Strongylus spp Flashcards

1
Q

What are the main features of the Strongylus life cycle?

A
  • Direct
  • Migratory – in contrast to the cyathostomins
  • Infective stage is L3
  • Because they undergo migration they have a considerably longer PPP of months long
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2
Q

Name 3 Strongylus spp

A

Strongylus edentates
Strongylus equinus
Strongylus vulgaris

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3
Q

Describe the morphological features of Strongylus vulgaris

A
  • The mouth is a cup shape = buccal cavity
  • The the base of the buccal cavity there are two rounded structures which are teeth
  • 1.5-2.5cm long
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4
Q

How does the morphology of S.edentates differ from S.vulgaris?

A
  • Also has a buccal cavity but no teeth
  • 2.5-5cm long
  • Has a dorsal gutter visible in the head
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5
Q

Describe the life cycle of Strongylus vulgaris

A
  • Ingested as L3, they go into the SI/LI and penetrate the mucosa before migrating
  • Whilst migrating they are also developing so L4 would be found in the mesenteric arteries
  • They then return to the gut where they emerge in the large intestinal lumen
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6
Q

Where is the predilection site of migration for Strongylus vulgaris?

A

Cranial mesenteric arteries

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7
Q

The time between ingestion of an L3, migration and returning to the gut and being found as egg producing adults would be how long for Strongylus vulgaris?

A

PPP = 6 months

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8
Q

Where is the predilection site for Strongylus edentatus?

A

Flanks and hepatic ligaments

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9
Q

The time between ingestion of an L3, migration and returning to the gut and being found as egg producing adults would be how long for Strongylus edentatus?

A

PPP = 10 month

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10
Q

Where is the predilection site for Strongylus equinus

A

Liver then pancreas

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11
Q

The time between ingestion of an L3, migration and returning to the gut and being found as egg producing adults would be how long for Strongylus equinus?

A

PPP = 8 months

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12
Q

Describe the pathology of disease caused by Strongylus vulgaris

A
  • Migrating larvae (L4) have a pre-deliction for the cranial mesenteric artery
  • Can cause a non-strangulating infarction secondary to larvae in cranial mesenteric arteries
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13
Q

What are some epidemiological similarities between Cyathostomin and Strongylus?

A
  • Horses do not develop strong immunity
  • Over dispersion – small proportion of the host population carries the majority of the parasite population
  • Egg to L3 development is similar, L3 survival over winter etc
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14
Q

What are some epidemiological differences between Strongylus compared to Cyathostomin?

A
  • NO hypobiosis
  • Longer PPP due to somatic migration (≥6 months)
  • Lower levels of infection are needed to cause disease
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15
Q

What are 3 goals of parasite control?

A
  • To minimise the risk of parasite-associated disease
  • To reduce parasite transmission e.g reduce parasite egg shedding
  • To preserve drug efficacy and avoid further development of drug resistance
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16
Q

How can pasture be manages to control parasites?

A
  • ‘Poo picking’
  • Pasture rotation: do not over graze or use pasture for horses year on year
  • Mixed species grazing
  • ‘Clean pasture’ at turnout
  • Harrowing (only effective in very dry, warm climates): turn the soil, bringing the larvae to the top where the sun dries them out
17
Q

Which anthelmintics can be used to treat Strongyles?

A
  • Moxidectin
  • Ivermectin
  • Fenbendazole and Pyrantel also but less FEC reduction as there is resistance
18
Q

Why is moxidectin the drug of choice for strongyles?

A

Targets hypobiosed encysted larvae

19
Q

Treatment with anthelmintics should be targeted towards which animals?

A

High shedders - high FEC

- Reduce pasture contamination

20
Q

What are the challenges of managing Strongyles on livery yards and studs

A
  • Multiple owners
  • Restricted grazing
  • High turnover (+/- quarantine)
  • Young horses
  • Visiting mares and foals
  • Economics
21
Q

Name the worm spp that contributes to the damage caused by other adults worms of other spp but is rarely pathogenic on their own

A

Triodontophorus spp