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Flashcards in Ascarids Deck (33):

What are the physical characteristics of the typical Ascarid?

  • Anterior end
    • 3 lips
    • Long, narrow alae
  • Posterior end
    • NO bursa in the male


  1. Which parasite is this, genus and species?
  2. What is "A"?

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  1. Toxocara canis
  2. Cervical alae


What are the characteristics of an Ascarid egg?

  • Round to elliptical 
  • Thick shell
    • Brown/black
    • Pitted
  • Contents nearly fill the interior 

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Explain a little bit about the infective stage of an Ascarid: 

  1. Is there a direct or indirect life cycle?
  2. Is there an egg or fee-living L3?
  3. How can infection be acquired?

  1. Direct life cycle
  2. Egg (NO free-living L3)
  3. Transplacentally, transmammary, ingection, paratenic host


If there is no free-living L3, where can the L3 be found?

Within the ascarid egg


With Toxocara canis in particular, which modes of infection allow for somatic migration?

  1. Fecal - oral transmission
  2. Paratenic host


As for Ascarids like Toxocara canis, there is no free-living L3s - so where does the larvated egg hatch and release the L3s?



From ingestion of a Toxocara canis egg:

  1. How long until L3 is in the duodenum?
  2. How long until L3 is in the liver?
  3. How long until L3 is in the lung?

  1. 4 hours
  2. 24 hours from duodenum
  3. 12 - 24 hours from the liver
  4. 4 days TOTAL

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How does larval migration for Toxocara canis differ between the young and adults?

  • Young (< 12 weeks old)
    • Liver - lung - tracheal migration
  • Adults (> 12 weeks old)
    • Liver - lung - somatic migration


What is the pre-patent period of Toxocara canis within the Liver-lung-tracheal migration?

30 - 35 days


How long does it take Toxocara canis to get from the small intestine upon initial infection back to the small intestine after migration?

(Liver - lung - tracheal migration)

10 - 15 days


Toxocara canis that act through somatic migration - which tissues might they affect?

  1. Muscle
  2. Kidneys
  3. Liver
  4. Brain


How long does it take Toxocara canis to get from the small intestine upon intial infection to the somatic tissue after migration?

4 - 30 days


How long is the pre-patent period for Toxocara canis in a pup that acquired the infection transplacentally?

25 - 30 days


  1. What is the most common mode of transmission for Toxocara canis?
  2. What is the pre-patent period for this form of transmission?

  1. Transplacental transmission
  2. 25 - 30 days


Why might Toxocara canis eggs survive for years in the soil?

Resistant to sunlight and heat


  1. What clinical signs in a newborn pup are consistent with a Toxocara canis larval migration?
  2. What clinical signs are consistent with a Toxocara canis adult stage infection?

  • Larval migration
    • Abdominal pain
    • Fever
    • Cough
  • Adult stage
    • Poor doer
    • Pot belly 
    • Abdominal pain
    • Vomiting +/- diarrhea


On necropsy, what might be some of the findings with the following Toxocara canis infections:

  1. Larval migration
  2. Adults in the GI tract

  • Larval migration
    • Lung hemorrhages
    • Granulomas
  • Adults in the GI tract
    • Enteritis 


If this is the liver of a dog, what parasite is responsible?

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Toxocara canis


Prevention of Toxocara canis in pups can be achieved by deworming the pups prior to the Toxocara canis infection becomes patent.  This means deworming must occur before the pup is how old?

25 - 30 days old


Which antihelmintics work against Toxocara canis?

  • BIG 3
    • Avermectins
    • Fenbendazole
    • Pyrantel
  • Emodepside
  • Piperazine


  1. Which antihelmintic would be the best to give to a bitch prior to welping?
  2. Why might this be the most affective in this situation?
  3. What would be the protocol for this drug in this situation?
  4. Is this treatment a sufficient treatment for the bitch herself?

  1. Fenbendazole
  2. Fenbendazole specifically kills the hypobiotic larva that are activated during pregnancy
  3. Administer drug to the bitch from the 40th day of gestation up until 2 weeks after welping
  4. No - will need continuous treatment



  1. Name this parasite:
  2. What are its modes of infection?
  3. Which type of migration predominates in a young animal?
  4. What type of migration predominates in an older animal?

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  1. Toxocara cati
  2. Fecal-oral, transmammary, paratenic host
  3. Tracheal migration
  4. Tracheal migration (regardless of age)


What is the pre-patent period of Toxocara cati in tracheal migration?

50 - 60 days


  1. For Toxocara cati, what modes of infection have the shortest pre-patent period?
  2. How short can this pre-patent period be?

  1. Ingestion of a paratenic host & liver-lung-somatic migration
  2. 3 weeks


True or false:

  1. Toxocara cati is much more pathogenic than Toxocara canis.
  2. Adult animals with either one of these infections may be clinical ill - poor doer, anorexia, and have bouts of diarrhea.

  1. False: T. canis is more pathogenic than T. cati
  2. False: Adult animals are typically asymptomatic


Which antihelmintics would work against a Toxocara cati infection?

  • BIG 3
  • Emodepside


  1. What is the drug of choice to prevent transmission of T. canis from the bitch to her pups?
  2. What is the drug of choice to prevent transmission of T. cati from the queen to her kittens?
  3. What would be the protocol for that treatment in the queen?

  1. Fenbendazole
  2. Emodepside
  3. Treat 5 - 6 days prior to partuition


What are some characteristics of Toxascaris leonina eggs?

  • Oval to round
  • Colorless
  • Egg contains a single cell
    • Occupies only part of the shell


  1. What are the genus and species of the labeled eggs?
  2. What are egg characteristics of "a"?
  3. What are egg characterics of "b"?

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  • a.) Toxocara canis
    • Black/brown in color
    • Contents fill the shell
    • Pitted shell
  • b.) Toxascaris leonina
    • Colorless
    • Contents DO NOT fill the shell
    • Shell is smooth

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By which routes can an animal get infected by Toxascaris leonina?

  1. Fecal-oral
  2. Paratenic host


  1. Which of the Ascarids we learned about lays non-embryonated eggs?
  2. At what point do these become infectious?
  3. What is the pre-patent period of this parasite?

  1. Toxascaris leonina
  2. After 6 - 10 days in the environment
  3. 8 - 10 weeks


True or false:

  1. Toxascaris leonina is most commonly associated with its liver-lung-somatic migration.
  2. Toxascaris leonina is less pathogenic than Toxocara 

  1. False: Toxascaris leonina does not migrate via the trachea or somatically
  2. True: Toxascaris leonina does not undergo extensive migrations (liver-lung-etc.)