It is common these days to see bowls of water for dogs outside of shops or coffee houses. Fountains in parks are also commonly used for our dogs when they are out and about. There has been some concern lately regarding the safety of dogs drinking out of communal bowls or fountains.
However, there are actually very few communicable diseases that are spread directly by mouth.
Contagious diseases in dogs are more commonly spread in other ways. Many intestinal pathogens (such as parvovirus and roundworms) are spread through fecal-to-oral transmission. These organisms won’t spread in a communal water bowl unless there is fecal contamination in the bowl.
Many other infectious diseases are spread through the respiratory tract. For instance, the pathogens that cause kennel cough and canine influenza are passed during coughing or sneezing. But if an infected dog sneezes on or near the bowl, there is the potential for other dogs to be exposed to these respiratory pathogens. The canine papilloma virus (which causes a minor, self-limiting syndrome in dogs) can spread through saliva.
If your dog has a healthy immune system it is not likely that he will contract a serious disease from a shared water bowl.