Detection of Parasitic Infections by Fecal Examination
The commonly occuring intestinal parasitic infections of cats, dogs, and other animals including
people are efficiently detected by microscopic examination of fecal samples. In our laboratory at
the University of Tennessee College of Veterinary Medicine parasitic infections in companion
animals and domestic livestock are detected by fecal examination. The use of these methods is
determined by (1) the parasitic species we hope to identify in the sample and (2) the host species
from which the fecal sample originated. In this document we provide a discussion and review of
our fecal examination methods. It is our hope that this information will encourage wide-spread
adoption of the best practices for detecting parasitic infections in client-owned animals.
Fecal Direct Smear
This technique is used to detect motile parasite stages such as protozoan trophozoites and
helminth larvae frequently passed in the semi-formed and loose to fluid feces of animals. The
larvae of Strongyloides stercoralis are usually associated with diarrhea in young puppies and
have zoonotic potential. The trophozoite stages of Giardia and several Trichomonad species can
be found in the loose stools of many different host species. Giardia is generally considered to be
a zoonotic parasite and play a causative role in diarrheal disease, however, the clinical
significance of the Trichomonad parasites is quite variable depending on it pathogenicity for
particular host species. Flotation concentration procedures have the potential to distort the
delicate structures of these organisms and obliterate their diagnostic attributes so that accurate
identification is impossible. Trophozoites and larvae may be immobilized by dropwise
application of dilute Lugol’s iodine solution (10.5%) to facilitate microscopic examination of
their diagnostic morphology.