Every puppy and kitten is also dewormed several times throughout the vaccination process. Their first deworming should occur at two weeks of age. It is not uncommon for young pets to become seriously ill from these parasites.
Intestinal parasites, or worms, are passed from the mother and are even in the soil in some cases. Many intestinal parasites can cause problems for people too, so we deworm even if tests are negative. These tests are still important though.
The most common dewormers will not eliminate every type of worm and there are other common infestations, such as coccidia or giardia, that also require different medication.