Ascarids

Question 1

What are the physical characteristics of the typical Ascarid?

Answer 1

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

Question 2

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

Answer 2

1. Toxocara canis
2. Cervical alae

Question 3

What are the characteristics of an Ascarid egg?

Answer 3

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

Question 4

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?

Answer 4

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

Question 5

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

Answer 5

Within the ascarid egg

Question 6

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

Answer 6

1. Fecal - oral transmission
2. Paratenic host

Question 7

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

Answer 7

Duodenum

Question 8

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?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

30 - 35 days

Question 11

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)

Answer 11

10 - 15 days

Question 12

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

Answer 12

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

Question 13

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

Answer 13

4 - 30 days

Question 14

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

Answer 14

25 - 30 days

Question 15

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

Answer 15

1. Transplacental transmission
2. 25 - 30 days

Question 16

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

Answer 16

Resistant to sunlight and heat

Question 17

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?

Answer 17

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

Question 18

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

1. Larval migration
2. Adults in the GI tract

Answer 18

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

Question 19

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

Answer 19

Toxocara canis

Question 20

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?

Answer 20

25 - 30 days old

Question 21

Which antihelmintics work against Toxocara canis?

Answer 21

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

Question 22

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?

Answer 22

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

Question 23

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?

Answer 23

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

Question 24

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

Answer 24

50 - 60 days

Question 25

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

Answer 25

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

Question 26

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.

Answer 26

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

Question 27

Which antihelmintics would work against a Toxocara cati infection?

Answer 27

* BIG 3 * Emodepside

Question 28

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?

Answer 28

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

Question 29

What are some characteristics of Toxascaris leonina eggs?

Answer 29

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

Question 30

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"?

Answer 30

* **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

Question 31

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

Answer 31

1. Fecal-oral 2. Paratenic host

Question 32

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?

Answer 32

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

Question 33

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

Answer 33

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