Direct Fecal Smear Examination
Direct Smear Fecal Exam
1. Place a small amount of feces on a microscope slide.
2. Add a drop of liquid to the feces and mix thoroughly. The type of liquid added depends on what you hope to accomplish with the technique. If you are examining a liquid fecal sample for the presence of protozoan trophozoites (live active protozoa) then use saline (if any extra liquid is needed). If you are looking for helminth eggs and protozoan cysts in a small sample (bird droppings, rectal smear, etc) then either water or iodine may be used.
3. Cover with a cover slip. Move the cover slip around until it lays flat. You should be able to read through the smear (light from the microscope must be able to pass through the sample in order for you to examine it).
4. Examine the slide using the 10X objective, and then go over it with the 40X objective.
Because this technique examines only a very small amount of feces, it should only be used in the following circumstances:
a. Liquid feces where protozoan trophozoites may be present.
b. Fecal samples where the amount of feces obtained is too small to handle with any other technique.
c. As an adjunct to a flotation technique where you are looking for eggs that do not float. (In this case you probably would be better off running an ethyl acetate sedimentation and examining the resultant pellet using the direct smear method.)
Note: Circumstances "b" and "c" occur frequently when dealing with small fish, birds, amphibians and reptiles and thus the direct smear has some utility in dealing with fecal samples from these animals.
