This article appears in November Family magazine.

While a person might turn his nose up at drinking a glass of water that’s been left on the kitchen counter for a couple of days, a dog or cat probably wouldn’t have the same reaction. However, pet owners should consider how often they clean their pets’ water bowls because a new study finds that potentially lethal bacteria may be lurking there.

The study from Hartpury University in the United Kingdom found that bacteria — which can be transferred from pets to their owners — can build up on plastic and ceramic pet dishes.

“Water and food bowls are dishes that just like our plates should be cleaned regularly. Nobody wants to use the same cereal bowl every day without washing,” said Dr. Bryce Kibbel, clinical assistant professor in the College of Veterinary Medicine at Iowa State University.

It’s not news that a dog’s water bowl may be filled with germs. A 2012 University of Calcutta study titled “Are We Aware of Microbial Hotspots in Our Household?” identified it as the third most-contaminated item within the household.

“Any surface that can collect biofilm (a collection of bacteria that can produce their own matrix to stick to each other and surfaces) can collect and harbor bacteria. Let’s just say, I don’t let my 8-month-old toddler play in the dog’s water bowl,” Kibbel said.

Harmful to humans

The study results were surprising, though, because it found that the bacteria could pose a risk for human health.

“We had hypothesised that the plastic bowl would contain the highest number of bacteria and stainless steel would contain the lowest numbers of bacteria, but we were surprised to find that ceramic contained the most harmful bacteria including salmonella, E. coli and MRSA,” said Aisling Carroll, animal science lecturer at Hartpury University.

This is the first study of its kind, so people may not be aware of the types of bacteria that may build up in their pets’ water bowls and that they can be transferred to humans and areas where the water bowl is kept or handled, Carroll said.

“There is also the possibility of cross-contamination from human to pet,” which this study did not focus on but will require further investigation, Carroll said.

Healthy tips

If your pet is drinking from a plastic or ceramic bowl, it may be time to switch it out for stainless steel, which the study found was the preferred bowl material to use to limit the number of bacteria that can grow on water bowl surfaces.

“Pet owners should ideally clean with hot water and a pet-safe disinfectant regularly,” Carroll said.

Water should be changed daily, and the more often bowls can be cleaned, the better, Kibbel said.

“Currently my recommendation is at least weekly for water bowls,” he said.

Scrub the bowls with dish soap and rinse with hot water.

“It would be best not to use the same sponge used on human dishes to prevent transfer,” Kibbel said. Or, use the dishwasher, which can attain a water temperature much higher than out of the faucet and be more effective at removal and killing of bacteria, he said.