🔬 Parasites & Fecal Analysis · 7 min
Finding and interpreting parasites
Why this matters
A single negative fecal is the most commonly misread result in rehabilitation. Knowing why keeps you from missing a treatable cause of death.
By the end of this lesson you will be able to
- Describe fecal flotation and sedimentation and what each recovers
- Explain why repeated samples are required
- Manage ectoparasite loads appropriately
Two techniques
Fecal flotation suspends the sample in a solution so that lighter eggs (roundworms, hookworms, coccidia) float to the top. Sedimentation recovers heavier eggs, such as trematode (fluke) eggs, from the bottom. Both require a microscope. Examine all fecal samples fresh, and inspect visually for tapeworm segments before you prepare a slide.
One negative fecal rules out nothing
Many parasites shed eggs sporadically, so eggs are not present in every stool. An infected animal can produce a negative fecal. When internal parasites are suspected, run several samples over time. If a fecal is negative and the animal is still sick, that is a reason to test again, not a reason to stop looking.
Do not treat blindly
Wildlife cases should not automatically be treated for intestinal parasites on presentation. Many wild animals, particularly adults, carry some parasites normally. Do a fecal exam and evaluate the number and type before deciding. Intestinal parasites are a common cause of diarrhea, and if untreated can cause anemia and weight loss.
Ectoparasites
Healthy animals normally carry some external parasites: fleas, ticks, mites. Large loads become life threatening, causing hair loss, anemia and secondary bacterial infection. Bird feather lice (mallophagan lice) do not bite people or transmit disease to us, although they are thought to transmit several avian diseases.
Treat with care: flea powder made for dogs is too toxic for small mammals. Kitten flea powder or spray, with lower pyrethrin concentration, is preferred, and avian mite spray is less toxic still.
Mange
Mange is caused by skin-burrowing mites: Sarcoptes scabiei and Notoedres centrifera are the two most common in wildlife. Red foxes, coyotes and porcupines get severe sarcoptic mange; notoedric mange is most common in squirrels. It is transferred readily among social mammals and is best treated with ivermectin or a similar drug, after a skin scrape identifies the parasite.
Baylisascaris again
The raccoon roundworm cannot complete its lifecycle outside the raccoon, so only raccoons shed eggs in their feces. But the eggs deposited outdoors remain viable up to ten years, resist scrubbing and ordinary disinfectants, and are killed only by flaming with a blowtorch. In non-raccoon hosts, including people, the larvae migrate and cause central nervous system damage, blindness and death.
From the field
Two baby opossums arrive with large areas of hair loss and crusting on the stomach and hind legs. You already have several opossums you are hand-feeding. What do you do? Isolate the new arrivals, feed them last, handle them with care because the condition may be contagious to you as well as to other opossums, and contact your cooperating veterinarian for the diagnostic tests that separate ringworm, sarcoptic mange and allergic skin disease.
This lesson is part of the NY Wildlife Rehabilitator Exam course. Open it in the course to answer the retrieval checks that go with it, track what you have read, and quiz the whole unit. Lessons, quizzes and the glossary are free.