Parasitology B Flashcards Preview

DVM2 UniMelb > Parasitology B > Flashcards

Flashcards in Parasitology B Deck (9)
Loading flashcards...
1

Order Ascaridida features

- 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

2

Ascarid general life cycle

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

3

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

Ascaris suum (zoonotic)
Ascaris lumbricoides

Small intestine

Direct +/- paratenic host

4

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

Parascaris quorum

Small intestine

Direct

5

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

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)

6

Ascarids of birds (species, site, life cycle)

Ascaridia
- Small intestine
- Direct + paratenic host

Heterakis
- Large intestine
- Direct + paratenic host

7

Ascarids of cetaceans (species, site, life cycle)

Anisakis
Contracaecum

Stomach, Small intestine

Indirect- copepod, fish (zoonotic potential)

8

Ascarid significance (adults, larvae, zoonotic potential)

- 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

9

Ascarid features important for control

- 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