You love your cat. And your cat loves you (in its own fashion). But beware—your cat can make you sick.

Cat bites account for less than 15 percent of animal bites treated in emergency rooms, and they are not usually deep. But they pose special risks. Infections caused by cat bites can cause complications such as nerve involvement, abscesses, and a loss of joint mobility, according to a new study that reviewed the records of people who went to Mayo Clinic Hospital for cat bites.

The three-year retrospective published in the February issue of The Journal of Hand Surgeryreviewed the records of 193 such people, 36 of whom were immediately admitted, with an average hospital stay of three days. An additional 154 patients received oral antibiotics as outpatients. Eventually, 21 of these patients were hospitalized.

The most common cause of infection was Pasteurella multocida, an aggressive bacterium found in the mouths of many animals and up to 90 percent of healthy cats. Amoxicillin is commonly used to treat this infection.

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Dr. Brian T. Carlsen, senior author of the study and a hand surgeon at the Mayo Clinic, explained that redness, swelling, increasing pain, difficulty moving the hand, and drainage from the wound are all signs that there may be an infection and that treatment should be sought. “The tendon sheaths and joints are superficial in the hand, and cat bites penetrate easily, seeding those spaces with the germ,” he said.

Commenting on the study’s findings, Dr. Howard Gittelman, D.V.M., hospital director of Animal Medical of New City in New City, N.Y., said, “We have always known that cat bites are more hazardous and likely to cause infections than dog bites because of the resident flora that live in cat’s mouths. Cats have a unique ability to cause cellulitis. People are more prone to cellulitis than other animals.”

Gittelman, who was not involved in the study, also pointed out that cats are also carriers of the Bartonella henselae, which can cause cat scratch fever. “Cats contract Bartonella predominantly from the bites of fleas. It causes streaking of the arms and swollen lymph nodes, and it can cause other nasty diseases,” he said.

He advised, “If someone who is immunosuppressed or on chemotherapy gets bitten by a cat that is a carrier of Bartonella, they should be concerned and seek treatment.”

Other common symptoms of cat scratch fever include a bump or blister where you were bitten or scratched, swollen lymph nodes, and headache.

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When it comes to cats and allergies, there’s good news and bad news for pet lovers. A recent report in the journal Pediatricsfinds that babies who grow up in homes with a dog or a cat are less likely to get sick than children who live in homes without pets. But those who lived with a dog fared better.

Researchers think that exposure to pet dander and the microbes that pets bring from the outdoors into the house could prime babies’ still-developing immune systems and train them early to ward off onslaughts from common allergens and even other bacteria and viruses.

Researchers studied 397 children who were born in Finland between 2002 and 2005. Overall, babies who lived with a dog were 31 percent more likely to be healthy in their first year than babies without a dog, while children in homes with cats were only 6 percent more likely to be healthy than those in cat-free families.

Also fueling concerns about cat parasites and their impact on human health is the discovery by University of British Columbia scientists of an infectious form of the cat parasite Toxoplasma gondii, which causes toxoplasmosis, in beluga whales. These findings have prompted a warning for the Inuit people who eat whale meat.

Cats are this parasite’s natural hosts, and their feces can carry millions of the parasite’s eggs. Most people who have toxoplasmosis never have any symptoms at all—according to the Centers for Disease Control and Prevention (CDC), more than 60 million people in the United States are infected with the parasite. However, it can seriously harm the fetus of a pregnant woman who becomes infected (this is why pregnant women are advised to let others handle cat litter).

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According to work presented at the American Association for the Advancement of Science (AAAS) conference, the parasite has been discovered in over 10 percent of beluga whales living near the Canadian coast, in the Beaufort Sea. Since locals eat whale meat, there is concern that when the meat is prepared or is eaten undercooked, there is risk of infection. “The only way to kill [the parasites] is to freeze them, desiccate them, or boil them,” according to lead researcher Michael Grigg.

It is believed that the whales may have developed the parasite from cat feces getting washed into the water, or that climate change is to blame. Researchers have said that the big thaw occurring in the Arctic is permitting movement of pathogens between the Arctic and the lower latitudes.

All that being said, there are many demonstrated benefits to pet ownership, not the least of which may be simple happiness. Studies have shown that people with pets are less likely to report feeling depressed than people without.

The American Heart Association has linked the ownership of pets (especially dogs, but cats, too) to a reduced risk for heart disease.

And pet ownership is growing: An American Veterinary Medical Association (AVMA) survey shows that singles—both those never married and those recently separated or divorced—are increasingly turning to pets for love and a sense of family.

“It’s interesting to see that more and more single people are discovering the comfort and satisfaction that owning a pet can offer. Pets are powerful, positive influences on our lives, offering unique emotional, psychological, and physical health benefits to their owners,” said Dr. Douglas Aspros, immediate past president of AVMA, in a statement.

According to the CDC, most households in the United States have at least one pet. The CDC also reports that pets are not only good for your mood, but also help decrease blood pressure, cholesterol levels, and triglyceride levels.

So, what can you do to protect your loved ones—whatever species they belong to?

Gittelman says, “All pets can potentially transmit diseases. Make sure pets have an annual physical. Older cats should have a physical two times a year. Make sure children wash their hands frequently, especially before they eat.”

He adds, “We screen for common parasites that may spread disease to pets and family members. We dispense a topical systemic product called Revolution (selamectin) that we give to cat owners to use on their cats once a month to prevent their cats from acquiring infections, including roundworms, hookworms, fleas, ticks, and ear mites.”

“This treatment also prevents owners from acquiring their pet’s infections—because when cats carry the fleas into the house, it is hard to get rid of them.”