2. Definition of Parasite
• A parasite is an organism that lives on or in a host and gets its food
from or at the expense of its host.
• The parasite cannot live, grow or multiply without a host.
• It rarely kills the host but some types are fatal
3. Diagnosis
• Patient symptoms
• Geographical info
• Past travels
• Obtaining proper sample
• Some parasites like Ascaris cause
symptoms before eggs are
present in stool samples
5. Types of Parasites
• Protozoa :Protozoan parasites
have only one cell can multiply
inside the human body.
• The most common intestinal
protozoan parasites are for
example Giardia lamblia,
Entamoeba histolytica
• Diagnosis is made by observing
trophozoites or cysts
6. Types of Parasites
• Helminths: Helminths are worms with
many cells. Nematodes
(roundworms), cestodes (tapeworms),
and trematodes (flatworms) are
among the most common helminths
that inhabit the human gut. Usually,
helminths cannot multiply in the
human body
• Most commonly encountered are for
example Ascaris lumbricoides
(roundworm), Taenia saginata or
solium (tapeworm), Trichuris trichiura
(whipworm)
• Diagnosis is made by observing eggs
or larvae
8. Blood Examination
• Thin films:
• Blood is spread over the whole slide like
in hematology
• RBC’s are intact after staining
• Thick films:
• Blood is concentrated over a small area
• RBC’s are lysed during staining
• Only WBC nuclei, platelets and parasites
(if present) are visible
• Best sample is a finger prick
• You should be able to see letters behind
the film or it is too thick and will peel off
• Allow to dry overnight and stain with
Giemsa
• This is preferred over the thin film
because it is more concentrated
9. Fecal Specimens
• Sample collection
• Samples should be properly labelled
• Fresh sample is needed. Old or poorly preserved samples are unacceptable
• Samples should be free of urine and not contaminated with toilet water or
soil
• Samples should be collected directly in urine cups
• Obtain 3 samples day in day out
• Trophozoites degenerate overtime
11. Fecal Specimens
• Prepare a wet mount
• Dip a wooden stick into various parts
of the feces
• Put a drop of saline on a slide
• Mix the stool on the wooden stick
with the saline drop
• Put a cover slide
• Make sure there are no air bubbles
• 2 mounts are made
• Stain one mount with iodine
• Iodine makes nuclear structure of
protozoan parasites more evident
• Examine at 10x objective
• Move to 40x
12. Cellulose tape for Pinworms
• Enterobius vermicularis eggs are deposited in the perianal area.
Pinworms are especially active at night or early morning.
