food for rats to continue breeding and infesting more neighborhoods. The World Health Organization uses the latter definition, noting that rats and their fleas were a major factor in the spread of bubonic plague. By definition, the problem lies in the behavior of building. owners, which be changed with such disincentives as fines and regulation enforcement. Given the immediacy of the problem, the preferred choice among many groups is one of extermination for public safety. that is, the preference is to Poison and kill the existing rats that bite and cause disease. The two definitions of the problem, as in the case of other well-structured problems such as stray dogs, lead in different implementation directions.