Ascaridoidea - pigs

Question 1

What are some general features of Ascaris suum?

Answer 1

• Typical ascarid - direct life cycle (however a paratenic host can spread), L3 in egg is infective, migratory (hepato-tracheal), SI site of infection
• PPP 7-9 weeks
• Very large worms (40cm)
• Important in all types of pig production systems as the life cycle can be completed indoors as well as outdoors
• Eggs are extremely resistant

Question 2

What is the life cycle of Ascaris suum?

Answer 2

• Adults in SI release eggs
• Maturation to L3 in egg in environment
• Egg ingested and L3 released
• L3 to liver via portal system, then lungs via circulatory system (hepatic vein, post vena cava, heart, pulmonary artery)
• Through lungs / trachea and back to SI
• Maturation in SI to adult
• PPP 7-9 weeks
• Earthworm can be paratenic host

Question 3

Why is it important that the Ascaris suum egg remain in the environment for at least 4 weeks?

Answer 3

• Maturation to L3 must take place or the parasite is not infective.
• Dependent on temperature

Question 4

Clinical signs are usually mild with Ascaris suum, and the occasional transient pneumonia is less significant than other species causing this dz. However, there is one finding that is economically important with regard to this worm, what is it?

Answer 4

• Milk spot liver
• Fibrous repair of inflammatory reaction of migrating L3’s in the liver
• Leads to condemnations of livers which could be economically important

Question 5

How is diagnosis of Ascaris suum made?

Answer 5

• Clinical signs and history (reduced productivity - reduced weight gain, increased fattening time, occasionally obstructive jaundice)
• FEC (typical ascarid egg - thick pitted shell, round)
• Incidence of liver condemnations

Question 6

What age group does Ascaris suum mainly affect?

Answer 6

• Predominantly a disease of young pigs
• Strong acquired immunity