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Sheep... > Clinical parasitology (Yr 4) > Flashcards

Clinical parasitology (Yr 4) Flashcards

1
Q

what would resistance to an anthelmintic be defined as?

A

<95% drug efficacy

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2
Q

what are the main nematodes causing disease in sheep?

A

Nematodirus battus
Teladorsagia circumcincta
Trichostrongylus spp.
Haemonchus contorts
Dictyocaulus filaria

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3
Q

what age is Nematodirus battus seen in sheep?

A

6-12 week old lambs in late spring

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4
Q

what is the main clinical sign of Nematodirus battus?

A

acute severe diarrhoea

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5
Q

what age is type 1 Teladorsagia infection seen?

A

first season grazing lambs from mid summer onwards

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6
Q

what the is type 2 Teladorsagia seen?

A

yearling in winter months (due to emergence of hypobiotic larvae

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7
Q

what age is Trichostrongylus seen?

A

lambs/replacements in late summer to autumn

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8
Q

what is the main clinical sign of Trichostrongylus infection?

A

black scour

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9
Q

what is the main clinical sign of Haemonchus contortus?

A

acute regenerative anaemia

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10
Q

what nematodes have a typical trichostrongyle lifecycle?

A

Telodorsagia circumcinta
Trichostrongylus spp.
Haemonchus spp.

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11
Q

what is the typical trichostrongyle lifecycle?

A

L3 (infective) is ingested
mature into L4 and adults
eggs passed in faeces
moult to L1, L2 and L3
L3 are eaten or overwinter

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12
Q

what is the pre-patent period of nematodes with a typical trichostrongyle lifecycle?

A

3 weeks

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13
Q

why does egg output from ewes rise around lambing?

A

peri-parturient rise (drop in immunity around lambing)

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14
Q

where does most of the eggs come from for Haemonchus infections?

A

from the ewes (doesn’t overwinter very well)

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15
Q

when do Trichostrongylus infections peak?

A

late summer

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16
Q

what is the main way Haemonchus survive over winter?

A

hypobiosis

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17
Q

how do lambs become infected with Nematodirus battus?

A

eggs shed by lambs previous year remain on pasture and will infect the next crop of lambs

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18
Q

what causes hatching of Nematodirus battus?

A

prolonged period of chill followed by increased temperature cause mass hatching on master (this coincides with lambs being turned out)

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19
Q

do sheep develop resistance to nematodes?

A

yes - if they have been exposed they will develop resistance at about 6 months old

20
Q

what are the classes of anthelmintics?

A
  1. benzimadazoles (white)
  2. levamisole (yellow)
  3. macrocytic lactones (clear)
  4. amino-acetonitrile (orange)
  5. spiroindoles (purple)
21
Q

how do benzimadazoles work?

A

prevent glucose uptake (ovicidal)

22
Q

how does levamisole work?

A

causes paralysis of parasites (ovoidal)

23
Q

how do macrocyclic lactones work?

A

block GABA channels to cause paralysis

24
Q

what endoparasites will benzimidazoles kill?

A

nematodes
tapeworms
fluke (albendazole)
Nematodirus battus (little resistance)

25
Q

what parasites will macrocyclic lactones kill?

A

nematodes and mites (injectables)

26
Q

how can you test for resistance to anthelmintics?

A

faecal egg count reduction (compare faecal egg count before and after dosing, a reducing of <95% means that there is resistance)
drench test (FEC after dosing)

27
Q

what are the SCOPS principles?

A

always make sure treatment is effective
reduce dependance on anthelmintics through management
avoid bringing in resistant worms through biosecurity
minimise selection for resistant worms when treating

28
Q

what nematode do sheep not gain resistance to?

A

Haemonchus spp.

29
Q

if treating at lambing time for nematodes, should you treat all the ewes?

A

no, treat the ones that will have the highest worm output during their peri-parturient rise such as triplets, thin ewes, ewe lambs…

30
Q

what nematode is there a vaccine against?

A

Haemonchus (barbervax)

31
Q

what clinical sign can be used as a guide for dosing Hameonchus?

A

pallor of eye MM (anaemia) - this is called the FAMANCHA test

32
Q

how often should you sample lambs for FEC?

A

2-4 weeks

33
Q

what nematode can FEC not be used for a diagnosis tool to guide dosing?

A

Nematodirus battus

34
Q

why can’t FEC be used as an accurate way of deciding to dose Nematodirus?

A

the larval stages cause disease, so FEC won’t determine how many larva are present only adults

35
Q

how should quarantined sheep be treated for nematodes?

A

dose with class 4 or 5 and hold inside for 2 days then place on contaminated pasture so they pick up the infections of the farm

36
Q

how can selection for anthelmintic resistance be minimised?

A

worm when majority of worms are in the sheep and not on pasture (eg. don’t dose at lambing)
don’t dose and move (leave on contaminated pasture for a few days)
only treat thin, young or immunocompromised sheep
avoid long acting products

37
Q

when do we want to dose sheep in relation to the amount of parasites on pasture?

A

when lowest number are on pasture, as this is a massive selection pressure

38
Q

which cestode is zoonotic?

A

Echinococcus granulosus

39
Q

what is the primary host for the majority of cestode infections?

A

dog

40
Q

what is the clinical significance of Taenia hydatigena?

A

cysts in liver causing condemnation

41
Q

what is the clinical significance of Taenia ovis?

A

cysts cause muscle damage and condemnation

42
Q

what is the clinical significance of Taenia muliticeps?

A

cysts cause neurological disease in sheep

43
Q

what is the clinical significance of Echinococcus granulosus?

A

cysts in liver/lungs cause condemnation
zoonotic

44
Q

what is the control strategy for Monezia expansa?

A

worm sheep with benzimadzoles

45
Q

how are Taenia spp. and Echniocccus controlled?

A

treating dogs with praziquantel to kill adults
no dogs faeces on pasture or scavenging of carcasses

Sheep... (15 decks)

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