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Module 18: Ruminant Production > Nematodes of Sheep > Flashcards

Nematodes of Sheep Flashcards

1
Q

what are nematodes of the abomasum

A

Teladorsagia circumcincta

Haemonchus contortus

Trichostrongylus axei

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2
Q

what are nematodes of small intestine

A

Trichostrongylus vitrinus

Trichostrongylus colubriformis

Nematodirus battus

Nematodirus filicolis

Cooperia spp

Strongyloides papillosus

Bunostomum trigonocephalum

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3
Q

what are nematodes of large intestine

A

Esophagostomum venulosum

Trichuris ovis

Chabertia ovina

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4
Q

what are the nematodes of lungs

A

Dictyocaulus filarial

Muellerius capillaris

Protostrongylus rufescens

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5
Q

what are the most significant nematodes of sheep

A

Teladorsagia circumcincta:

  • Formerly Ostertagia circumcincta the ‘brown stomach worm’

Haemonchus contortus:

  • The ‘barber’s pole worm’
  • Different clinical picture

Trichostrongylus vitrinus:

  • ‘Black scour worm’
  • Northern Britain

Trichostrongylus colubriformis:

  • ‘Black scour worm’
  • Southern Britain

Nematodirus battus:

  • Has different epidemiology to other nematodes
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6
Q

what is the direct lifecycle of nematodes

A

Strongylid eggs (70–150 μm) usually hatch within 1–2 days

After hatching, larvae feed on bacteria and undergo two moults within feces to then develop to ensheathed third-stage larvae (L3s) in the environment (i.e., feces or soil)

The sheath (which represents the cuticular layer shed in the transition from the L2 to L3 stage) protects the L3 stage from environmental conditions but prevents it from feeding

Infection of the host occurs by ingestion of L3s

The infective L3 migrate onto pasture

During its passage through the abomasum, the L3 stage lose their protective sheath then transition to the L4 and pre-adult stages

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7
Q

what is the PPP for most nematodes

A

16-21 days

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8
Q

what are the ideal temperature for environmental stages

A

>5C, ideal 18-26C

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9
Q

what are the ideal humidity for environmental stages

A

min 50-60%

ideally >80%

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10
Q

what is hypobiosis

A

arrested development

unfavourable conditions for L3

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11
Q

how long do the parasites survive in the host

A

only a few months

few adults survive winter

unless hypobiosis

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12
Q

how long do the parasites survive on pasture

A

L3 are most resistant

  • Temperature extremes and desiccation, for many species infective L3 can survive up for 10-12 weeks
  • Some species they can survive for up to 12 months and not killed by frosts (T. circ)

Moisture

Temperature

  • Increased survival under temperate conditions vs tropical
  • Teladorsagia circumcincta can survive freezing
  • Haemonchus contortus cannot survive freezing
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13
Q

describe the environmental survival of the unembryonated egg of Haemonchus contortus

A

high susceptibility to cold and desiccation

high mortality <10C

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14
Q

describe the environmental survival of the embryonated egg of Haemonchus contortus

A

susceptible to cold and desiccation

low hatching in absence of moisture and/or at <10C

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15
Q

describe the environmental survival of the pre infective larvae of Haemonchus contortus

A

high susceptibility to cold and desiccaiton

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16
Q

describe the environmental survival of the infective larvae of Haemonchus contortus

A

optimum survival under warm and moist conditions

poor survival in dry climates (warm or cool) and sub freezing winter

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17
Q

describe the environmental survival of the unembryonated egg of Trichostrongylus colubriformis

A

intermediate susceptibility to cold and desiccation

high mortality at <5

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18
Q

describe the environmental survival of the embryonated egg of Trichostrongylus colubriformis

A

intermediate susceptibility to cold

low susceptbility to desiccation

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19
Q

describe the environmental survival of the pre infective larvae of Trichostrongylus colubriformis

A

susceptible to cold and dessication

high mortality at <5C

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20
Q

describe the environmental survival of the infective larvae of Trichostrongylus colubriformis

A

optimum survival under warm or cool moist conditions

poor survival over sub freezing winters

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21
Q

describe the environmental survival of the unembryonated egg of Teladorsagia circumcincta

A

low susceptibility to cold

intermed to desiccation

high egg viability at 0-10C

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22
Q

describe the environmental survival of the embryonated egg of Teladorsagia circumcincta

A

low susceptibility to cold and desiccation

hatching at <5C

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23
Q

describe the environmental survival of the pre infective larvae of Teladorsagia circumcincta

A

intermed susceptibility to cold

susceptible to desiccation

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24
Q

describe the environmental survival of the infective larvae of Teladorsagia circumcincta

A

optimum surivival under cool moist conditions and sub freezing winters

poor survival under warm, dry conditions

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25
Q

what is the annual cycle of eggs on pasture

A

overall ‘normal’, unchecked/untreated pattern of ewe and lamb nematode egg production over the 12 month annual cycle

  • At the start of the year there are some larvae that have survived the winter (dependent on weather and pasture management the previous year)
  • These surviving larvae start to die off
  • Ewes contaminate pasture during the peri-parturient rise (PPR) in egg output
  • Then when lambs start eating grass from 4-5 weeks old they start to multiply the nematodes, because they are naive so high shedders, and contaminate pasture further
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26
Q

what is the annual cycle of ewe fecal egg output and larvae on pasture

A

PPR is when there is a rise in FEC in ewes around parturition, lasting from a couple of weeks before lambing to 6-8 weeks after lambing

Adult ewes have good immunity unless immune-suppressed

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27
Q

what is the periparturient rise (PPR)

A

Due to reduced immunity:

  • Physiological associated with pregnancy?
  • Re-distribution of nutrition of fetal develop and milk production

Results from:

  • Renewed development of hypobiotic larvae into laying adults
  • Increases susceptibility to further infection from pasture
  • Increase in fecundity of adult female worms
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28
Q

what is the annual cycle of lamb and ewe fecal output and larvae on pasture

A
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29
Q

what does rate of contamination build up depend on in pasture (3)

A
  1. climatic conditions
  2. lamb anthelmintic treatments
  3. grazing management (pasture rotation)
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30
Q

when do hypobiotic larvae become an issue for

A
  1. store lambs
  2. breeding replacements
  3. pregnant ewes
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31
Q

what are the clinical signs of PGE

A

Reduced weight gain

Reduced feed intake (60-70% of reduced DLWG)

Poor body condition

Open fleece

Diarrhea (variable) — fecal staining

Dehydration

Death

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32
Q

what are the ddx for PGE

A

Coccidiosis (diarrhea/ill thrift)

Nematodirosis (diarrhea/ill thrift)

Selenium deficiency (ill thrift)

Cobalt deficiency (ill thrift)

Nutritional:

  • Lush grass (diarrhea)
  • Poor quality/quantity of feed (ill thrift)
  • Ruminal acidosis (diarrhea +/- poor DLWG)
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33
Q

what are the causes of clinical signs in PGE

A

GIT inflammation due to immune response

Mucosal damage (short term +/- long term)

Due to larvae as well as adult nematodes

Anorexia

Malabsorption

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34
Q

what does the morbidity and mortality depend on with PGE

A

Species of GI nematode(s) (GIN)

Infective load

Host immunity

Mortality can be high if untreated

Subclinical effects on DLWG and feed conversion are significant

Distribution of infection

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35
Q

what groups are susceptible to PGE

A

Young, non-immune animals

Adult, immunocompromised animals

Those exposed to a high infection pressure from a heavily L3-contaminated environment

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36
Q

what do the early stages of PGE look like

A

Reduction in weight gain might be the only notable sign

60-70% of the reduction in growth rate in parasitized lambs can be attributed to reduced feed intake

Affected lambs develop low BCS, diarrhoea, an unkept ‘open’ fleece, dehydration and death

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37
Q

describe the clinical picture of Teladorsagia circumcincta

A

abomasum

anorexia

poor growth

scour

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38
Q

describe the clinical picture of Trichostrongylus spp

A

small intestine

anorexia

poor growth

scour

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39
Q

describe the clinical picture of haemonchus contortus

A

abomasum

anorexia

anemia

death

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40
Q

describe the clinical picture of nematodirus battus

A

small intestine

anorexia

severe scour/dehydration

death

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41
Q

when does Teladorsagia circumcincta PGE usually occur

A

summer and autumn

42
Q

what does Trichostrongylus spp cause

A

dark scour

anorexia

poor skeletal growth

chronic ill thrift

protein leakage

electrolyte and mineral imbalances

43
Q

when does Trichostrongylus spp PGE occur

A

autumn and winter

44
Q

what is the lifecycle of nematodirus battus

A

Larvae develop in the egg (usually 8-9 months)

The majority of strains require a period of cold priming before they hatch

  • Once period of warm (+ damp) after cold met —> mass hatch

Mass contamination of pasture in a very short period of time

If grazing lambs (over 5 weeks old) are present on pasture when this mass hatch occurs, it can result in mass infection and severe disease in those lambs

45
Q

what does the acute onset of nematodirus battus look like

A

profuse watery scour

dehydration

dull

abdominal pain

rapid weight loss

death

poor mineral absorption – poor skeletal growth

46
Q

when does nematodirosis occur

A

in spring (+ autumn)

47
Q

how is nematodirus battus treated

A

all nematode anthelmintics

usually benzimidazoles

48
Q

what is special about goats and nematodes

A

Develop no or minimal immunity

Multiply pasture contamination

High drug metabolism so need higher doses

Except Levamisole (high doses of levamisole are dangerous in goats and sheep)

Fast track development of anthelmintic resistance

  • Due to the lack of immunity, which results in increased need for treatments and rapid metabolism of those treatments, goats are effective mediators for the rapid development of anthelmintic resistance in the nematodes that infect them

Many of the same species of nematode infect goats as shee

49
Q

how are nematodes diagnosed (6)

A
  1. history and clinical signs
  2. fecal worm egg count (FWEC)
  3. PM
  4. pepsinogen
  5. species ID (PCR)
  6. FAMACHA (H. contortus)
50
Q

how is fecal worm egg counts done

A

Modified McMaster technique

Dilute feces then multiply result

Give eggs per gram (epg)

Ideally 10 individual samples (15 for fecal egg count reduction test (FECRT)

Can be pooled (ask for them individually though)

Fresh samples

51
Q

what egg is this

A

trichostrongylid

52
Q

what species is this

A

trichostrongylus

53
Q

what sp is this

A

coccidia

54
Q

what species is this

A

nematodirus

55
Q

what are the pros for using FWEC

A

Predict pasture contamination

Determine pattern of infection on individual farms

Encourage farmer/vet interaction

FECRT

Nematodirus battus diagnosis

56
Q

what are the cons to using FWEC

A

Cannot speciate Trichostrongyle style eggs

FWEC not representative of burden (ex. H. contortus)

  • These nematodes produce so many eggs that eggs from other nematodes become insignificant

Not related to lamb performance (resilience vs resistance)

  • Some lambs will have high burdens and high FWEC but good growth rates (be resilient) and some lambs will have low burdens/FWEC but low growth rates (resistant – they are using nutritional reserves to attack the wo
57
Q

how do intrepret FWEC

A

in conjuction with

CS

weather

grazing history

58
Q

how do you diagnose nematodes on PM

A
  1. pallor
  2. ascites
  3. abomasum (swirling, H. contortus or T. circumcincta, glandular hypertrophy T. circumcincta)
  4. small intestine (catarrhal inflammation or mucosal thickening, N. battus worms)
  5. total worm counts
59
Q

what are the uses of nematode pharmaceuticals

A

Treat disease

Metaphylactic treatment of others in a group

Prevent build up of pasture contamination

Promote good growth rates

60
Q

what is the mechanism of action of benzimidazoles

A

binds β-tubulin

61
Q

what are benzimidazoles active against

A

cestodes, nematodes +/- trematodes

62
Q

what are examples of benzimidazoles

A

lbendazole (+ liver fluke)

Fenbendazole

Mebendazole

Triclabendazole (liver fluke not worms)

Febantel, netobimin and thiophanate — probenzimidazoles need liver activation

63
Q

what is the mechanism of action of imidazothiazoles

A

spastic paresis (ganglion blocking)

64
Q

what are imidazothiazoles active against

A

Active against nematodes (not inhibited larvae)

65
Q

what are examples of imidazothiazoles

A

levamisole

66
Q

what is the mechanism of action of MLs

A

flaccid paralysis (GABA chloride channels)

67
Q

what are MLs active against

A

Active against nematodes and arthropods

68
Q

what are examples of MLs

A

Avermectins (Ivermectin, doramectin, abamectin, eprinomectin)

milbemycins (moxidectin)

69
Q

what does persistent activity of MLs depend on

A

relies on lipophilic characteristics so body fat presence

70
Q

what is the mechanism of action of amino acetonitrile derivatives

A

spastic paralysis (acetylcholine receptors?)

71
Q

what are examples of amino acetonitrile derivatives

A

monepantel

72
Q

what are amino acetonitrile derivatives active against

A

nematodes

73
Q

what is the menchanism of action of Spiroindoles

A

spastic paralysis (acetylcholine receptors)

74
Q

what are examples of spiroindoles

A

derquantel

75
Q

what are spiroindoles active against

A

nematodes

76
Q

what are narrow spectrum anthelmintics

A

closantel and nitroxynil effective against H contortus only

BZ used for N battus

77
Q

what are long acting anthelmintics

A

doramectin

moxidectin

78
Q

what are anthelmintics use in lambs to control nematodes (5)

A
  1. regular routine treatments often every 3-4 weeks
  2. therapeutic treatments
  3. FWEC guided treatments
  4. reduce pasture contamination
  5. targeted treatments or targeted selective treatments
79
Q

what are the problems with dose and move

A

promote resistance

80
Q

what are the alternatives to dose and move

A

leave a proportion untreated (often 10%)

dose a few days before move (4-5 days if action is <3 days)

81
Q

what are areas to target for prevention

A

eggs shedding from ewes in spring

and buildup in summer of pasture larvae

82
Q

how do you prevent the ewe periparturient rise

A
  1. Nutrition
  • Good immune response
  • Selective breeding for resistance
  • Low FWEC
  1. clean/safe grazing
  2. anthelmintics
  • short acting
  • long acting
83
Q

how do you graze ewes in a clean/safe grazing pasture

A

Newly planted pasture/rotation with arable

Rotation with cattle

84
Q

how can anthelmintics be used to prevent ewe peripartient rise

A

Repeated 3 weeks after lambing (but rarely are) as the PPR extends 6-8 weeks after lambing

Long acting treatment of ewes can reduce need to treat lambs, but can increase risk of anthelmintic resistance developing, due to a long tail off when the drug is at sub-therapeutic levels and sub-therapeutic transmission of moxidectin to lambs in milk

85
Q

how do prevent lamb exposure to nematodes (5)

A
  1. newly planted pasture
  2. rotation with cattle or mixed grazing
  3. rotation with dry adult ewes (not rams)
  4. strategic treatments
  5. bioactive forages
86
Q

how can a newly planted pasture reduce exposure to lambs

A

Reducing exposure to infectious larval stages of GI nematodes will maintain the best production and animal health levels, however this can be difficult to do in intensively farmed sheep flocks

Good as part of arable rotation

Providing clean pasture at 3 week intervals reduces re-infection rates, however this is not ideal for promoting good grass growth and utilization (paddock rotation for good grass use promotes the nematode cycle and is one of the major issues with this system)

87
Q

how can roration with cattle or mixed grazing prevent lamb exposure

A

Many cattle and sheep farms

But, cattle are capable of multiplying up Haemonchus contortus and calves can cycle Nematodirus battus

Low contamination pasture can become contaminated very quickly, so must be used with care and not wasted

88
Q

how does rotation with dry adult ewes reduce exposure of lambs

A

Only after weaning

Maintain/develop immunity

Don’t use rams!

89
Q

how can strategic treatments reduce exposure to lambs

A

Strategic treatments can be used by treating lambs early, as they starting to shed eggs, to prevent pasture contamination

However, this increases the pressure for development of anthelmintic resistance because there are low numbers of nematodes on pasture, so a low proportion of nematodes not exposed to anthelmintic (in refugia) to provide susceptible genes to dilute those of the resistant nematodes that survive treatment

90
Q

how can bioactive forages be used to reduce exposure to lambs

A

Bioactive forages, such as chicory have debatable effect on reducing GI nematode burdens in sheep

91
Q

how can you reduce lamb susceptibility

A

nutrition

selective breeding

92
Q

how can selective breeding reduce lamb susceptibility

A

Resistance

  • Low burdens and egg output
  • Low FWEC (normally carried out in the mid and late grazing season of their first year of life)
  • These animals can have low growth rates when they are exposed to highly contaminated pasture, because they are using reserves to tackle the infection rather than grown

Resilience

  • High growth rates despite GI nematodes
  • Although this can be more difficult as there can be many factors influencing growth rates

IgA testing

  • Useful immune responses but also good growth rates when exposed to nematodes. This test is carried out on saliva or blood, saliva is more user friendly for farmers, whereas blood is more reliable
93
Q

how can quarantine reduce nematodes

A

avoid buying or moving resistant worms onto a farm

Effective treatment

Minimum of two anthelmintics active against all pathogenic gastrointestinal nematodes (from different anthelmintic groups

The use of multiple active ingredients reduces the number of surviving nematodes, as most will only be resistant to one active ingredient

Ideally these animals should have a FECRT carried out, or even just a post treatment text 10-14 days later

One after the other —> NEVER mix

Given 48 hours before turnout to ‘dirty’ pasture

Pasture that is likely to be contaminated with nematodes from sheep already on the farm, these will dilute any resistant nematodes in the new/returning stock

94
Q

what are the lungworm species

A

Dictyocaulus filarial

Muellerius capillaris

Protostrongylus rufescens

95
Q

what is the lifecycle of Muellerius capillaris

A

indirect lifecycle – molluscs

96
Q

what are important cestodes

A

Hydatid disease (Echinococcus granulosus)

Cysticercus tenuiocollis (Taenia hydatigena)

Monezia spp.

Cysticercus ovis (Taenia ovis)

Coenurosis (Taenia multiceps)

97
Q

what is the signficance of Coenurosis (Taenia multiceps)

A

dog definitive host

cysts in CNS

gid

98
Q

what is the signifiance of Cysticercus ovis (Taenia ovis)

A

dog definitive host

cysts in liver, muscles

abattoir condemnations – sheep measles

99
Q

what is the signifiance of Monezia spp.

A

sheep definitive host

minimal clinical effect

unless obstruction

100
Q

what is the significance of Cysticercus tenuiocollis (Taenia hydatigena)

A

dog definitive host

cysts in liver, omentum, mesentery

101
Q

what is the significance of Hydatid disease (Echinococcus granulosus)

A

dog definitive host

cysts in liver and lungs

zoonotic from dogs

102
Q

how are cestodes controlled

A

worming dogs (praziquantel)

control dog movements

remove carcasses

dont feed raw sheep meat to dogs

Module 18: Ruminant Production (25 decks)

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