Topic 5: Parasitology

Question 1

When are direct faecal smears used?

Answer 1

Detect mobile parasite stages

Question 2

What can Lugol’s iodine solution do?

Answer 2

Immobilise trophozoites and larvae under microscopic examination

Question 3

How do you prepare a faecal smear slide?

Answer 3

Place a drop of water on a slide with an equal amount of faces to dilute the faeces and make a thinner solution

Slowly apply stain

Mix stain, faecas and water with an applicator stick and make a very thin smear on the slide

Question 4

What objective lens should be used?

Answer 4

10x for parasite eggs and larvae

40x for protozoa

Question 5

When and how is sedimation examination done?

Answer 5

To concetrate heavy or operculated eggs or lavae that are too dense to float in floatation solution

Faecal is mixed with saline, water or soap in water solution.
Centrifuged or allow to stand for 20mins to sediment parasites and debris

Question 6

What methods are most frquently used to recover parasite eggs and oocysts?

Answer 6

Flotation techniques that rely on the differences in the specific gravity of the eggs, facel debris and flotation solution.