic gastritis

64
Q

what is the main source of pasture contamination of Haemonchus contortus?

A

ewes (peri-parturient rise) as these worms don’t overwinter on pasture they only hypobiose within the ewe

65
Q

what are outbreaks of Haemonchus contortus seen?

A

late summer

66
Q

what colour are the anthelmintic drenches?

A
  1. white
  2. yellow
  3. clear
  4. orange
  5. purple
67
Q

what is clean pasture?

A

not grazed by sheep for previous 12 months

68
Q

what is safe pasture?

A

used the previous year but safe by beginning of June

Sheep... (15 decks)

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