The results also indicate that the threat rats pose to the health of poultry and humans has been underestimated.

Researchers studied the faeces of rats caught at an Abbotsford, BC poultry farm, and discovered they all carried avian pathogenic E. coli, a bacteria with the ability to cause disease in chickens and potentially humans.

More than one quarter of the rats were carrying multidrug resistant strains of the bacteria. The findings support lead author Chelsea Himsworth's theory that rats act as a "pathogen sponge," soaking up bacteria from their environment.

"If rats can absorb pathogenic E. coli, then they could potentially be a source of all sorts of other pathogens that we have not anticipated," said Ms Himsworth, assistant professor in the UBC School of Population and Public Health and leader of the Vancouver Rat Project, a group aiming to address the knowledge gap about the health threats associated with rats.

Ms Himsworth was surprised to find that the E. coli strains carried by the farm rats were very similar to those found in chickens, and totally different from E. coli strains found in urban rats.

"Basically, the rural rat gut looked like the poultry gut, and nothing like the urban rat gut," she said.

This latest study follows previous research by Ms Himsworth that found human pathogens, including MRSA (methicillin-resistant Staphylococcus aureus) and C. difficile, in the faeces of rats in Vancouver's Downtown Eastside.

"Rat infestations ought to be taken seriously," said Ms Himsworth.

"They need to be tackled with an educated, informed approach in collaboration with scientists and pest control professionals. Eventually, we would like to see the development of municipal programs for managing rat infestations and rat-related issues in BC, similar to what is currently in place in US cities like New York."