[Mari-Lou]

Most worms won't be seen unless the dog has a large number. Worm eggs are microscopic so your vet needs to look at a stool sample under the microscope. There are roundworms, hookworms, tapeworms, whipworms, coccidia, and giardia.
Roundworms, hookworms and giardia can be transmitted to people. Puppies get roundworms from their mothers when drinking the milk, so most have them.
You need to take the puppy to a vet for a checkup with a stool sample and your vet can let you know if the older dog may need medicine. Stool samples should be checked at least 1 x a year and ideally 2 x a year all of a dogs or cats life.