Goat Fecal Float Tests – How and Why
The dynamics of a common test for parasites in goats.
Reading Time: 5 minutes
What is the biggest health management challenge facing goat owners? Is it hoof care? Digestion issues? Mastitis?
Nope — it’s parasites.
In fact, parasites are the biggest health issue caprines face. Coccidian and worms kill more goats than all other illnesses combined. The barber’s pole stomach worm (Haemonchus contortus) is the biggest troublemaker in America. It sucks blood and causes severe blood loss, anemia, diarrhea, dehydration, and death.
The most popular diagnostic tool veterinarians use to check for parasites is the fecal float test, sometimes called the egg flotation or Fecalyzer test. As the name implies, a fecal float test is based on the differences in specific gravity between parasite eggs and solution. When parasites reproduce, the eggs pass out of the host animal via its feces into the general environment (where they may be ingested by another animal, thus continuing the worm’s life cycle). When examined through a microscope, it’s the parasite’s eggs (or sometimes the oocytes, which are tough egg-like structures of fertilized female protozoans) — but not the actual parasites themselves — that will be visible.
Vets ask for the freshest poop available; straight from the animal is ideal. Some parasite eggs can hatch in as little as an hour, so fecal pellets aged 30 minutes or less are best. In older samples, eggs will have already hatched and not be visible in the fecal float, giving a false negative result. If you can’t get to a vet or laboratory rapidly, then place the fecal sample in a well-sealed container and refrigerate it, which will slow the development and hatching of any eggs. (Do NOT freeze any fecal samples; this destroys the eggs.)
Not all internal parasites can be determined by the fecal float test. Parasites outside a goat’s gastrointestinal tract, biliary ducts, or lungs will not be detected. Additionally, parasites whose eggs are too heavy to float, who exist solely as swimming protozoans, who produce live young, or which are so fragile they’re destroyed by the flotation techniques will not be detected via floatation. Tapeworms, which shed whole segments into the feces, also don’t float (but are otherwise easy to spot because the segments are large).
Steps for a Float Test
Floats are performed using a “Fecalyzer” apparatus. This consists of an outer casing which contains a removable filtration basket. The feces are placed inside the outer casing, then the filtration basket is replaced, squashing the feces down. The apparatus is then half-filled with a solution of sodium nitrate, Sheather’s sugar solution, zinc sulfate solution, sodium chloride solution, or potassium iodide. Once the liquid is in place, the filtration basket is rotated vigorously, which breaks up the fecal material into fine particles that become suspended in the solution. Parasite eggs float upward, and the heavier fecal matter remains behind at the bottom of the container.
After this step, the filtration basket is locked in place, and additional solution is carefully added to the container until it reaches the top — in fact, so far to the top that the liquid actually bulges above the lip, forming a small dome called a meniscus. A glass microscope coverslip is gently placed on top of the meniscus and left in place between 10 and 20 minutes (depending on the type of solution used).
The reason for the lag time is because parasite eggs take a bit of time to drift upward to the surface of the solution. The eggs collect at the surface of the fluid layer adjacent to the microscope coverslip, which then get picked up, along with a thin layer of fluid, when the coverslip is removed. Then the coverslip is placed, wet side down, onto a microscope slide, which sandwiches the fecal floatation fluid (and any parasite eggs) between glass. At that point, the microscope work begins as the vet examines the results to detect parasite eggs.
Float Test Problems
Fecal float tests are not perfect and can give both false-positive and false-negative results.
False-positive results can happen in a number of ways:
- Parasites are present but not causing health issues, and/or the animal’s immune system has them under control.
- The animal has clinical parasitism due to an underlying immune disorder (an animal is ill for another reason, so parasites flourish; but the parasites themselves are not causing the illness).
- The parasite species found in fecal flotation is not the right species for that host (the animal may have ingested a parasite that can harm another species but is not a concern for goats).
- Some species of parasites are incidental and simply not pathological (not all parasites are dangerous).
- Incorrectly diagnosing the correct parasite species (at a microscopic level, many parasite eggs look similar, so it’s easy to mistake harmless eggs for dangerous eggs).
- Lab error and veterinarian inexperience (enough said).
False negatives can happen because:
- The fecal sample isn’t fresh enough (the eggs have already hatched).
- The sample may be devoid of eggs (parasites don’t shed eggs nonstop, so a particular fecal sample may not have any eggs; alternately, some parasites shed comparatively few eggs).
- Low parasite burden (not every egg will be captured on the microscope slipcover).
- Delicate parasite eggs might be destroyed by the fecal float solution.
- Some parasite eggs do not float well.
- Some parasite eggs hatch early, making detection difficult with a float test.
- Some parasites produce health problems in an animal before they produce eggs.
- Incorrectly diagnosing the correct parasite species (mistaking benign parasite eggs for dangerous eggs).
- Lab error and veterinarian inexperience (enough said).
Some enterprising goat owners, particularly those comfortable with using a microscope and following laboratory procedures, perform their own fecal float tests. The correct equipment (a microscope, float solution, test tubes or test apparatus) can be obtained from veterinarian supply sources.
Fair warning: While the procedure to conduct a fecal float test and properly prepare slides is straightforward and can be learned with a little practice, the difficult part comes at the microscope stage. At this point, discerning the difference between benign and pathological results is easy to goof up, resulting in misdiagnoses.
If you can work under the tutelage of a veterinarian or laboratory specialist to learn what to look for on the slides under magnification and are willing to take the time and careful preps necessary for proper samples, then DIY testing is a fine option. The price of a fecal float test can range from $15 to $40, so if you are monitoring a large herd, conducting your own fecal float tests is a more cost-effective route.
Don’t Ignore Problems
For parasite management, the best offense is a strong defense. Caprine parasites are NOT a case of “If I ignore it, it’ll go away.” These little buggers don’t go away, and you don’t want to risk your goat’s health under the disillusion of “It can’t happen to me (or my goats).”
Parasite infestation can become deadly quickly. Don’t wait for your goats to experience problems; prevent them in the first place by scheduling routine monthly examinations of your goat’s feces. For a list of laboratories that conduct tests, check with your veterinarian or see this link: https://www.wormx.info/feclabs.
Do your beloved animals a favor and stay on top of their health.
Originally published in the Goat Journal 2020 special subscriber issue — Goat Health, From Head to Hoof — and regularly vetted for accuracy.