Unrestrained dogs living alone, in small groups or in large packs cause the spread of disease, inflict wounds on people, damage property, create a hazard on roads, make excessive noise.
Problem is worldwide, particularly in urban areas. Said to stand at 600 million in 2003, the dog population is expected to double within 10 years.
Diseases spread by stray dog populations include rabies, hydatid disease and, to a lesser extent, anthrax, pasteurellosis and leptospiroses. Human injuries inflicted by stray dogs include bites, which may lead to infection, fractures and sprains in old people and children and road accidents. In Peru, there are at least 80,000 attacks a year, and in Brazil there are hundreds of thousands. Most of the victims are children.
Stray dogs may damage property, particularly gardens, with their faeces; and litter the streets by overturning dustbins, which also increases the risk of disease and encourages rats. Domestic animals may be injured or killed by packs of stray dogs. Barking and howling causes a nuisance to the community. Origins of stray dog populations include lost dogs, abandoned dogs, dogs which are sheltered by people but not owned by them, dogs bred from stray dogs. The size of the stray dog population varies in accordance with the social and cultural characteristics of the human population, nature of the area, and season of the year. In the UK, some 90,000 strays dogs are destroyed each year.