This is a test that is most often performed in farm animals. The purpose is to measure the worm burden prior to administering a deworming agent and then again following the deworming agent. This allows the tester to monitor the efficacy of the deworming agent that was used. We are also able to identify those animals (usually 10%) that are the high shedders within a herd. Most farm animals will carry a worm burden all of the time due to the presence of worms in their environment, but some carry a larger burden than others. Pastured animals often pick up immature parasite forms from the pasture itself.
A Fecal Egg Reduction test is actually a series of two tests, performed about 6 weeks apart. A fecal sample is obtained. That sample is tested using a three stage process. First 5 grams of the fecal sample is placed into a special test solution and "mixed up." After being mixed, the sample and solution are strained. The strained sample is then placed in a centrifuge for 10 minutes, where it is spun at a high rate. Once the spinning is concluded, a cover slip is place on top of the sample. This allows the eggs to float to the top of the solution and "stick" to the cover slip. After 10 minutes, the sample is viewed through a microscope and an egg count is performed.