Whipworms and Roundworms and Hookworms – Oh my!

by Dr. Kelly | 2nd August 2011

What you don’t know about intestinal parasites can hurt you and your pets!

There are several types of intestinal parasites that can affect our pets. Unfortunately, some of these parasites are zoonotic meaning they can be transmitted to people. This is why we recommend fecal examinations at least once a year for adult animals and more frequently for puppies and kittens. Here are some of the most common intestinal parasites that our pets can get and which ones may be transmitted to people. This is meant to be only a brief overview; for additional, more in-depth, information visit the link at the end of each section. Also, please note, I have only included pictures of what the eggs look like under the microscope to limit the gross-out factor. So if you have a sensitive stomach, you may not want to follow the links as they do have to pictures of the worms themselves on their respective pages.


Where they come from: Puppies and kittens can get roundworms from their mother prior to being born or from her milk. Adult animals can get roundworms from ingesting the stool of other affected animals.
Who gets them: dogs, cats, raccoons
Signs of infection: Weight loss, poor hair coat, pot-bellied appearance (especially in puppies and kittens), vomiting worms, and worms in stool.
Zoonotic potential: Human infection most commonly occurs in children from ingestion of roundworm eggs from a contaminated environment.
Prevention: Most roundworm eggs require 2 to 4 weeks in the environment to larvate and develop to the infective stage. Prompt removal of stool from the environment helps prevent contamination and reduce the risk of becoming infected. Good, regular handwashing, especially for small children and immunocompromised adults, is important to prevent transmission to humans.
More info


Where they come from: Ingestion of infective larvae from the environment, through mother’s milk, larval skin penetration, or by eating prey infected with hookworms.
Who gets them: dogs, cats
Signs of infection: Hookworms literally hook into the intestinal lining and suck blood. Signs of hookworm infectino include anemia, weight loss, lethargy, tarry diarrhea, poor hair coat, and pale gums.
Zoonotic potential: Hookworms can cause cutaneous larval migrans (CLM) in people. The larval stages of the hookworm penetrate the skin and migrate through. The most common people affected are those that are in direct contact with contaminated soil such as plumbers, exterminators, farmers/gardeners, and children. Even sandboxes can harbor hookworm larva so it is important to keep sandboxes covered when not in use.
Prevention: It takes 2-9 days for eggs to hatch and form infective larvae in the environment. Prompt removal of stool helps prevent infective larvae from contaminating the yard.
More info


Where they come from: Ingestion of infective eggs.
Who gets them: dogs, extremely rare in domestic cats of North America
Signs of infection: Colitis, diarrhea, dehydration, weight loss, anemia and in rare cases death. Whipworm infection can mimic other diseases such as Addison’s disease as it can also cause electrolyte abnormalities.
Zoonotic potential: There are rare reports in human medicine but, for now, whipworms are not considered zoonotic.
Prevention: Avoidance of contaminated environments is the best way to prevent whipworm infection in your dog. Prompt removal of stool from the yard helps prevent contamination. However, if your dog has already been diagnosed with whipworms, it is likely that your yard is contaminated and will likely stay that way for many many years. Your best bet at that point is to keep your dog on a monthly heartworm preventative that is also effective against whipworms such as: Advantage Multi, Interceptor, Sentinel, or Trifexis.
More info


Where they come from: Ingestion of fleas or infected rodents. Tapeworms are not directly transmittable through ingestion of tapeworm segments.
Who gets them: dogs, cats
Signs of infection: Mild weight loss or difficulty gaining weight. Animals pass tapeworm segments in their stool.
Zoonotic potential: There are multiple species of tapeworms that can infect our pets. Only one species, Echinococcus, is transmittable to humans. Infection risk is extremely low but humans can become infected by ingesting infectious eggs. The eggs shed in the feces of an infected dog or cat are immediately infectious to humans. Infections of children with the flea tapeworm following ingestion of an infected flea are occasionally reported.
Prevention: Controlling fleas and discouraging your pet from eating rodents that can be infected with tapeworms are the two most important ways to prevent tapeworms.
More info


Where they come from: Transmission is by ingestion of cysts shed by animals or humans in the stool. Infection can also occur through ingestion of contaminated water, food, or inanimate objects or through grooming. Dog strains are not known to infect cats, and cat strains are not known to infect dogs.
Who gets them:dogs, cats, hamsters, guinea pigs, beavers
Signs of infection: Severe, watery diarrhea, dehydration, and lethargy are signs of giardia infection. Giardia can be seen on a fecal examination but the feces must be examined within 30 minutes or less of obtaining the sample to ensure the giardia do not die and are unidentifiable.
Zoonotic potential: Human infections are usually from other humans. Infection from dogs and cats to humans appears to be rare.
Prevention: Avoiding contact with environments that have been contaminated with giardia is key. Prevent ingestion of lake or river water by pets.
More info


Where they come from: Ingestion of infective eggs from contaminated environments is one way dogs and cats get coccidian. They can also get coccidian from ingestion of mice, rats, hamsters, dogs, cats, opossums, or cattle containing extraintestinal stages.
Who gets them: dogs, cats
Signs of infection: Weight loss, dehydration, and (rarely) hemorrhage can be caused by coccidia. Severely affected animals may present with anorexia, vomiting, and depression. Adult animals are less likely to show clinical signs of infection than puppies or kittens due to adults having a better immune system.
Zoonotic potential: Coccidia are not considered zoonotic.
Prevention: Because coccidia are highly transmittable, proper sanitation is important to reducing or eliminating spread. Also, discouraging pets from eating other animals that may carry coccidia is helpful.
More info


Where they come from: Ingestion of infective forms or transfer from mom to kitten (in-utero or through milk) are the two most common routes of trasmission to cats.
Who gets them: cats
Signs of infection: Toxoplasmosis may affect lymph nodes, brain, lungs, heart or the retina. There may be associated fever, weight loss, and lethargy. Congenital infection with Toxoplasma is associated with neurologic disease, birth defects, stillbirth, and ocular disease.
Zoonotic potential: Toxoplasmosis is zoonotic. There is also concern about women being exposed to Toxoplasma for the first time during pregnancy. If antibodies to Toxoplasma are formed during pregnancy, it can cause birth defects. Pregnant women who developed antibodies to Toxoplasma prior to their pregnancy are generally ok but only a human doctor can determine your risk for certain. This is why when women are pregnant, they should not be in charge of cleaning the litterbox.
Prevention: Eggs shed by cats become infective in 1-5 days and survive for months to years in the environment. Scooping the litterbox daily and washing your hands well afterwards are the best ways to prevent reinfection of the cat as well as to prevent trasmission to people.
More info

Occasionally, we may suspect parasites but not be able to find them on fecal examination. This is because many of these organisms are shed intermittently meaning that they are not always present in the stool even when infection is present. Routine deworming, such as the majority of heartworm preventatives, helps to reduce the likelihood of your pet having many intestinal parasites. Most heartworm preventatives are effective against roundworms and hookworms. Some, such as Sentinel, Interceptor and Trifexis, are effective against whipworms as well. This is why a yearly fecal exam is highly recommended for all pets along with monthly heartworm preventative.

If you have questions about what intestinal parasites your heartworm preventative treats or suspect your pet may have intestinal parasites, please give us a call at (636) 561-9122.


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