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350 South Huntington Avenue, Boston, MA 02130
(617) 522-7400
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Angell Animal Medical Centers – Boston

350 South Huntington Avenue, Boston, MA 02130
(617) 522-7282
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293 Second Avenue, Waltham, MA 02451
(781) 902-8400
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(339) 970-0790
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Angell at Nashoba – Low-Cost Wellness Care

100 Littleton Road, Westford, MA 01886
(978) 577-5992
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Animal Care and Adoption Centers – Boston

350 South Huntington Avenue, Boston, MA 02130
(617) 522-5055
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Animal Care and Adoption Centers – Cape Cod

1577 Falmouth Road, Centerville, MA 02632
(508) 775-0940
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400 Broadway, Methuen, MA 01844
(978) 687-7453
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David Jimison, DVM
Angell General Medicine Service


Few things compare to that feeling of finding worms in your dog’s feces.  As veterinarians, we are often obsessed with your dog’s stool – volume, frequency, color, and consistency.  Poop can be an invaluable diagnostic tool. It can tell us how well an animal is eating, if they are experiencing an intestinal bleed, and if there are any other organisms present causing trouble, such as parasites.

How does my pet pick up parasites, you may wonder? Well, let’s suppose you and your dog go somewhere frequented by other dogs: such as a dog park or common hiking trial.  If another dog who already has parasites poops on the ground, it could serve as a source of infection to yours and other dogs.  There are then several ways your dog could become infected. Your dog could walk through the contaminated soil, then later groom themselves and ingest the eggs from their fur.  Or if the ground was wet from rain water, your dog could to drink the water and ingest the infectious larva.  Or your dog could actually eat the poop of another dog. Gross!  Parasites are generally picked up by dogs through oral ingestion. However, there are some that can be inhaled or can burrow through breaks in the skin.

Very young animals are at higher risk for contraction of parasites because of their decreased immune system.  Some parasites, such as Roundworms, have been shown to infect more than 30% of dogs less than 6 months of age and more than 25% of cats.  In some cases they can be born with infections already present.   Puppies and kittens that are infected while still in the uterus can have trouble gaining weight, poor coat quality, and severe infections could even be fatal.  Fortunately, most dogs with roundworms show no signs at all, or will only have a slight potbelly appearance.

Now your little poop eater is having a lovely case of room clearing, watery diarrhea. Naturally, all over the antique area rug.  What do you do?

A trip to your vet and a fecal examination reveal that your pet does in fact have a parasite infection.  There are many different parasites that can infect dogs and cats, such as roundworms, hookworms, whipworms, coccidia, and giardia, to name a few. Fortunately, most are easily treated with a combination of deworming medications, anti-diarrheal medications, and high fiber bland diets.  However, in some cases of resistant infections, alternative medications may be necessary. Please consult with your veterinarian as to the appropriate course of treatments for your pet.

What can I do to try to prevent parasites?

During their first  months of life, many puppies and kittens are routinely dewormed against common intestinal parasites during their routine vaccination visits with their veterinarian.  Additionally, it is recommended to initiate regular parasite prevention at that time.  Many internal parasites can be prevented with monthly medications.  Medications containing pyrantel are effective for roundworms and hookworms. And milbemycin based medications will prevent roundworms, hookworms and whipworms.  There are also topical preventatives available for internal parasites, such as selamectin for roundworms and hookworms, or moxidectin for roundworm, hookworms, and whipworms.  Please discuss with your veterinarian what would be the best option for your pet’s lifestyle.

One important thing to remember is that the majority of internal parasites take time to develop in the environment into the infectious stage. For example, roundworm eggs take about 30 days in the environment before they develop into the infectious stage. Once in the environment, some eggs can persist there for years and be a continual source of infection.  The best way to prevent parasite eggs from contaminating the environment is to always dispose of your pet’s stool promptly after he defecates.

Some parasites are considered to be zoonotic meaning they can be transmitted from animals to people. In a healthy adult with a normal immune system and proper hygiene, the risk for infection is low. However, with immunocompromised people, such as the very young, the very old, people on immunosuppressive medications, or people with immunosuppressive illnesses, these parasites can be an important cause of illness.  If there is anyone in your home that fits that criteria, please have your pet’s stool regularly screened for the presence of internal or intestinal parasites. Zoonotic parasites that can also infect people can have a wide range in symptoms from gastrointestinal disease to skin problems or blindness. Annual fecal testing can be an important way to screen for potential carrier animals.  Please bring a fresh fecal sample with you to your pet’s annual veterinary wellness exams.

The Companion Animal Parasite Council ( compiles information from the major laboratories around the country in order to better understand the prevalence of certain parasites throughout the country. Please visit their website to check the prevalence of parasites in your area. They also an excellent resource for more information about each specific parasite.  In Massachusetts 1 out of 58 dogs and 1 out of 22 cats tested positive for roundworms. For hookworms, 1 out of 53 dogs tested positive. And for whipworms 1 out of 213 dogs tested positive.

Parasites are only one of many causes for diarrhea. They can sometimes be a sole cause, especially in young animals. They can sometimes be present in asymptomatic animals. And in healthy adult animals, treatment may not be even be necessary.  Other times, parasites could be present, but not be the sole cause of disease.  In such cases, repeated courses of antibiotics and deworming medications could be harmful to the normal healthy bacteria of our pet’s GI tracts.  If medications are not working or if your pet is having unusual clinical signs, perhaps another cause should be considered. Always consult your veterinarian before starting treatment.  Parasites can certainly be a bother. But with proper hygiene, hand washing, prompt fecal pick up, and monthly parasite prevention, the overall risk from intestinal parasites can be minimized significantly.


For information about Angell’s General Medicine service, please visit or call 617-522-7282.

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