|Intestinal parasites are fairly common in dogs and cats, and can cause varied symptoms from digestive tract signs (including diarrhea, vomiting, abdominal distention, weight loss along with changes in appetite) to respiratory symptoms (coughing, difficulty breathing).
Most intestinal parasites are not seen visually in the stool samples by owners, and are usually identified by finding their microscopic eggs in a stool check performed by the veterinarian.
Exceptions to this would include tapeworms, which are often identified by the presence of mobile, flat white rice-like segments seen in the stool or near the anal opening or tail base of affected pets. Clients also occasionally see pets vomit long stringy worms known as roundworms.
Because the most susceptible populations are young puppies and kittens, it is important to not only check stool samples at least twice from the ages of 6 to 16 weeks of age, but also to worm these youngsters with broad-spectrum wormers such as Pyrantel, Strongid or Nemex. This is especially important when there are young children present in the house, as certain parasites such as roundworms and hookworms may be transmissible to people.
With adult pets, I recommend checking stool samples at least once yearly. Monthly heartworm preventative medications such as Sentinel and Heartguard Plus not only prevent heartworm infestation, but also control and treat many common intestinal worms, which is why it is recommended to keep dogs and cats on these preventatives year-round. Parasites such as whipworms and Giardia are sometimes difficult to identify in stool samples, so veterinarians will often worm pets for these when clinical symptoms of diarrhea, weight loss or vomiting are present in adult pets.