Intestinal Worms
in dogs and cats

Tapeworms, Round worms,
Hook worms, Whip worms
Coccidia, & Giardia
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Introduction: Here's a quick list of the common parasites affecting pets in our country.  Some of them can be deadly, some can affect humans, and some just make our pets miserable.

Extermal Parasites

1.  Fleas.  Often cause severe skin irritation and can be a carrier of diseases and tapeworms.  We discuss flea control on another page. 

2.  Ticks.  A carrier of disease, can cause anemia, and can cause fairly severe discomfort.  We discuss tick control on another page.

3.  Mosquitoes.  Carriers of heartworm and other diseases.  Very irritating.  (flying syringes)  We discuss mosquitoes on another page

4.  Biting Flies.  Irritating, and they sometimes lay eggs under the skin that become larvae (bot flies) (cuterebra) (maggots)  We discuss flys a little bit on our page about wounds.

5.  Lice.  Not common anymore.  Easily detected and treated.

6.  Scabies or Sarcoptic Mange.  Very itchy, causes severe dermatitis, and contagious to other pets.  We discuss mange on another page

7.  Demodex Mange.  Can cause severe dermatitis, genetics are a factor, and not contagious.  I've listed this type of mange separately from scabies mange because the treatment is different.  We discuss mange on another page

8.  Ear mites.  Easily detected and treated but getting resistant to the ear mite products sold over the counter.  We discuss ear mites on another page

All the above parasites are external parasites and their control is discussed on other pages on this site.  The seven parasites listed below are internal parasites.  One of the seven internal parasites we worry about is heartworms and we discuss this disease and it's prevention on it's own page.  The six remaining parasites are all intestinal worms or protozoa and that's what this page is about. and I've highlighted the four requiring vigilance below.

Internal Parasites of the Blood

9.  Heartworms.  (Blood)  These parasites are microscopic when they enter the body via a mosquito bite, but grow into a spaghetti sized worm that lives in the blood vessels near the heart where they cause significant disease in both cats and dogs.  We discuss heartworm prevention on other pages. 

10.  Tick borne parasites that cause Lymes Disease, ehrlichia, mycoplasma, babesiosis, and anaplasmosis.  I hope to write about these diseases soon.  Ehrlichia is a rising threat and I talk a little about this on our introductory page to parasites

Internal Parasites of the Intestinal Tract

11. Tapeworms belong to a class of worms called cestodes. There are a bunch of different subspecies of tapeworms, but from a practical stand point in pet medicine, it doesn't matter much because we use the same few cestode killing medicines for all of them. 

But I mention that tapeworms are cestodes, because round worms, hook worms, and whip worms all belong to a class of worms called nematodes.  And this is important because we use a different treatment to control nematodes than we do cestodes.

Tapeworms can occasionally cause severe disease and death but are more often just an irritant to the bowel.  But that's reason enough to treat them if seen.  Tapeworms can be seen on top of the stool as long segmented worms many inches long, but usually all that is seen are just single segments that look like rice in the stool.  Or as these segments are sticky, you can often see little dried, brownish sesame sized segments stuck to the hair near the anus.
(The worms in the picture at the top of the page in a section of dissected intestine are tapeworms)

Tapeworm larvae have to spend part of their life cycle in rodents or fleas so controlling these pests are a big part of keeping your pets free of tapeworms.
Tapeworms have become resistant to over the counter, inexpensive dewormers... to effectively kill tapeworms, you'll need moderately expensive prescription tablets (usually $8-50 depending on the size of your pet.... and for best results this should be repeated)

12.  Roundworms are large intestinal nematodes and the most common worm in puppies and kittens. They occasionally cause serious problems in people ...especially children. So it's very important that all puppies and kittens are dewormed several times when young (most commonly at 2 weeks of age and again every month afterwards for several times.  Usually your vet does this for at the same time he or she gives the puppy or kitten it's initial vaccines.)

This particular nematode worm is easy and cheap to kill but it's not a one treatment affair.  Your pet is constantly exposed to new larvae both from the environment and from microscopic larvae encysted in the muscles from birth. You need to treat your pets multiple times a year.  For your convenience, most products sold to control heartworms also control round worms well. Round worms look like a curled up, 5 inch strand of spaghetti.

I've written about the dangers to people from pet intestinal worms on another page

13.  Hookworms  are microscopic blood sucking intestinal nematodes and not only can they kill your pet and harm your children, but they are getting resistant to the products claiming to control them.  This is why, at least in those parts of the country where hookworms are prevalent, pets need to be dewormed regularly AND have periodic microscopic fecal tests to make sure there are no resistant worms.

I wasn't planning on getting into details, but just so you can picture the potential danger, hook worms (and whip worms which are going to discuss next) bore little holes in the intestinal wall and secrete a heparin like chemical that keeps the little wound from clotting. Then they suck until they are full and then detach themselves leaving a little microscopic hole in the intestine that not only leaks blood out BUT ALLOWS POOP INto the blood stream.  Get enough bacteria in your blood stream and you can get very, very sick very quickly.

14.  Whipworms are another blood sucking, microscopic nematode of the intestines and everything I wrote about hook worms pretty much goes for whipworms.  Except they seem to be a little harder to get rid of from your pens and yards so that your pets keep getting reinfected.  And unlike hookworms, they don't pose a threat to your children.

15.  Coccidia  are little protozoa organisms that cause huge economic loss and animal suffering in poultry and livestock but rarely cause serious disease in pets EXCEPT for chronic debilitating diarrhea in very young puppies and kittens.  I've written about coccidia on another page and also about Toxoplasmosis, a specific type of coccidia that causes birth defects in humans on yet another page.

We can treat this coccidiosis when it occurs but we don't have an effective preventive.

16.  Giardia  is yet another protozoa (sometimes called amoebas) that frequently causes pretty bad gut irritation.  This organism is everywhere, there are a zillion different sub species affecting all mammals, and luckily the  GI irritation (diarrhea and nausea) that they can cause is usually mild and short lived.
We can treat this disease when it occurs but we don't have an effective preventive.  There is a vaccine available for giardia but it hasn't been very successful. (too many strains that are resistant).  (It is because of risking "amoebic dysentery" from organisms like giardia that you shouldn't risk drinking water from a creek or lake without first boiling it or otherwise purifying it)

I've written more about giardia (and also cryptosporidia) on another page.

So, What should you do to protect your pet and family? 
Well, luckily, we pretty much take care of this for you if you bring your pets to us for regular check ups and you use monthly heartworm prevention:

1.  Worm your pet on a regular basis.  Pets that go outdoors in the South should ideally be dewormed every 1-3 months.  Luckily most monthly heartworm preventives also help control intestinal worms

2.  Worm your pet twice a year using a potent dewormer.   We use different deworming products each time to counter resistance.

3.  Laboratory examination of the stool at least once a year.  We usually do this during the midyear wellness exam for dogs.
(I've given up doing routine fecal samples for cats because it's not usually needed for 100% indoor cats and it's too much trouble finding stool samples of outdoor cats)

4.  General cleanliness.  If your dog lives in confined area it's important to keep the stool picked up at least twice a week to minimize the egg and larvae load in the environment. (this will also keep the fly population at bay) Having lots of stool around your yard is also a health hazard to humans... especially to children sitting on the ground.  Both hook worm and round worm larvae can bore into human skin and cause serious disease.  Note; strong sunshine does a pretty good job of killing worm larvae, but larvae thrive in damp, shady areas which are sometimes the same places where children like to play when it's hot out.

5.  Keep your pet clean, fit, and healthy.  Everything is holistic... parasites thrive in filth and overwhelm pets with poor nutrition or immune systems compromised by illness, chronic skin disease, or chronic inflammation.

On This Page:

A quick rundown of all the parasites that threaten the health and comfort of your pet... and sometimes your family.

Then a short discussion about each of the different types of worms and protozoa that commonly cause trouble in the intestinal tracts of dogs and cats.

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Obesity; new information and about Pfizer's new FDA approved treatment


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Information about intestinal diseases
On Other Pages:

Our introductory page to intestinal disease in dogs and cats

Our introductory page about parasites in pets

Giardia & Cryptosporidia


Toxoplasmosis from Cats

Parvo Virus Diarrhea


Problems with the Esophagus



Liver Disease


Food Allergies

Colitis: Chronic problems with the lower bowel

Garbagitis: Acute intestinal upset due to overeating, eating treats, rancid food, and eating inappropriate objects, or eating too much hair.

Diseases people get from pets through worms

Our page about therapeutic diets used to treat intestinal diseases

On Other Pages
There's a complete directory of links at the bottom of the page

Cat Scratch Fever

Diseases people get from pets: Tuberculosis, Plague, and Brucellosis. Pasteurella, Encephalitis, Samonella, e-coli, and Cryptosporidium


Diseases people get from pets from mosquitos, fleas, ticks, and lice
malaria, yellow fever, encephalitis, plague, heartworms, Rift Valley Fever, Lymes Disease, Rocky Mountain Spotted Fever, Tick Paralysis, Monkey Pox, etc

West Nile Disease