The fecal float test, also known as fecal flotation, is a common, non-invasive diagnostic procedure routinely performed in veterinary medicine. Its purpose is to detect the presence of microscopic eggs, larvae, or cysts of intestinal parasites within an animal’s stool sample. This foundational laboratory technique is inexpensive and simple to perform, making it a standard part of routine health screenings for pets. Identifying the reproductive stages of internal parasites allows veterinarians to diagnose infections and select the correct medication for treatment.
Why Veterinarians Rely on the Fecal Float
Veterinarians rely on the fecal float test as a primary tool for preventative healthcare, especially during routine wellness examinations and new pet visits. Many intestinal parasitic infections are asymptomatic, meaning the animal shows no outward signs of illness in the early stages. Screening healthy animals is necessary to catch infections before they progress and cause problems like diarrhea, vomiting, or weight loss. Regular testing is particularly important for young animals, such as puppies and kittens, because they are highly susceptible to infection.
This diagnostic tool also plays a significant role in public health by addressing the zoonotic potential of certain parasites. Some intestinal parasites found in pets can be transmitted to humans, causing illness, particularly in children or those with weakened immune systems. Detecting and treating these infections in animals helps to reduce the environmental contamination of parasite eggs, which limits the risk of transmission to the human population. Routine fecal testing helps veterinarians manage the overall parasite burden in the community.
How the Fecal Float Test Works
The scientific principle behind the fecal float test is specific gravity, which measures the density of a substance compared to water. Parasite eggs and cysts, the reproductive stages shed in the stool, have a lower specific gravity than most fecal debris found in the sample. Flotation solutions, such as zinc sulfate or concentrated sugar solution, are mixed to have a specific gravity higher than the parasite eggs but lower than the stool material.
When the fecal sample is mixed with this dense solution, the heavier debris sinks to the bottom of the container. The lighter parasite eggs and cysts become buoyant, floating up to the surface of the liquid. The standard procedure involves collecting a small stool sample, mixing it thoroughly with the flotation solution, and then straining the mixture to remove larger pieces of fecal matter. The liquid is then placed into a tube or vial, where a coverslip is placed on top of the meniscus, the curved surface of the liquid.
After a waiting period, typically 10 to 20 minutes, the parasite eggs that have floated to the surface adhere to the underside of the coverslip. The technician carefully lifts the coverslip and places it onto a glass slide for microscopic examination. Although passive flotation works, centrifugal flotation uses a centrifuge to apply a stronger force. This spins the sample to separate components more efficiently, resulting in a higher recovery rate and increased accuracy.
Common Parasites Identified
Microscopic examination of the coverslip allows the veterinarian to identify various intestinal parasites by the distinct shape and size of their eggs or cysts. The standard fecal flotation technique is effective at concentrating and identifying the eggs of common roundworms, which often appear as spherical, thick-shelled structures. It also reliably detects the oval-shaped eggs of hookworms and the characteristic football-shaped eggs of whipworms.
The test can also identify the oocysts, or reproductive stages, of certain single-celled organisms, such as Cystoisospora (a type of coccidia). However, the technique has limitations, as not all parasites are easily detected using standard flotation. Certain protozoan cysts, like Giardia, may not float well or can become distorted by the high-density flotation solutions, making them difficult to identify.
Other parasite stages, such as the heavier eggs of certain flukes or tapeworm segments, may sink with the fecal debris instead of floating. In these cases, the sample may require an alternative testing method, such as a fecal sedimentation or an antigen test, to confirm the infection. Once a positive result is confirmed, the specific identification of the parasite guides the veterinarian in prescribing the appropriate deworming medication.