Most of the times we tend to ignore the presence of slugs and worms as they are no threat to us. However, there are a few worm species that can be dangerous to human.
Scientists have discovered the New Guinea flatworm which appears to be harmless but can be really lethal to humans and the eco-system. The worm was first noticed in Miami and later it made it to some residents in Cape Coral in Florida.
It can cause skin problems if you come in contact with them. They feed on rats and once it is done they spread parasites into the home which can result in giving you meningitis-causing diseases.
It could damage the oxygen-giving and fruit bearing plants due to its toxic mucous. Though, it is unlikely to appear in front of you, it is still better that you know something about it.