Practical 3: Helminths and Intestinal Protozoa Flashcards
What is the method of examination of protozoa?
It is through the ova and parasite examination
The ova and parasite examination consists of three components which are?
a) Direct wet mount
b) Concentration, which consists of both sedimentation and flotation
c) Permanent stained smears
What is the direct wet mount?
A direct smear, of unfixed faecal matter, this allows for one to observe the motility of the protozoan trophozoite
What are the reagents used in a direct wet mount?
0.85% Sodium chloride and Lugol’s iodine or D’Antoni iodine
For the Sodium chloride smear use?
It allows for a lot of eggs to be viewed
For the iodine solution?
It allows for a huge number of cysts morphological details
What is the concentration method?
It allows for the recovery of eggs, spores, cysts, larvae and oocysts, this occurs through two methods flotation and sedimentation
What are the principles of using sedimentation method?
It uses a solution with a lower specific gravity such as formalin-ethyl acetate, this allows for the eggs to settle, while the others things float at the top
What are the principles of using the floatation method?
Use of zinc sulphate or sheather’s sugar, of which they both have high specific gravity, thus causing the eggs to float and the other substances to settle.
What are the disadvantages of using the floatation method?
a) Eggs with a higher specific gravity are also going to settle
b) Can lead to damage of the egg structure, such as the egg wall therefore making it hard to identify
c) Not able to detect operculated eggs
What is the permanent stained smear?
It is a method of of identification of intestinal protozoa, under oil immersion.
What is the principle of a permanent stained smear?
It provides contrasting colours for the background and the parasite
What are the reagents used in a permanent stained smear?
a) Wheatley modification of the Gomori tissue trichome
b) Iron- hematoxylin
c) Polychrome IV
What are the disadvantages of using a permanent stain smear?
a) Difficulty in identifying the parasite due too much absorption of the stain
What is the acid-fast permanent stained smear?
It allows for identification of acid-fast characteristics of organisms such as oocysts of coccidian spp.
What are the examples of coccidian spp?
a) Cryptosporidium
b) Cystoisospora
c) Cyclospora
What reagents are used for the acid fast PSS?
a) Kinyoun’s acid fast stain
b) Ziehl-Neelsen stain
What are the limitations of using direct mount stain?
When iodine is used to for viewing of the organism, it kills the organism and motility will be lost
What are the types of preservatives or fixatives?
a) Merthiolate formalin
b) Sodium acetate-acetic acid formalin
c) Polyvinyl alcohol
d) Schaudinn’s fluid
