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Flashcards in Strongyles Deck (70):

What is the level of egg develpment within the female strongyle?



What typically accompanies the large buccal cavity of the "true" strongyle?

Corona radiata


  1. What is the function of the male spicule?
  2. What is the function of the male bursa?

  1. Spicule dilates the vulva
  2. Copulatory bursa holds on the female


List 4 life cycle characteristics of the true strongyle:

  1. Direct life cycle
  2. Free-living L3
  3. Mainly infect herbivores
  4. Adults mostly infect GI tract


Which is most pathogenic, the large or small strongyles?

Large strongyles


Strongyle-type eggs contain an embryo within what stage of development when passed in the feces?



How many teeth do each of the following species have:

  1. Strongylus edentatus
  2. Strongylus vulgaris
  3. Strongylus equinus

  1. 0
  2. 2
  3. 3


This parasite is of what species and genus?

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Strongylus vulgaris


This parasite is of what species and genus?

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Strongylus equinus


This parasite is of what genus and species?

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Strongylus edentatus


Adult strongyles will infect which parts of the body?

  1. Cecum
  2. Colon


Explain the pathway of the large strongyles eggs into their infective L3 stage?

Where does this process occur?

  1. L1 passed in the feces
  2. L1 hatches
  3. Molts into L2
  4. Molts into sheathed L3

This process occurs in the environment.


Being sheathed, the L3 is resistant to what?

  1. Dry 
  2. Cold 


Which 3 things allow the strongylus eggs the migrate up vegetation?

  1. Positive phototropism
  2. Negative geotropism
  3. Moisutre (dew)


How does a horse get infected with strongylus?

Ingests the free-living L3 on vegetation 


Once infected, the L3 unsheaths and penetrates the intestinal mucosa.  Following this, the larva molts into an L4.  

  1. Where does this molting occur?
  2. How long does this molting take?

  1. Submucosa of the intestine
  2. About 1 week


  1. Strongylus vulgaris L4s cannot penetrate which layer of the vasculature?
  2. This causes them to stay within which layer instead?

  1. Internal elastic lamina
  2. Intima

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These rapidly migrating larva can reach the cranial mesenteric artery within what sort of time period?

2 - 3 weeks


L4s continue to migrate within the intima of the vasculature for about how long after reaching the cranial mesenteric artery?

2 - 4 months


  1. After 2 - 4 months of migrating in the intima, L4s are carried by the blood stream to the small capillaries of what?
  2. Migration to this area causes what next sequence of events?

  1. Subserosal layer of the intestinal
  2. Occludes the smalla arteries there -> Vascular walls become inflammed -> Vascular walls are destroyed -> Larvae are liberated -> Larvae enter surrounding tissue -> Larva are encapsulated there and will molt into L5s -> L5s rupture out of nodules -> Adults form in the cecum & colon


What are the pre-patent periods for the following parasitic species:

  1. Strongylus vulgaris
  2. Strongylus edentatus
  3. Strongylus equinus

  1. 6 months
  2. 6 - 11 months
  3. 9 months


What problems can larval migration of S. vulgaris cause?

  1. Arteritis
  2. Thrombosis
  3. Aneruysms
  4. Decreased gut motility
  5. Predisposes to colic


  1. Which is the more common Strongylus infection - the acute syndrome or verminous colic?
  2. Which is more severe?

  1. Verminous colic
  2. Acute syndrome - can end in death 2 - 3 weeks PI


What are clinical signs of the acute syndrome?

  1. Fever
  2. Abdominal discomfort
  3. Diarrhea
  4. Anorexia / weight loss
  5. Depression / lethargy


  1. What are the clinical signs of verminous colic?
  2. Which of these signs differs from the acute syndrome?

  1. Anorexia, weight loss, diarrhea / constipation, rough hair coat, anemia
  2. Anemia & rough hair coat


Which strongylus larva migrates retro-peritoneally?

Strongylus edentatus


  1. Where does the molting of S. edentatus larva into L4s take place?
  2. Where does the molting of S. vulgaris larva into L4s take place?

  1. Hepatic nodules
  2. Submucosa of the cecum/colon


  1. Which strongylus species leaves the liver via the hepatic ligaments?
  2. What stage larva is this living the liver?

  1. Strongylus edentatus
  2. L4


Which strongylus species has the potential of causing a hemorrhagic peritonitis?

Strongylus edentatus

Image: Strogylus edentatus, immature adults, under the peritoneum

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Where does the molt of Strongylus equinus from L3 into L4 take place?

L3 -> L4 occurs within nodules of the large intestine (cecum & colon)


  1. How does S. equinus get to the liver?
  2. How does S. edentatus get to the liver?

  1. S. equinus migrates through the peritoneal cavity
  2. S. edentatus migrates through the hepatic portal vein


Where does S. equinus molt into L5?

Peritoneal cavity


Explain the migration path of Strongylus equinus:

L3 molts into L4 within nodules of large intestine -> L4 migrates through the peritoneal cavity to the liver -> L4 migrates within the liver parenchyma for 2 months -> L4 migrates back through the peritoneal cavity -> Molts into L5 -> L5 migrates into the large intestine -> Molt into adult form

Pre-patent period: 9 months


What types of clinical signs can develop with a heavy infection of Strongylus equinus?

  1. Liver hemorrhage
  2. Colic
  3. Anorexia
  4. Lethargy


Select the correct statement:

a.) Anthelmintics against large strongyles >> effective than for small strongyles

b.) Anthelmintics against small strongyles >> effective than for large strongyles

a.) Anthelmintics against large strongyles >> effective than for small strongyles


What are some characteristics of the life cycle of the small strongyles?

  1. Direct life cycle
  2. Pre-patent period: 6 - 8 weeks
  3. L3 can become hypobiotic


What type of feeders are the small strongyles?

Plug feeders +/- blood sucking


  1. What is the significance of a strongyle-type egg in a foal less than 6 weeks old?
  2. What is the significance of a strongyle-type egg in a foal between 6 weeks and 6 months of age?
  3. What is the significance of a strongyle-type egg in a foal older than 6 months of age?

  1. Likely ingested from mare feces; just passing through
  2. Likely infection with small strongyles
  3. Likely infection with BOTH small and large strongyles


When checking a foal at greater than 6 months of age, which strongyle will represent the majority of the eggs you see?

Small strongyles


Define cyathostomiasis.

A clinical syndrome associated with the mass emergence of larva from mucosal cysts (can persists there for weeks - years)


What are the clinical, potentially fatal, signs of cyanthostomiasis?

  1. Fever
  2. Persistant diarrhea
  3. Weight loss
  4. Hypoalbuminemia


What will be your go-to anthelmintic for a cyathostomiasis infection?



What supportive care might you try when an animal has larval cyathostomiasis?

  1. Corticosteroids
  2. Anti-diarrheals
  3. Fluid therapy maybe


What are the goals of selective therapy of strongyles?

  1. Use drugs in a way that will slow resistance
  2. Avoid clinical signs (decrease eggs on the pasture)


What 2 factors does selective therapy rely upon?

  1. Uneven distribution of eggs
  2. High shedders will consistently be high shedders


According to the parasitologist rule, what percentage of horses shed what percentage of the strongyle eggs?

20% shed 80% of the eggs


What should be your eggs per gram treatment threshold?

100 - 300 epg (typically 200 is the threshold)


When performing a fecal egg count reduction test, what percentage of reduction is sufficient?

95% or higher


What tests do you perform to find out the following information?

  1. Whether or not my horse has parasites
  2. Which horses are the highest shedders
  3. Whether or not a drug is working on my farm

  1. Fecal float
  2. McMaster
  3. Fecal egg count reduction test


  1. Which parasite is of most concern in adult horses?
  2. Which parasite is of most concern in young horses?

  1. Small strongyles (cyathostomias)
  2. Parascaris equorum


Which part of the body does Oesophagostomum infect?

Large intestine


A re-infection with Oesophagostomum is associated with the formation of nodules within the GI tract.  Rarely, these nodules can rupture.  What problems might a rupture cause?

  1. Mucosal rupture : ulcerative colitis
  2. Serosal rupture : peritonitis


What is the nicename for Chabertia ovina?

"Large mouthed bowel worm"


What are the life cycle characteristics of Chabertia?

  1. Direct life cycle
  2. Can undergo hypobiosis
  3. Pre-parent period of 6 weeks


  1. How does Chabertia feed off of the host?
  2. Why might this be?

  1. Plug feeding
  2. No teeth


  1. Name this parasite:
  2. What animals might it infect?

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  1. Chabertia ovina
  2. Small ruminants (sheep, goats)


Which part of the body does Chabertia infect?



What are the nodular worms of ruminants?

  1. Oesophagostomum
  2. Chabertia


What is the nickname for Stephanurus dentatus?

Swine kidney worm


Is Stephanurus dentatus found within the midwestern states?

No - larvae CANNOT survive freezing temperatures


Which parasite can gain entry into the body via SKIN PENETRATION?

Stephanurus dentatus


Via what routes of infection does Stephanurus dentatus infect?

  1. Penetration of L3 through skin
  2. Paratenic host
  3. Ingestion of L3


  1. How long does Stephanurus migrate through a pig's liver?
  2. What might the migration do to the liver grossly?

  1. 2 - 9 months
  2. Cause liver fibrosis


What is the pre-patent period of Stephanurus dentatus?

9 - 16 months


Stephanurus dentatus migrates retro-peritoneally from the liver and ends up in what locations?

  1. Kidney wall
  2. Ureters


Which parasites might cause these lesions within the liver of a pig?

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  1. Stephanurus dentatus
  2. Ascaris suum


Which bodily product would house the eggs of Stephanurus dentatus?



This paraiste is housed within the perirenal fat of a pig.  Which parasite is it?

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Stephanurus dentatus


What would be your drug of choice for Stephanurus dentatus?