All dogs are susceptible to certain kinds of parasites, worms being one of the most common ones you’ll run into. Two worms that commonly set up shop in dogs are the tapeworm and the roundworm.

The tapeworm can affect dogs of any age, but they’re a little more common in older dogs. There are a few types that show up in dogs, some of which are actually transmitted from sheep. But the most common kind comes from your dog’s fleas. The whole thing starts when your dog tries to kill an annoying, itchy flea by eating it. The flea, in turn, carries tapeworm eggs in its stomach, eggs that have been waiting the whole time for just this moment. The only way to rid your dog of tapeworms over the long term is to totally clear his environment of fleas. Tapeworm in your dog is something to take seriously. It can even transmit itself to humans, especially if you have young children who might swallow an infected flea.

It’s easy to tell if your dog has tapeworms. Owners often see segments of the worm in the dog’s feces that look like grains of rice. Your dog will probably also clue you in to his problem by licking or chewing the anal region, and scooting along the ground.

Fortunately, for the short-term, it’s simple to control this type of parasite. A safe drug known as Praziquantel is commonly used to kill tapeworm, and recently it was even made available over-the-counter. Just look for “tapeworm tabs” at your local pet store or favorite online retailer.

Roundworm is another common parasite that mostly shows up in puppies. The pups usually transmit roundworm from one to another through fecal contamination, which is extremely hard to avoid. What’s worse, more than a few puppies are born already infected with roundworm, which they received through the mother’s uterus. Roundworms that spent years lying latent in the mother’s tissues are often activated by her pregnancy. They then circulate through her bloodstream, passing themselves on to the unborn puppies.

It’s possible to control this problem by using a safe anthelmintic early on in mom’s pregnancy to destroy the worm load. Or, breeders can treat the litter at about four weeks of age, and then repeat the treatment before the puppies leave for their new homes. Once the puppy comes into your care, he should still be treated regularly — every three to four weeks until he’s six months old.

Dogs often build up quite an immunity to roundworm as they get older, and don’t usually require treatment after they reach six months of age. But you’ll still want to keep an eye on this parasitic problem, because it’s not easy to find roundworm with the naked eye.