The common roundworm found in dogs is a rare but potentially serious cause of human disease. The larval stages burrow through the gut wall and become embedded somewhere within the body and can cause serious damage if they end up, for example, in the eye. There are occasional reports of the victim, usually a child, being blinded in one eye. However, the type of roundworm normally found in cats is much less likely to cause problems in humans and most of the parasites found in cats are unable to survive at all in people. Apart from regularly worming your pets, there are a number of other measures which can stop worms being passed on from cat to cat - or from cat to people.
Fleas are more numerous during summer and autumn.
Make sure that they wash their hands after playing in a garden or other open areas which may be used as a toilet by cats. Remember the greatest risk of children being infected with worms is from other children not your cat.