They give you joy. They give you loyalty. They give you sloppy kisses.

But before you allow Fido or Fluffy to climb into bed with you at night, as an increasing number of Americans are doing, know that they can also give you something else: zoonoses.

A UC Davis veterinary professor has penned an article for a scientific journal showing that people who allow their pets to lick them, give them "kisses" or sleep with them are at risk for a variety of diseases known as zoonoses. The conditions can range from the mundane to the life threatening.

Bruno Chomel and his co-author, Ben Sun, emphasize that pets provide many health benefits, including stress relief, and they stop short of recommending that people abstain from smooching their pooches. But in reviewing reports from several countries, they argue that such interactions carry some risk, particularly among infants and people whose immune systems have been weakened by disease, chemotherapy or other medicines.

"The risk is not huge. But the trend is that more and more people are sharing their environments with pets, allowing them in their beds, kissing them like crazy," Chomel said in an interview. "They need to know that a risk does exist" from bacteria that live in the mouths of felines and canines.

In their article, to be published in next month's edition of the journal Emerging Infectious Diseases, Chomel and Sun note that pets are becoming increasingly popular in urban households and "have conquered our bedrooms."

According to a recent survey by the American Pet Products Association, nearly half of pet dogs and 62 percent of cats sleep with their human companions.

Among the bacterial, parasitic and viral conditions they may be bringing with them are plague, cat-scratch disease and staphylococcus infections, Chomel and Sun report.

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