Most types of roundworm and hookworm can be acquired from soil contaminated by the faeces of an infected animal. Roundworm eggs, in particular, are great survivors, lying dormant in the soil for a year or more, until a cat picks them up on paws or muzzle, and swallows them while grooming.
Incidentally, most people are aware of the dangers to children from Toxocara canis, the dog roundworm, but there is growing evidence that Toxoxara cati, the cat roundworm, may pose a similar threat.
Hookworms employ a slightly different soil-based strategy. Their eggs hatch in the soil, and the larvae then burrow through the skin (usually on the feet) to get into the host’s bloodstream.
They can infect humans in the same way, and children are obviously at the greatest risk.