Two widely used diagnostic tools—fecal flotation and fecal antigen testing—play important roles in parasite detection, but they're not created equal. Understanding their differences and how to apply them in clinical practice is key to delivering optimal veterinary care.

Why Routine Fecal Testing Matters in Veterinary Medicine

Routine fecal testing is more than just a checkbox for wellness exams; it's a vital diagnostic strategy to identify parasitic infections that often go unnoticed. According to the Companion Animal Parasite Council (CAPC), parasites such as roundworms, hookworms, whipworms, and Giardia continue to pose significant health risks to dogs, cats, and even humans. These parasites are not limited to stray or outdoor pets—household pets regularly test positive during routine screenings.

  Fecal floats are sunk. New study shows fecal antigen testing catches 2x more infections as flotation. Learn more.

The CAPC annual parasite prevalence maps show that intestinal parasites remain highly prevalent across North America. Even more concerning is a recent DOGPARCS study that found that 1 in 4 dogs tested positive for at least one intestinal parasite for at least one intestinal parasite. These data reinforces that parasite exposure and infection are common, even in animals without clinical signs.

Key Differences

While both fecal flotation and fecal antigen testing are common tools for parasite detection in veterinary medicine, they work via fundamentally different mechanisms and offer distinct advantages.

Fecal Centrifugal Flotation

Centrifugal flotation offers the ability to detect a broad spectrum of intestinal parasites. This test isolates and identifies parasite eggs (ova) by concentrating them using a flotation solution and then examining the sample microscopically.

Flotation is effective for detecting common parasites like:

• Roundworms (Toxocara spp.)

• Hookworms (Ancylostoma spp.)

• Whipworms (Trichuris spp.)

• Some protozoa (e.g., coccidia)

However, fecal flotation depends on the presence of eggs or oocysts in the sample, which is not guaranteed. Parasites shed eggs intermittently or not at all during the prepatent period. Additionally, technician expertise and sample quality can significantly affect test sensitivity.

Fecal Antigen Testing

Testing for fecal antigen represents a more sensitive, modern alternative. Rather than relying on egg shedding, this diagnostic method detects specific parasite proteins (antigens) of the most common and clinically relevant parasites in the feces, such as:

• Roundworm antigen
• Hookworm antigen
• Whipworm antigen
• Giardia antigen
• Cystoisospora antigen
• Dipylidium caninum antigen

By detecting antigen rather than eggs, this method can identify infections even in cases of low parasite burden, intermittent shedding, or during prepatent periods. According to CAPC, it has an increased level of parasite detection over centrifugal fecal flotation alone for the species of parasites currently detectable by these assays. It addresses key limitations of fecal flotation and has quickly become a preferred option in veterinary medicine.

Study Results: Fecal Antigen Testing Finds More Infections

A recent IDEXX multicenter study of close to 900,000 canine and feline fecal samples demonstrated that testing for fecal antigen alone detected up to two times more infections than fecal flotation alone. This study confirmed what many veterinarians have already suspected—parasites frequently go undetected if we rely solely on flotation.

The study found that:

• Testing for antigen consistently outperformed flotation across all major intestinal parasites.

• Many positive cases would have been missed without using this diagnostic method.

• Fecal antigen testing provided veterinarians with more accurate diagnostic data, leading to better patient outcomes.

This growing body of evidence has influenced updated recommendations from leading veterinary organizations.

CAPC Guideline Updates: Moving Away From Passive Flotation

CAPC recently updated its diagnostic recommendations, advising against the use of passive flotation due to its lower sensitivity compared to centrifugal flotation and testing for fecal antigen. CAPC continues to support the integration antigen testing into routine fecal diagnostic protocols.

These updated guidelines align with modern veterinary trends, where many practices now use antigen testing alone or in combination with flotation to ensure comprehensive parasite screening.

How Often Should Fecal Testing Be Performed?

Both CAPC and parasite experts recommend:

• Annual fecal testing for all dogs and cats as part of routine wellness care.

• More frequent fecal testing for puppies, kittens, newly acquired pets, or animals with gastrointestinal symptoms.

Incorporating testing fecal antigen ensures you're not missing subclinical or prepatent infections that could otherwise go unnoticed.

Diagnostic Options

1. Fecal antigen testing alone. Ideal for screening and detecting silent infections quickly and efficiently.

2. Fecal antigen testing and fecal flotation. Both tests can be combined, providing more comprehensive screening than either method alone. While fecal antigen testing can detect most infections, flotation alongside antigen offers the ability to visualize eggs and potentially discover other parasitic infections not included in antigen panels.

Quick Comparison

Feature	Fecal Flotation	Fecal Antigen Testing
Detects	Parasite eggs (ova)	Parasite proteins (antigens)
Limitations	Egg shedding variability, prepatent periods, technician-dependent	Detects the most common and clinically relevant parasites (roundworm, hookworm, whipworm, Giardia)
Strengths	Identifies eggs for morphological confirmation	Detects up to 2x more infections; effective even without egg shedding
Recommended Use	Combined with antigen testing and centrifugal method. Passive flotation is not recommended.	Alone or combined with flotation for optimal results

Optimizing Your Fecal Testing Protocol

Modern veterinary medicine increasingly favors fecal antigen testing for its superior sensitivity and ability to identify infections during prepatent periods. Incorporating this type of testing alone or in conjunction with flotation can give practitioners greater confidence in their parasite screening protocols.

By adapting your fecal testing strategy to reflect current evidence and CAPC recommendations, you can:

• Better detect infections

• Improve preventive care

• Better educate pet owners about parasite risks

Providing effective parasite detection isn't just about checking a box—it's about protecting animal and human health.

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