Table of Contents
Diarrhea and worms in dogs
If you have a puppy under 6 months of age with diarrhea then chances are your puppy has worms. However, the majority of dogs older than 12 months of age have no identifiable cause for diarrhea. In these dogs, fecal tests are negative. The cause of acute diarrhea is typically attributed to a short lived irritation of the intestinal tract. Many times this is assumed to be secondary to dietary indiscretion, a change in diet, or stress.
The two most common worms in puppies are roundworms and hookworms. If you give your dog a monthly heartworm preventative already, you are most likely also treating for roundworm and hookworm every month. Select heartworm preventatives also treat whipworm and tapeworm infections, and a few others also treat fleas, mites and ticks.
The only two heartworm preventatives for dogs that do not provide protection from intestinal parasites are: Proheart 6 and 12 injections and Revolution top spot for dogs.
Most canine heartworm medications also treat for worms every month
The heartworm medication with milbemycin and moxidectin are able to treat and prevent hookworm, roundworm and whipworm.
Pyrantel is added mostly to heartworm formulations that contain ivermectin to extend the efficacy to include roundworms and hookworms. In Simparica Trio, the dose of moxidectin is insufficient to reliably treat roundworms, so pyrantel is added.
Praziquantal is added to any heartworm medications to extend efficacy to include tapeworm treatment.
The chart below summarizes heartworm preventatives and their efficacy against intestinal parasites, fleas, ticks and mites.
| Heartworm product | How given | Round worm | Hook worm | Whip worm | Tape worm | Adult flea | Flea larvae | Ear mite | Skin mite | ticks | Cost SmallDog 6 Month |
| Heartgard plus ivermectin | oral | X | X | $40 | |||||||
| Interceptor plus milbemycin | oral | X | X | X | X | $40 | |||||
| Sentinel milbemycin | oral | X | X | X | X | $48 | |||||
| Sentinel spectrum milbemycin | oral | X | X | X | X | X | $52 | ||||
| Trifexis milbemycin | oral | X | X | X | X | $112 | |||||
| Tri Heart plus ivermectin | oral | X | X | $22 | |||||||
| simparica trio moxidectin | oral | X | X | X | $48 | ||||||
| Iverhart plus ivermectin | oral | X | X | $25 | |||||||
| Iverhart max ivermectin | oral | X | X | X | $35 | ||||||
| Revolution selamectin | topical | X | X | X | X | $67 | |||||
| AdvantageMulti moxidectin | topical | X | X | X | X | X | $113 | ||||
| Proheart moxidectin | injection | Vet varies |
Common worms in puppies
Roundworm and hookworm are the two most prevalent intestinal worms found in puppies. Both roundworm and hookworm can be transmitted by nursing an infected mother. Roundworms are also able to infect a puppy as they are developing in utero.
Mothers who are on monthly heartworm prevention with efficacy against hookworms can still sometimes infect their young. This is because hookworm larvae can lay dormant in muscle tissues. The larvae are reactivated in pregnancy and migrate to the mammary glands and get passed onto nursing puppies.
The other major intestinal worms of dogs are the whipworms and the tapeworms. Both of these worms are acquired from the environment. Whipworm is only acquired by ingesting eggs present in contaminated soil or stool. Tapeworms are acquired by ingesting an intermediate infected host: typically fleas or rodents. The most common tapeworm of dogs and cats is due to eating fleas during grooming. A more rare and serious form of a tapeworm in dogs is from eating an infected rodent.
When we test for GI parasites in the veterinary office, the most common fecal testing screens for the following worms: roundworm, hookworm and whipworm and tapeworm. It also screens for protozoal infections for giardia and coccidia.
Infections that cause diarrhea in dogs besides worms:
Protozoal causes of diarrhea in dogs
The most common infectious causes of diarrhea besides worms are due to giardia and coccidia. Giardia and coccidia are single celled protozoa that can be found in soil contaminted with stool. These organims spend part of their life cycle in the cells lining the intestine and this can sometimes cause diarrhea, and most commonly only in puppies.
Fortunately, most adult dogs infected with giardia or coccidia have no symptoms. In fact, the Companion Animal Parasite Council advises that treatment is optional for these infections in asymptomatic adult dogs.
Other infectious causes of diarrhea in dogs are from viral and bacterial infections. Routine fecal exams don’t screen for viral and bacterial causes. However, in some more severe cases of diarrhea your veterinarian may choose to screen for viral and bacterial infections with a fecal PCR or a parvovirus snap test.
Viral and bacterial causes of diarrhea in dogs
Viral causes of diarrhea in dogs include: parvovirus, coronavirus, canine adenovirus and distemper virus. Parvo virus is well known to cause acute bloody diarrhea and severe illness. Distemper typically starts with ocular and nasal discharge and progresses to fever, coughing, lethargy, reduced appetite, vomiting, and diarrhea. Canine adenovirus is related to hepatitis virus and causes severe disease of the liver and diarrhea can be a sequelae. Coronaviruses cause mild diarrhea in young animals. Common core vaccines for dogs protect dogs from these viral infections.
Some triggers of diarrhea are intestinal bacterial flora imbalances which enhance the growth of bacteria which express toxins such as clostridia. Other bacterial causes of diarrhea in dogs include : campylobacter, salmonella and ecoli.
This useful article tells you home remedies for how to treat diarrhea at home.
Symptoms of worms in puppies:
Puppies that have intestinal parasites can have a variety of symptoms. The most common signs are a pot bellied appearance and diarrhea.
More severe infections can cause coughing, nasal discharge, vomiting, decreased appetite, poor weight gain, poor coat quality, ascites and anemia.
Roundworm symptoms in dogs
Puppies can develop coughing and even pneumonia from heavy worm burdens with canine roundworm as the larvae migrate to the lungs as part of their life cycle.
Severe roundworm infestations in puppies can also cause thickened intestines and even partial or complete GI obstruction. The heavy worm burden will lead to a change in the composition of the bacterial flora of the intestinal tract and gas formation.
Hookworm symptoms in dogs
Severe hookworm infections can lead to bloody diarrhea and anemia as these worms attach to the inside of the lumen of the GI tract and induce bleeding. Over time this blood loss can lead to chronic iron deficiency anemia, chronically loose and bloody stools, poor coat quality, weight loss, stunted growth , poor stamina and physical condition and sometimes circulatory shock/collapse.
Whipworm symotoms in dogs
Whipworms embed themselves in the lining of the cecum and colon. Because the infection comes from contact with infected stool or soil in the environment, whipworm infections are more prevalent in adult dogs and many adult dogs can have asymptomatic infections. However, puppies suffer from more symptoms of disease with infection. They can have stunted growth, cyclical diarrhea, weight loss, lethargy and anemia. Dogs may suffer from diarrhea from a whipworm infection before it can be diagnosed as there is a long life cycle before eggs are shed in the feces. Detecting eggs in the feces is how most whipworm infections are diagnosed.
Giardia symptoms in dogs
Giardia is not a worm, but a common protozoal infection of puppies that can cause symptoms of intermittent and chronic diarrhea, or no symptoms at all. The age of the puppy, their clinical , nutritional and immune status all are factors in whether or not they develop diarrhea from a giardia infection
Luckily, the severe manifestations of worms in puppies is not seen very often in puppies that are receiving basic care. Common practice for deworming puppies is to deworm them every other week from the time they are 2 weeks old until they start taking a monthly broad spectrum parasite control with a heartworm preventative.
What do worms look like in your dog’s poop ?
The main body of a whipworm is only about 1-2 cm in length with a long thin lash attached which is 4.5cm to 7.5cm. They are rarely seen by owners because they attach to the lining of the cecum and large intestine.
Roundworms are thicker and longer at 1.5 to 6 inches in length. Roundworms look like strands of spaghetti and are often seen when dogs vomit them up or pass them in their stool.
Tapeworms can be up to 6 inches in length and segmented into 1/8th inch flat pieces that can break apart like grains of rice. If the segments that house the eggs do not break apart in the stool sample, a routine fecal flotation may not identify this infection.
Most often, a common tapeworm infection is identified by the flat grains of rice segments clinging to the fur around the anus or by the longer segments that are passed in the stool.
Hookworms are the smallest of all the “common worm” varieties. They are only 1-2 cm in length and very thin. They can be difficult to see with the naked eye. Hookworms, like whipworms, are rarely seen because they also burrow into the intestine.
Can worms be passed from dog to human by licking or sleeping next to your dog?
Infections that can spread from dogs to people are called zoonotic. Worms are spread by ingestion of an egg found in the stool of an infected animal or by ingesting an intermediate host (typically a flea or a rodent) carrying the larvae of the worm.
The good news is worms are generally not able to infect a person during close casual contact such by your dog licking you or sleeping next to you. You are even more protected if you give your dog a monthly heartworm preventative that has a monthly dewormer. (See the chart above)
The most common ways people are infected by worms that infect dogs are during activities such as gardening without gloves, crawling on the ground to inspect buildings etc., without the use of a plastic or other barrier, playing in outdoor sandboxes that are accessible to wildlife or stray cats.
Hookworm infections in people and dogs
Hookworms are not known to be transmitted by time spent next to your dog or by your dog licking you . Most human infections are due to time spent in direct contact with soil or spending time in sandboxes that are not protected from animal waste. Hookworms can infect people, mostly by direct penetration into the skin.
The condition is called cutaneous larva migrans and causes a very itchy serpentine rash. The infection will not last long and will typically regress on it’s own.
Roundworm infections in people and dogs
Roundworm infections can have devastating effects on people. Human cases are most common in children that have pica and eat dirt. Some cases occur in children that have close associations with untreated free roaming and breeding dogs. Most adults infected with roundworms are asymptomatic.
Roundworm can affect organs in the body like the liver, the lungs and even the nervous system. An ocular form of roundworm infection can cause severe retinal changes and vision changes. There should be no transmission from a dog who receives a monthly heartworm prevention with a dewormer added.
Human cases are most common in children that have pica and eat dirt. Some cases occur in children that have close associations with untreated free roaming and breeding dogs. Most adults infected with roundworms are asymptomatic.
Tapeworm infections in people and dogs
It is very rare for people to be infected with dipylidium caninum, the most common tapeworm of dogs. Very rarely a child can contract this by ingestion of a flea. Their symptoms are still generally mild and readily treated.
The more serious but rare tapeworm species, echinococcus, can cause severe disease in humans. However, the risk is still very low to contract this disease. The disease is contracted by consuming eggs shed in the stool of a dog that is infected. Dogs must prey on wildlife (ususally dogs that eat infected rodents) to be infected with this tapeworm. Dogs that take a monthly heartworm prevention with praziquantel added should be protected. See the chart above for examples of these heartworm products with efficacy against tapeworm.
What home remedy can I use to deworm my dog
If you see worms in your dog’s stool or vomit and your dog is on a heartworm preventative that is marketed for roundworm and hookworm prevention: your dog most likely has a tapeworm infection. Praziquantal is the preferred treatment for tapeworm and requires a prescription from your veterinarian.
If your dog has a roundworm infection, you can purchase pyrantel over the counter to treat this infection. Pyrantel also treats for hookworm infections.
Fenbendazole is a good broad spectrum dewormer available over the counter. This does not treat the most common tapeworms in dogs. However, it will treat roundworm, hookworm, whipworms, lungworms and giardia infections in dogs.
Conclusion for worms in dogs:
Most adult dogs that have diarrhea are not diagnosed with worms. The cause of their diarrhea is most often not identified, but chalked up to “dietary indiscretion” or stress such as boarding.
In puppies, worm infections are far more common and expected. Puppies that receive basic deworming care typically won’t develop the more serious and severe symptoms of worms.
Most heartworm medications are designed to also act as a monthly dewormer to treat dogs for worms that they are likely to encounter in everyday life as they explore the world by licking, chewing and digging.