From Academic Kids
A pest is an animal which has characteristics which people regard as injurious or unwanted. It is possible for an animal to be a pest in one setting but beneficial or domesticated in another (for example, European rabbits introduced to Australia caused ecological damage beyond the scale they inflicted in their natural habitat). An example of serious pests are those organisms which vector human disease, such as rats and fleas which carry the plague disease, or mosquitoes which vector malaria. Other pests compete for the human food supply or agricultural crops, such as coddling moth on apples, or boll weevil on cotton. See also the entries for biological pest control and pesticide.