Preventing Intestinal Parasites in Pets and People


The very word makes you cringe, doesn’t it?

Worms are creepy.

All worms. Even the ones you fish with. No wonder your wife requires that you put hers on the hook.

Our pets can be worm free, from both intestinal worms and heartworms. (Click Revolution  to read more of what’s Dr. James W. Randolph has to say about using Revolution for heartworm prevention.) We will also discuss heartworm preventives that prevent certain intestinal parasites at the same time they are preventing heartworms. These include Interceptor, Sentinel, Revolution and Heartgard Plus.

A commonly-asked question about worms is, “Where do worms come from?”   The answer varies according to the type of worm.

In dogs and cats roundworms most commonly come from the mother dog or cat and can be passed from the dam to the offspring while they are still in the uterus or through the milk when young begin nursing. Roundworms also can be contracted by contact with stool that has infective roundworm larvae. There are several species of roundworms. They cause vomiting, diarrhea, weight loss and can even be present in such large numbers that they totally obstruct the intestinal tract.

Hookworms can be contracted by puppies and kittens in the same three ways as roundworms, and infect adult animals more commonly than roundworms (though it certainly is not considered unusual for adult animals to have roundworms). Animals may also become infected by hookworms when walking on soil that harbors hookworm larvae, even long after the stool is gone. There are three common species of hookworms. They, too, cause vomiting, diarrhea and weight loss and not uncommonly a bloody stool.

Whipworms are parasites that most-readily infect dogs (they do not affect cats) that come in contact with infected stool. Any age of dog may be affected. The most commonly-encountered species is Trichuris vulpis and they, too, cause vomiting, diarrhea (usually with mucus and straining) and weight loss. Whipworms can be difficult to diagnose as adult worms often pass small numbers of eggs and do so infrequently. This scenario can cause multiple consecutive stool tests to be negative even though whipworms are present in the intestinal tract. Whipworm infestation may be confused with chronic colitis.

Interceptor is a monthly heartworm preventive chewable tablet which, with one ingredient, prevents heartworms and prevents all three intestinal parasites listed above. Interceptor is also approved for use in cats as a heartworm preventive. It is manufactured by Novartis.

Sentinel, a cousin monthly heartworm preventive chewable tablet contains Interceptor’s ingredient.  It also contains  an additional flea-prevention ingredient that causes any adult fleas that feed on your dog to lay eggs that are defective. Those eggs, then, will not be able to mature to adult fleas. Sentinel is also a Novartis product.

Revolution is a heartworm preventive that also prevents hookworms and roundworms in cats, but has no such label claim in dogs. Revolution is marketed by Pfizer Animal Health.

Heartgard Plus is a monthly chewable heartworm preventive that also prevents both roundworms and hookworms. Heartgard Plus is available in a cat or dog formulation. It is marketed by Merial.

The above descriptions of these worms’ effects on pets gives us pet lovers sufficient reason to treat and prevent intestinal worms in our dogs and cats, but there is another extremely important reason for controlling worms.


No, it’s not a huge proboscis roaming around your local zoo. “Zoon” is a prefix that refers to animals, “noses” comes from the Greek word “nosos”, meaning disease. So, a zoonosis is a disease transmitted from an animal to man.

Roundworms cause the most devastating problems in people, usually resulting from the larval stages migrating through a person’s brain, spinal cord, eyes and/or abdominal organs. All people are at risk by coming in contact with stool, but children and immunosuppressed adults are most likely to become affected.

Hookworms are transmitted to people the same way, but the disease process is usually limited to a skin rash. Still, who wants hookworm larvae burrowing around under his skin?

While whipworms have been documented to infect people the condition is uncommon, or at least uncommonly diagnosed.

Some basic steps are important to protecting both pets and people:
1. Give dewormers and preventives on schedule as directed by your pet’s doctor.
2. Dewormings must come in pairs, as deworming medications can kill only adult parasites. Parasites that are immature at the time of the first deworming will be mature by the time of the second deworming and thus will then be killed. Usually dewormings are given two to four weeks apart.
3. A followup stool test is necessary to know whether all of the parasites have been eliminated and whether additional parasites have become a problem. The followup stool test usually comes two to four weeks after the second deworming.
4. Pick up your pet’s stool as soon as he “goes” in the yard or litterbox.
5. Dispose of the stool down the toilet or in the garbage.
6. Wash your hands thoroughly with soap and water if you come in contact with your pet’s stool or contact soil that may have been contaminated by pets’ stool. This is especially important in public playgrounds where pets are allowed or wildlife roams.
7. Visit the CDC’s Web site for more information.

Tapeworms also infect both dogs and cats and there are two major categories. The most common one uses a flea as an intermediate host (meaning part of the life cycle of the tapeworm must occur in the flea). The flea dies when it is swallowed but the tapeworm matures.  It then attaches to the pet’s intestinal tract and passes packets of eggs so that more fleas may be infected, perpetuating the species. The other type of tapeworm comes from eating the intestines of wildlife, such as rats, mice, rabbits and squirrels.

While some heartworm preventives include a monthly treatment for tapeworms, the first line of defense for tapeworms is flea control and prevention, as well as keeping your pet from consuming wildlife.

In summary, intestinal worms can cause illness in pets and people. Heartworm preventives Interceptor, Sentinel, Revolution and Heartgard Plus can help prevent intestinal parasite infestation in pets. Safety measures are listed that can prevent health problems in people, the most basic of which is effective handwashing.

See you tomorrow, Dr. Randolph.

To read more about intestinal parasites, click here to visit our Intestinal Parasites Category List


No comments yet

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.