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My dog had roundworms, but tested negative after treatment. Why?

Updated On September 23rd, 2025

Pet's info: Dog | Miniature Pinscher | Male | neutered | 5 years and 4 months old | 17.86 lbs

When we went to the vet I showed the vet a picture of my dogs stool and he said he had roundworm . The vet give my dog safe Guard, the same day and he give us a stoo samplel test . 5 days after we took his stool sample and mailed it . We got the results today that he tested negative for parasites. I don't believe that , iam so confused

2 Answers

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on March 16th, 2017

If you took a stool sample five days after Bronx was given the deworming treatment and then the sample showed no signs of worms, it likely means that the deworming treatment was effective and killed all the worms. The deworming treatment starts working within hours of administration to kill the worms present.

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    Answered By Lauren Jones VMD

    Veterinarian

    Published on

    I know it can be confusing, but this happens quite often. When we check stool samples for parasites, we are looking for the eggs that they shed. Parasites shed eggs intermittently, so it is quite possible that the roundworms found in Bronx's stool weren't shedding eggs when you collected his stool sample.

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