Comparison of Fecal Examination Techniques
TECHNIQUE
ADVANTAGES
DISADVANTAGES
Direct Smear
- Quick to prepare.
- No distortion of parasites if isotonic saline is used as diluent.
- Only way to see live trophozoites (isotonic saline must be used as the diluent).
- Useful for examining feces of small birds and reptiles (where trematode eggs are common).
- Can miss parasite if concentration is too low or if too much debris or fat is present.
- Sand, seeds, or other fecal debris can make apposition of coverslip onto slide difficult.
- May take a long time to examine.
Saturated Sucrose or Salt
- Procedure floats the most common helminth ova and coccidian oocyst .
- Solutions are inexpensive.
- There is little debris to obscure the view of the parasite.
- Procedure will not float trematode ova and some tapeworm (pseudophyllidian) ova.
- Distorts Giardia cysts.
- Time consuming if centrifugation not performed.
- Unsuitable for fatty stool samples.
Zinc Sulfate Flotation
- Recommended procedure for most fecal exams
- Procedure floats most helminth eggs.
- Best method for protozoan cysts, especially Giardia.
- There is little debris to obscure view of parasites.
- Procedure will not float some trematode ova, and some tapeworm (pseudophyllidian) ova.
- Unsuitable for fatty stool samples.
- ZnSO4 is expensive and a hydrometer should be used to make up the solution.
Ethyl Acetate Sedimentation
- Procedure recovers ALL types of helminth ova, larvae, and most protozoan cysts.
- It is the best technique for formalin - fixed samples and for stools with high fat content.
- It is more difficult to perform than other techniques.
- Ethyl acetate is flammable and expensive.
- There is more debris in preparation preps than in flotation preps - therefore it will take longer to read.
