Parasitology - Lecture 5 Flashcards
What are the general features of Order Ascaridida?
- big (up to 50cm), white/ opaque, stout bodies
- most have 3 lips around mouth
- Posterior M is usually curved with 2 spicules
- very prolific
- eggs have thick shell (high survival rate),usually one cell inside
- larvae reach L3 within egg
- location: normally SI
What Ascarids infect pigs?
Ascaris suum
What Ascarids infect horses?
Parascaris equorum
What Ascarids infect cattle?
Toxocara (Neoscaris) vitulorum
What Ascarids infect dogs?
Toxocara canis
Toxascaris leonina
What Ascarids infect cats?
Toxocara cati
Toxascaris leonina
What are the general features of Ascaris suum?
- dont seem to mature in ruminants, rabits,humans, etc. but will infect them
- most common GIT worm in pigs
- high prevalence in pigs younger than 6 months
- physically identical to Ascaris lumbricoides (the humn ascarid)
Where does Ascaris suum locate in the host?
- Adult: SI, but can be found in stomach, bile ducts and pancreatic ducts in heavy infections
- Larvae: migrate to liver, heart lungs, coughed up, small intestine.
What is the significance of Ascaris suum to humans?
can infect and mature in humans, possibly cause VLM
What is the morphology of Ascaris suum?
- size: up to 45cm,
- body: stout, pinkish yellow
- posterior (M): conical, bent, 2 equal spicules
- F vulva is anterior to middle of body
- eggs: brown-yellow. thick, mammilated shell. contains one cell
Describe the lifecycle of Ascaris suum?
- 200,000 eggs/ day
- eggs very resistant to stress
- 30-33C to develop
- L3 forms inside egg
- L3 containing eggs ingested by host, hatch in intestine and burrow into wall
- reach liver within 24 hrs. reach heart and lungs via blood
- coughed up and swallowed and mature in intestines,
PPT = 60 days
What species and where does Parascaris equorum infect?
- adults: SI of horse
- Larvae: migrate through liver, heart, lungs and back to SI
Describe the morphology of Parascaris equorum
- size: up to 50cm
- body: whitish, stout worms
- anterior: 3 lips around mouth, large anterior end
- eggs: brownish, thick-rough shell, 1-2 cells inside
What is the lifecycle of Parascaris equorum?
same as Ascaris suum
PPT= 80 days
What species and where does Toxocara vitulorum locate?
adults in SI of calves
what is the morphology of Toxocara vitulorum?
size: 15-40cm
anterior: 3 lips, cervical alae present but reduced. \
eggs: thick shelled, finely pitted outer coat, 1 cell inside
describe the lifecycle of Toxocara vitulorum
- eggs passed in poop
- host ingests embryonated eggs, but dont develop patent infection.
- larvae hatch, migrate to liver, lungs, muscles, brain, etc and arrest
- migrate to mammary glands during partuition and pass to calf.
- develop in SI of calf with no migration
- calves shed eggs in poop
What is the human significance of Toxocara canis?
zoonotic potential. can cause VLM and OLM and other syndromes
what is the morphology of Toxocara canis?
size: 10-18cm
anterior: 3 lips, cervical alae present and end gradually posteriorly
Posterior: til of M has caudal alae and terminal digitiform appendage. subequal spicules
eggs: subspherical, thick shelled, finely pitted outer coat, dark brown, contain 1 cell
What is the lifecycle of Toxocara canis?
- F are prolific
- 25-30C best temp
- L3 develop in egg
- infect by ingestion of eggs, hatch in duodenum and undergo either tracheal or somatic migration (and arrest)
- hypobiotic larvae are reactivated during pregnancy and infect puppies through milk or via placenta or infect SI of female.
- may also arrest in paratenic hosts
What factors affect whether a parasite undergoes somatic or tracheal migration?
- age
- immunity
- sex
- size of infective dose
Where does Toxocara cati infect?
small intestine
What is the significance of Toxocara cati on human health?
can infect humans and cause VLM and OLM
what is the morphology of Toxocara cati?
size: 3-10cm
anterior: 3 lips, large cervical alae that end abruptly (looks like arrow)
eggs: dark brown, thick, pitted, 1 cell in egg
