Most people don't think too much about their pets' intestinal health unless problems occur, but your pet can carry intestinal parasites even if it isn't experiencing vomiting or diarrhea. You may not see worms in the stool even if your pet has worms, and not all intestinal parasites are big enough to see with the naked eye. Some are single-celled organisms which, despite their small size, can still make your pet quite sick.
Your pet can become infected with parasites in many different ways. It may drink contaminated water, come into contact with other infected animals, or come into contact with contaminated soil or surfaces. Certain parasites can be transmitted through contact with fleas or by eating uncooked flesh (such as cats that eat mice), and other parasites can be transmitted to unborn or infant animals by direct contact with an infected mother.
Signs of parasite infections may include changes in appetite, coughing, diarrhea and/or bloody or dark feces, weight loss, rough or dry hair coat, skin irritation and itching, or an overall poor body condition. Some pets may show no obvious signs of parasite infection, so it is best to have your pet checked as part of his or her annual checkup by bringing a fecal sample with you to the vet's office.
With the exception of tapeworms, which expel broken worm segments in the feces, most intestinal parasites are never seen in a pet's bowel movements. The mature parasites grab on to the walls of the intestine and live there for their entire life cycle. Only the tiny parasite eggs are released, and this is what your pet's doctor looks for under the microscope.
Different parasites require different medications for treatment, which is why an accurate diagnosis is required. Some may be treated with over-the-counter medications while others require prescriptions. Some may be easily treated with one or two doses, but if contamination of the home environment if suspected then ongoing treatment may have to be discussed to prevent reinfection.
Some of these parasites may be contagious to people, so extra precautions must be taken while cleaning these pets and decontaminating areas where the pets have eliminated. People with weakened immune systems (recovering from other illnesses, chemotherapy, HIV positive, etc.) must be especially careful to keep their pets parasite-free.