Intestinal Parasite Roundup

So your pet has worms. You receive a call from your vet’s office about a positive fecal test result. Or, worse yet, see worms in your pet’s stool. Understandably clients often have lots of questions and concerns about intestinal parasites (aka worms). How can their dog or cat have worms if they don’t have diarrhea? Why are the worms not always visible in the stool? Can their family get sick? If a fecal test is negative, can their pet still have parasites? How can their pet get worms in the winter?

The following article aims to give a general overview about the most common intestinal parasites we see in DC and on Capitol Hill. Be sure to follow your veterinarian’s treatment recommendations if your pet is diagnosed with intestinal parasites.

Giardia is a common but often misunderstood parasite. First of all, it is not actually a worm. It is a protozoal parasite that is only visible microscopically. The really annoying thing about Giardia is that it can exist in a cyst form which allows it to live outside the host, contaminating the environment and waiting to infect another host. Contaminated water is a common source of Giardia infection, but pets can also get Giardia by ingesting the cysts while grooming their haircoat. People can get Giardia, but it is uncommon for them to get it from their dog or cat. Zoonosis (transmission between humans and animals) is possible but rarely occurs.

Diagnosis of Giardia can be made by identifying the cysts under the microscope, which can be tricky since they are only shed intermittently by the host. Diagnosis has become easier using a special test called ELISA that tests for Giardia proteins. If your pet has Giardia be sure to bathe them while they are being treated to remove any cysts from the haircoat to prevent reinfection.

A common frustration for owners is when one of their pet’s fecal samples keeps testing positive for Giardia despite being treated. Cleaning the environment, ideally with a 1:32 dilution of bleach and water, has been proven to kill Giardia cysts. Obviously diluted bleach is not an ideal household cleaner for many items. Also, asymptomatic animals may not require treatment as their immune-system may be able to deal with the infection on its own. However, if your pet has clinical signs (diarrhea, vomiting) from Giardia, treatment is recommended.

Whipworms, like Giardia, can also be a tricky parasite to diagnose. The eggs are only shed intermittently in the feces, and sometimes clinical signs develop before the eggs are visible in the feces. Like Giardia, whipworm eggs can live in the soil for years and are resistant to desiccation, extreme temperature changes, and UV radiation. Hosts are infected by ingesting the eggs from soil or other substances contaminated with the eggs. The adult worms have a thin strand with a thicker end on one side, which looks like a whip, hence then name. Whipworms live in the intestines and can cause diarrhea, sometimes with mucous and blood.  If suspected from clinical signs, or diagnosis is confirmed with identification on a fecal test, treatment with deworming medication will be advised. Several medications can be used to treat whipworms, so talk to your veterinarian about which one is best. Some heartworm preventions, but not all, are also labeled for the treatment and monthly prevention of whipworms.

Hookworms are like vampires of the intestinal parasite world. They attach to the intestines with their mouth, digest intestinal issue, release an agent to prevent blood from clotting, and suck the blood. There are several routes of transmission including ingestion of the larvae orally, through a wound, in breast milk, or even eating another animal (like a rodent) that has hookworms. If the animal is infected through the skin they can get skin lesions, typically on their feet. After penetration through the skin the parasites travel via the lymphatic system and veins to the lungs and are finally coughed into the trachea. Then they are swallowed and attach to the small intestines and mature to adults. Very young puppies and kittens can even die from hookworm infections due to anemia from blood loss. This is one reason why routine biweekly deworming is recommended in puppies and kittens starting at two weeks of age until at least eight weeks of age, sometimes longer. Severe illness is uncommon in adults, but infected animals can have diarrhea, weight loss, and anemia.

Unlike whipworms, hookworm eggs do not survive freezing temperatures and only live for a few months in the soil during ideal weather conditions. And also, unlike the more sneaky Giardia and whipworms, hookworms are usually readily apparent on fecal tests. Unfortunately hookworms are a threat to humans as well. They can penetrate the skin of humans and cause a condition called cutaneous larval migrans, which causes really itchy skin lesions. Prevention for humans includes covering the skin with shoes and gloves while gardening and covering children’s sandboxes when not in use to prevent fecal contamination.

Roundworms have a similar mode of transmission to hookworms, though they are not transmitted through the skin. However, dogs and cats can be infected in utero from their mother’s placenta. One gross fact about roundworms is that they can be expelled in vomit or fecal material. If you see spaghetti-like worms in vomit or feces your pet may have roundworms. Roundworms can also infect humans, usually young children, who ingest fecal material or material contaminated with fecal material. Always wash your hands after picking up your pet’s poop.

If you see something that looks like white rice in your pet’s stool, they might have tapeworms. Dogs and cats commonly get tapeworms from eating fleas. If you see tapeworm segments in the poop, your pet has at least eaten a flea and may have fleas still on their skin. Fecal testing is not reliable for diagnosis since the eggs and tapeworm segments may not be visible. Direct visual examination of the stool is usually sufficient for diagnosis. Treatment of both the tapeworms and fleas is likely necessary to get rid of the issue. It is possible for people to get the same species of tapeworm that dogs and cats get, but it is unlikely because they would need to eat a flea too.

One other parasite of concern is the heartworm. However, it is not an intestinal parasite, so I won’t be covering it here. In brief, the heartworm parasite is transmitted from mosquito bites and grows into worms in the lungs and heart in dogs and less commonly cats. Heartworm disease is a serious, life threatening infection, so monthly, year-round heartworm prevention is advised for dogs and cats that go outside.

Please be a responsible DC pet owner and pick up your pet’s poop. Keep your pet on monthly heartworm prevention, which prevents some, but not all, intestinal parasites. Follow your veterinarian’s recommendation for annual or semi-annual fecal analysis and treatment of intestinal parasites, and recheck fecal testing to keep your precious pet free of worms. 

Dr. Brittany Cartlidge is an associate veterinarian at AtlasVet (The Atlas District Veterinary Hospital) 1326 H St. NE, 202-552-8600. Dr. Cartlidge graduated from the University of Florida School of Veterinary Medicine in 2008. 


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