SHAFAQNA – The Grand Ayatollah Makarem Shirazi answered a question about keeping dogs.
The Grand Ayatollah Makarem’s: Dogs can be used for the purpose of guarding houses, herds, for hunting, and policing. But because it (dog) is a contaminated creature, and it is possible that it transfers various illnesses to the human being, keeping (playing with) dogs according to ways seen in the West (western countries) is prevented in Islam. At the same time, Islam does not allow even the stray dogs to be harmed, unless they are a danger (to the public). Feeding dogs is also a good deed.
Source: PERSIAN SHAFAQNA