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Vomiting or Diarrhea

Cats and dogs vomit on occasion, often without being seriously ill. "A puppy who's eating and playful and has been outside eating leaves and junk and vomits and then goes back about his life" doesn’t worry Meadows much, she says.

But a pet that vomits, especially several times in one day, acts lethargic, and lacks appetite needs a veterinarian's attention, according to experts.

Another serious pet symptom: blood in the vomit or throwing up digested blood that looks like coffee grounds. Gastric ulcers can cause bloody vomit, and so can swallowing a foreign object that irritates the stomach. Veterinarians tell WebMD that they have treated dogs and cats that have gulped down sharp bones, socks, underwear, mittens, towels, string, tinsel, corn cobs, fish hooks, and toy soldiers.

"I had a dog swallow a steak knife right off the table, like a sword swallow," says Sandra Sawchuk, DVM, clinical instructor at the University of Wisconsin-Madison School of Veterinary Medicine.

Vomiting or diarrhea can stem from many other causes, too, including gastrointestinal illnesses or parasite infections that include hookworms, roundworms, whipworms, or giardia, Stickney says.

Blood in the stool is also a warning sign that a pet needs to see the vet.

To prevent human exposure to parasites, such as hookworms and roundworms, Meadows suggests regular de-worming of pets. That's especially important if anyone in the household has a weakened immune system, such as from cancer or AIDS, or if small children play in areas where pets defecate.

Lack of Appetite or Decreased Activity

These two pet symptoms are vague, but if they persist, a veterinarian should check for causes. Dogs and cats stop eating for a host of reasons, including fever, pain, or stress. "A reduced or absent appetite, especially if it lasts for more than 24 hours, is a reason to bring your animal to the veterinarian," says John Randolph, DVM, diplomate of the American College of Veterinary Internal Medicine and professor of medicine at Cornell University’s College of Veterinary Medicine.

Typically, cats suffer more dire consequences when they stop eating, according to Sawchuk. "A dog may be a picky little snit and doesn't eat his dinner because he's waiting for human food," she says. "With cats, you've got to be real careful because if they just even go a couple of days without eating, especially an overweight cat, they can develop fatty liver." In this potentially fatal disease, excessive accumulation of fat in the liver can cause liver failure. A cat that stops eating should see a vet promptly because fatty liver needs to be treated immediately.

What about this pet symptom: the cat or dog whose energy level drops? "It's just one of those very vague things that tell us that something is not right," Sawchuk says. Many things can cause lethargy, including major problems, such as heart disease.

A pet whose lethargy can't be pinned on an obvious reason, such as from an extra-long run at the dog park, may need to visit the vet, especially if other symptoms arise, such as change in exercise tolerance, weakness, collapse, or loss of consciousness.

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