Nematodes (Ascaridida)

Question 1

Describe the life cycle of Ascaris suum

Answer 1

• Huge adult, up to 30 cm with 3 large lips L# hatches in the stomach or small intestine
• Then it enters the wall of the cecum and colon and proceeds to the liver for several days moving into the portal vein
• Tunnels around the liver for a few days, migrating to the lungs via CVC, heart and pulmonary capillary
• Bursts through pulmonary capillaries and migrates up bronchial tree–> Small intestine

Question 2

What are the common pathology features of Ascaris suum?

Answer 2

• Mechanical trauma and hypersensitivity reaction
• Liver heals by fibrosis -> milk spots
• Lungs–> damage results in “thumps” (audible respiratory effort) and coughing
• Can cause diarrhea and interfere with weight gain

Question 3

How is Ascaris suum treated?

Answer 3

Hygromycin B, piperazines, dichlorvos, fenbendazole, levamisoles, ivermectin, doramectin, and pyrantel

Treating and cleaning sows with warm soapy water 2 weeks before moving to farrowing crates

Treating again at weaning

Adding pyrantel to feed prevents migration and establishment of A. suum infections as pyrantel is the only approved drug to treat larvae immediately after they hatch in the small intestine

Question 4

What two ascarids are models for embyronology?

Answer 4

Parascaris equorum has 2 germline chromosomes and P. univalens has only a single pair

Question 5

Describe the life cycle of Parascaris equorum

Answer 5

Per os transmission to the foal

Larvae hatch and burrow into the small intestine and are carried to the liver by the portal vein

After migrating through the hepatic tissues, it enters the hepatic vein and is carried to the CVC, heart, and pulmonary arteries where it enters the alveolus

Molts in lung and undergoes tracheal migration

Per os transmission to the foal

Question 6

What is the pathology feature of Parascaris equorum?

Answer 6

1st wave inflict mechanical damage

Second wave causes a hypersensitivity reaction

Heavy: Enteritis and subnormal growth

Produces malnourished undersized and sickly individuals with little stamina

Question 7

How is Parascaris equorum treated? Resistance?

Answer 7

• Treatment
  
  • Piperazine (100 mg/kg), fenbendazole (10 mg/kg), pyrantel (6.6 mg/kg), ivermectin (0.2 mg/kg), moxidectin (0.4 mg/kg)
  • Pyrantel is used as a feed additive
• Resistance
  
  • Macrocytic lactones
    
    • Ivermectin
    • Moxidectin

Question 8

What is a major difference between Toxocara canis and Toxascaris leonina?

Answer 8

Toxocara canis has an extensive migration (hepatic tracheal)

When Toxascaris leonina larvae hatch in the small intestine and do not undergo a migration

Question 9

Describe the life cycle of Toxocara canis

Answer 9

• If larvae fail to break through the alveolus it will encyst in somatic tissue
• Direction taken at the alveolus is crucial in determining whether the larvae will undergo hepatic tracheal migration and develop to sexual maturity or somatic migration and remain as encysted L3
• Tracheal migration more common in puppies <1 month
• Ingestion of paratenic host results in alimentary development without migration
• Transplacental migration of larvae is the most important route of infection during the last trimester of pregnancy
  
  • Arrested larvae are reactivated in the bitch
  • After parturition, small numbers of larvae are found in the milk

Question 10

Describe the treatment of Toxocara canis:

Puppies < 2 weeks?

6 weeks or greater?

>3 weeks and 3 lbs?

Answer 10

• Puppies < 2 weeks
  
  • Pyrantel pamoate
  • Should start at 2 weeks of age and repeated every 2 weeks until 3 months of age
• 6 weeks
  
  • Piperazine
• >3 weeks and > 2 lbs
  
  • Drontal Plus (Prazi, pyranel, febantel)

Question 11

Describe the life cycle of Toxocara cati

Answer 11

• No transplacental transmission
• Tracheal migration is common no matter the route –> less likely to form somatic stages
• Transmammary infection is most important route for kitten
• Paratenic hosts are most important for hunters

Question 12

What is the treatment for Toxocara cati?

Answer 12

Pyrantel (drontal)= 2 week old or greater

Question 13

What is the ascarid of cattle and buffalo in the developing world, including North Dakota?

Cattle and buffalo in developing world

Calves infected transmammary

Larvae are 0.75-1.5 mm in length

When a cow ingested embryonated egg, the larvae undergo hepatic tracheal migration before they make their way to the cows tissue where they live for up to 5 months

Answer 13

Toxocara vitulorum

Question 14

Ascarid of raccoon?

Answer 14

Baylisascaris procyonis

Question 15

Ascarid of skunks?

Answer 15

Baylisascaris columnaris

Question 16

What is the ascarid of bears?

Answer 16

Baylisascaris tranfuga

Question 17

What is the ascarid of woodchuck?

Answer 17

Baylisascaeis laevis