Intestinal parasites are organisms that inhabit the intestinal tract of animals. They complete parts of their life cycles by using the animal host for nutrients in the form of digested food or blood. During their life cycles, within the host, they cause varying degrees of illness. This usually means inappetence, vomiting and/ or diarrhea.

There are many intestinal parasites that can infest your pets, but only a few are frequently seen and therefore covered in this article. Roundworms, hookworms, whipworms, tapeworms, and coccidia can routinely cause health concerns for your pet. If annual fecal (stool) samples are not examined and monthly preventative medications are not given, you can put your pet and yourself at risk. It is important to know that some of these organisms can even cause human health (zoonotic) concerns.

Toxocara canis LifeCycle roundworm:
(click to enlarge) 
Roundworms or nematodes are free living intestinal parasites that can be transmitted directly from animal to animal via ingestion of an infective egg from the stool. They can cause digestive upset in all dogs and cats but are most serious in the puppy and kitten. With young animals they can cause stunting, weakness, loss of appetite, and even life threatening obstruction to the bowel. This is a parasite that also is a possible health risk for humans. Infestation of children is a particular concern as the larvae can migrate thru a variety of organs in the body. Repeated deworming of puppies and kittens along routine annual fecal examinations is essential to the control of this potential zoonotic threat.
 
Hookworms are intestinal parasites that have a hook-like mouthpart which attaches to the lining of the intestinal wall. They live off of blood taken from their dog or cat host and can therefore cause anemia, along with digestive upset, especially in the puppy and kitten. Their eggs are passed in the stool and then hatch as larva. These larva persist in the soil for weeks or months until being swallowed by an animal or burrowing into the skin of their host. This parasite is also a possible public health risk. The larva can also burrow into human skin and cause “cutaneous larval migrans” or more commonly known as “ground itch”. This once again underscores the need for routine diagnosis and treatment of infected dogs and cats.
 
Tapeworms come most commonly from the ingestion of a flea by your pet. Dogs and cats can also become infested by eating rabbits or mice containing the parasite within their muscle tissue. This worm does not cause a life threatening condition for dogs or cats but is transmissible to people (especially kids) if they might unintentionally eat a flea. Once infested, dogs and cats seem to show irritation at their rectum by licking and scouting. Small white segments can many times be seen then on the stool or around the tail region. Ingestion of these segments, however, does not cause a re-infestation. Deworming, by your veterinarian and then routine use of flea preventative medications is essential to successfully eliminate this parasite.
 
Whipworms infest the large intestine of dogs and occasionally cats, causing a diarrhea which can sometimes be bloody. Passed in the stool, the eggs of this worm are very resistant and can exist on the ground for months to even years. Ingestion of infective eggs from the soil by your pet is the route of infestation. Deworming and then using certain Heartworm Preventative medications on a monthly basis is one of the best ways to control this parasite. This is a worm that also presents no zoonotic concern.
 
Coccidia are one-celled organisms (protozoa) that can inhabit your pet’s intestinal tact and its lining. Most infections cause no noticeable symptoms. In the puppy, kitten, and debilitated adult animals this parasite however can cause significant life threatening diarrhea, vomiting, and dehydration. After infecting their host, the coccidian multiply by replicating within the cells lining the intestine. The cells then rupture, releasing immature coccidia (oocysts) into the stool. The oocyts can then survive in the soil for some time where they are ingested by a unsuspecting pets. Another way to indirectly become infected is by ingesting a coccidian containing mouse. Luckily, treatment is available for symptomatic animal and this parasite is not contagious to people.

The potential threat that these few parasites pose to your pet shows how important good hygiene and prompt disposal of dog and cat feces is. By cleaning up after your pet it minimizes the risk of spreading these parasites to other animals (and in some cases to people). Routine fecal checks by your veterinarian are also essential. Today, many of the prescription Heartworm Preventative medications will also help to control these parasites on a monthly basis. At Kansas City Veterinary Care we recommend annual fecal evaluations for parasites and year round treatment with flea and heartworm preventative medications to safeguard you and your pet from these noxious parasites.

Related Links
Centers for Disease Control and Prevention: Parasites
CDC: Health Pets Healthy People