Most types of roundworm and hookworm can be acquired from soil contaminated by the faeces of an infected animal – that’s why it’s so important to use a “poop-scoop” and dispose of your dog’s faeces responsibly.
Roundworm eggs, in particular, are great survivors, lying dormant in the soil for a year or more, until a dog picks them up on paws or muzzle, and swallows them while grooming. Of course, children can be infected with Toxocara canis in exactly the same way, and the migrating worm larvae can cause permanent eye damage in humans.
Hookworms employ a slightly different strategy. Their eggs hatch in the soil, and the microscopic larvae then burrow through the skin (usually on the paws) to get into a dog’s bloodstream.