Fecal Baermann

By Kristiina Ruotsalo, DVM, DVSc, Dip ACVP & Margo S. Tant BSc, DVM, DVSc

What is a fecal Baermann test?

A fecal Baermann is a special test that detects certain types of parasites or "worms." Many parasites shed their eggs in the host's stool. Infection with these parasites can be diagnosed with a simple fecal flotation test in which the stool is examined microscopically for the presence of parasite eggs (see handout “Fecal Flotation”). However, some parasites pass free larvae (immature worms) instead of eggs in the stool. These larvae cannot be detected by routine fecal flotation, and a special technique called a fecal Baermann is needed to diagnose infection.

How does the test work?Picture of saline solution being poured into funnel

Stool material is placed in a special funnel-shaped collection device and covered with warm water. The sample is left to stand for 1-2 hours or longer. During this time, larvae actively move out of the stool material and sink to the bottom of the funnel where they are collected and identified.

What sample is needed?

Two to three teaspoons of fresh stool material (about the size of a golf ball) is all that is needed. Ideally, the stool sample should be collected as soon as it is passed and should be as free as possible of grass, gravel, kitty litter, etc. With larger dogs, your veterinarian may want to collect stool material directly from the pet’s rectum. If you collect the sample at home, your veterinarian may provide a container or you can use any clean, dry container with a tightly fitting lid, such as a jar or plastic tub. For best results, the stool material should be examined within 12-24 hours of being passed.

When should a fecal Baermann be performed?

A fecal Baermann should be performed whenever your veterinarian suspects infection with a parasite that passes larvae rather than eggs in the stool. The most common parasite diagnosed with a fecal Baermann is lungworm, which typically causes signs of coughing. The adult lungworm lives in the lung and releases larvae into the lung tissue. When the host coughs, the larvae are coughed up and swallowed and then passed out in the stool. A fecal Baermann is necessary to diagnose lungworm infection.

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