Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Fecal Examinations

Stephen L. Barten DVM, Vernon Hills Animal Hospital, Mundelein IL

An organism that lives in or on another larger organism is a parasite. The larger organism is the host. The damage caused by a parasite varies with the species of both parasite and host, the numbers of parasites and the relative health and state of nutrition of the host. Any parasite found in captive reptiles should be considered abnormal and an effort made to eradicate them.

Parasites may be external or internal with respect to the host. External parasites are usually diagnosed by observation. These include mites and ticks. Internal parasites are more common than external parasites but are more difficult to diagnose. A successful internal parasite will stay inside the host; those that pass out in the feces dry up and die. The parasites are rarely found in the feces with the naked eye. However, internal parasites produce microscopic eggs or cysts which do pass out in the feces to contaminate the environment and infest other hosts, thus insuring new generations of parasite.

A fecal examination for parasites should be done routinely for newly acquired reptiles and is especially important for wild caught reptiles. First, the specimen that is submitted should be feces rather than something else. Most reptiles produce urinary waste in the form of uric acid, which is white to yellow in color and solid in consistency. It may be powdery or it may be formed into balls. Uric acid waste may be passed in conjunction with feces or by itself. By contrast, feces is brown to black and looks like, well, exactly what it is. It is common for reptile owners to mistakenly submit balls of uric acid to be checked for parasites. Likewise a poop sample from the water dish, which owners usually submit water and all (sometimes as much as a quart!), is virtually useless.

The second condition for a successful fecal examination is that the sample has to be fresh. The ideal situation is when the reptile passes a fecal sample at the veterinary office during an examination. The second best is for the owner to observe the stool being passed and to bring it to the veterinary clinic immediately. At the very least, the sample should be less than 24 hours old. It may be placed on a damp paper towel in a plastic margarine tub and refrigerated to prevent it from drying out prior to submission. When a fecal sample dries out, the ova within it dry out and become impossible to detect.

The most common fecal examination is the fecal flotation. This technique concentrates parasite ova and cysts to increase the chance of detecting them. Approximately one teaspoon of feces is mixed with some water in a paper cup. It is poured through a wire tea strainer into a second cup to remove the solid matter. A tongue depressor may be used to stir the feces and squeeze all the Fecal Exams: liquid out of the solid waste in the tea strainer. The resulting liquid is transferred from the second cup into a centrifuge tube for three minutes. Fats and pigments will be on top in the supernatant, which is poured off and discarded. Any parasite ova remain in the sediment in the bottom of the centrifuge tube. A concentrated solution of salt (sodium nitrate, specific gravity 1.20) or sugar (sucrose, specific gravity 1.33) is added, the sediment stirred and the tube is stoppered and inverted several times. The tub is then centrifuged for five more minutes. Parasite ova and cysts float to the surface of the concentrated salt or sugar solution. The surface layer containing ova and cysts may be transferred to a microscopic slide using a glass or plastic rod. If simple gravity is used rather than centrifugation, a sample should be allowed to sit for 10-20 minutes before collecting the surface layer. Samples should be examined soon after slides are made, as crystals form as the media evaporates, obscuring any ova.

A third method for examining feces is the Baermann technique, which is a sedimentation technique. The method is used to check for nematode larvae, which swim poorly and sink to the bottom when suspended in water. One to three teaspoons of fecal matter is placed in a tea strainer over a glass funnel held on a laboratory stand. A short length of rubber tube held closed with a clamp is attached to the bottom of the funnel. The funnel is filled with lukewarm water and allowed to stand for several hours or over night. Nematode larvae come to the surface of the feces in warm water and fall off, sinking to the bottom of the apparatus.

A negative finding on a fecal examination means only that no parasites were detected in the sample submitted, not that the host is necessarily free of parasites. It is wise to obtain two or more negative fecal examinations before concluding that a patient is parasite-free.

An excellent beginner book on parasites is Roger Klingenberg's Understanding Reptile Parasites, 1992, Advanced Vivarium Systems, Lakeside CA.