Why was a worm exam negative when actual worm was included in stool sample?

Question

3 days ago, my 2 1/2 month golden retriever started passing worm segments in her stool. It was one segment on the first and second days and two segments in the third day.

I'm pretty sure it is tapeworm, based on description and images/videos found online. (They look exactly like this.)

Called the vet's office, then took a stool sample. Made sure one of the flat-squirmish worms were in there. Later they called saying that the result was negative.

The sample was in a large Ziploc bag (I didn't have a small one at the time). I'm suspecting they analyzed the stool sample but weren't careful enough to look around inside the bag for the worm segment.

Why was a worm exam negative when actual worm was included in stool sample?

Should I call another vet's office for a second opinion, since the puppy continues to pass these?

Answer 1

I would get a second opinion.

The steps normally taken to do a fecal exam are as followed:

1) Macroscopic exam of feces - look at color, consistency, any mucous present etc.

2) Microscopic exam:

• Direct fecal smear - taking a small stool sample and directly smear it on a microscope slide

• Centrifuge Fecal flotation - mix fecal matter with a dense solution to allow potential eggs to float to the top, this solution is spun in a centrifuge to make all of the debris sink to the bottom. Once completed you top up the tube with solution and add a cover slip on top of the tube. You wait about 20 minutes before placing the cover slip on a microscope slide, waiting allows the eggs to float to the top. In the video I have added they do this a bit differently, we didn't have a centrifuge that would keep a cover slip in place.

• Fecalyzer fecal flotation - This is a more simple way to make eggs float to the top, the concept is the same as the centrifuge fecal flotation though instead you use a fecalyzer.

• Giardia snap test - this test detects their cyst antigen.

  It's very possible they could have missed it if there were no eggs present in the sample they took. Tapeworms release segments of their bodies that contain eggs, if these segment were in tact and no eggs released it could give a false negative. Your vet should be able to tell you what it is once you show him the physical worm and treat accordingly.