Parasitology B

Question 1

Order Ascaridida features

Answer 1

• Large nematodes (5-15 cm; females larger)
• Adults feed on gut contents (usually SI), larval stages migratory
• 3 large lips
• Some have cervical alae (wings)
• Males have coiled tail
• Females prolific egg layers (200,000 / day)
• Thick egg shells- v resistant

Question 2

Ascarid general life cycle

Answer 2

Adults in small intestine

• -> unembryonated egg shed in feces
• -> embryonated egg (2-3 weeks)
  1. –> ingested by paratenic host species (visceral migration
• -> ingestion of paratenic host
• -> direct development in gut
  2. –> ingestion of L3 egg
• -> hepatopulmonary migration
• -> residence in SI

Question 3

Ascarids of pigs/humans (species, site, life cycle)

Answer 3

Ascaris suum (zoonotic)
Ascaris lumbricoides

Small intestine

Direct +/- paratenic host

Question 4

Ascarids of horses/donkeys (species, site, life cycle)

Answer 4

Parascaris quorum

Small intestine

Direct

Question 5

Ascarids of dogs/cats (species, PPP, site, life cycle)

Answer 5

Toxascaris leonina (+ foxes)- PPP = 7-10 weeks
Toxacara canis (+ cows; most common in dogs)- PPP ~ 5 weeks
Toxacara cati (+ cows; most common in cats)- PPP ~ 8 weeks
Baylisascaris spp. (dogs, raccoons)

Small intestine

Direct + paratenic host
+ transmammary (T. cati, T. canis) + transplacental (T. canis)

Question 6

Ascarids of birds (species, site, life cycle)

Answer 6

Ascaridia

• Small intestine
• Direct + paratenic host

Heterakis

• Large intestine
• Direct + paratenic host

Question 7

Ascarids of cetaceans (species, site, life cycle)

Answer 7

Anisakis
Contracaecum

Stomach, Small intestine

Indirect- copepod, fish (zoonotic potential)

Question 8

Ascarid significance (adults, larvae, zoonotic potential)

Answer 8

• Common, usually young hosts (<1 year)
  Adult worms:
• luminal feeders–>malnutrition, reduced weight gain, stunted growth
• diarrhea, colic, vomiting
• cholestasis, ileus, blockage, rupture–> peritonitis
  Larvae:
• hepatopulmonary migration (HPM)–> mechanical and inflammatory organ damage
• milk spots in pigs- organ condemnation
• pneumonia (asthma-like signs)- lung damage, secondary viral/bacterial pneumonia
  Zoonotic:
• A. scum cross-infect humans
• T. cati and T. canis larvae–>ocular and visceral larval migrans
• fish-borne anisakid larvae–> gastritis

Question 9

Ascarid features important for control

Answer 9

• eggs passed in feces need time to embryonate in soil
• eggs robust- can remain in soil for several years–> higher risk in extensive piggeries than intensive
• T. canis transplacental/transmammary transmission–> can present in pups younger than PPP