Unfortunately, humans can be infected by Toxocara roundworms. Most often children are infected by playing in contaminated soil and accidentally ingesting previously digested worm eggs. Gross! Although rare, the worms can then cause eye, lung and neurological signs as they migrate through the body.
Luckily, regular deworming of pets minimises this risk. Keep children away from areas where pets go to the loo. Sandpits are best covered to prevent cats from using them as litter boxes. If this does happen, remove the poop promptly and wash your hands thoroughly.
In the UK, tapeworm species usually cause few symptoms and are easily treated. European species can cause serious, life-threatening problems.