I have noticed that most dog parks have “dog bowl” style drinking fountains. Is it safe to allow pets to drink after each other in a common bowl that is never cleaned or washed?
It may seem counterintuitive, but very few communicable diseases are spread by mouth. Water consumed from a communal bowl passes directly to the stomach. The stomach is very acidic and many germs cannot survive there.
Contagious diseases in dogs more commonly spread in other ways. Many intestinal pathogens (such as parvovirus and roundworms) spread through fecal-to-oral transmission. These pathogens are not present in the saliva, and therefore won’t spread in a communal water bowl unless an infected dog defecates in the bowl.
Many other infectious diseases spread through the respiratory tract. For instance, the pathogens that cause kennel cough and canine influenza are aerosolized during coughing or sneezing. When the pathogens are inhaled by a susceptible animal, they infect the respiratory system.
Of course, there are a few exceptions. The canine papilloma virus (which causes a minor, self limiting syndrome in dogs) can spread through saliva. And if a dog sneezes at the bowl, other dogs may be exposed to respiratory pathogens.
However, if your dog has a healthy immune system it is not likely that he will contract a serious disease from a shared water bowl.