How to diagnose and control a worm infestation in your dog

By The To 18:01

Dog worms are fascinating yet dangerous and somewhat disgusting creatures that put your dog and yourself at risk to contract mild to fatal diseases. 


You’ve learned in our last article 'Why you should worry about dog worms' what these worms are, and how they can harm you and your dog. You now are wondering what you can do to fight them. Unfortunately, there is no way you can completely get rid of them. You are always exposed to some level of risk, but you can reduce it. The key is to find the right treatment adapted to your situation and take some preventative hygienic measures.


Let’s see how.


How do I know my dog has worms?

This is a general recommendation to regularly look for the worms that may parasite your dogs.  The Companion Animal Parasite Council recommends performing a control 4 times a year. On practice this is rarely achieved. 

The flotation technique

The mainstay of worm diagnosis is fecal flotation and centrifugation technique. The goal is to detect nematodes eggs or flatworms segments in the feces. 

Toxocara canis

Typically, your vet will mix your dog’s feces that you will have previously collected in a solution. After centrifugation, they will then sample the supernatant, supposed to contain worm eggs and put it under a microscope. They will see and recognize the different types of egg or segment.


This examination tells you when your dog has worms. But it does not guarantee you your dog doesn’t have worms when the results are negative. Why? Not because your vet has done a bad job. That’s because worms do not shed eggs all the time: they can be present and not be detected by fecal matter examination.


Nematodes lay tens of thousands of eggs daily, but only 15 days after they’ve reached the digestive tract. Flatworms shed segments episodically. Absence of segments does not mean there is no worm. 

The case of heartworm

As a heartworm never gets in the digestive tract, there is no chance of finding eggs in the feces.  Infection in dogs with heartworms can be diagnosed with various  microfilariae antigen detection tests or by directly finding microfilariae in blood.


If tests are positive, and if your dog shows up symptom suggesting the presence of adult worms, your vet will perform radiographic and/or echocardiographic examinations.

How should I control my dog’s worms?

Your vet may prescribe you a deworming treatment without having made a fecal examination. Rather than identifying the worms that are present, they will assess the risk your dog runs to harbor worms or to be infested in the near future.


There are some general principles that help you understand their prescription and ask them the relevant questions.

Dewormers only treat worms that are present

Keep in mind that there is no delayed effect for any wormer as there is for instance in anti-flea or anti-tick products.

You will only get rid of worms that are infecting your dog and not prevent any further infestation, even on the following day. No prevention is possible.

As a consequence, there is no way to get your dog 100% worm free all the time.

No dewormer is effective on all worms

There are many good wormers on the market. Unfortunately none of them will control all the worms we have been discussing here.


For instance, the active ingredient milbemycine oxime is not effective against Uncinaria. Ivermectin is not effective against whipworms or the widely used combination febantel+pyrantel+praziquantel has no efficacy against heartworms.


Try focus on the most important worms

That is to say those which are dangerous for public health and your dog. Echinococcus and heartworms are deadly respectively for humans and dogs. Toxocara and Ancylostoma are frequent worms that may also cause your dog’s death.


Think about the other parasites

Some products are effective both against some worms and some external parasites. If your dog has mites or fleas, choose a product that could also help control them.


Adapt to the situation

If you’re sure that your dog doesn’t hunt preys or eat raw food, there is very little chance that they may get a flatworm. If your bitch is pregnant, or in heat, the roundworms and hookworms larvae encysted in her tissues may well wake up and resume their journey to the digestive tract, lay egg, contaminate the environment and infect her puppies.

If you’re running a kennel, think about whipworms and regularly ask your vet to diagnose for them. If your dog doesn’t have fleas, they should not have Dipylidium either. If the winter is cold, there is little chance that mosquitoes will continue to bite your dog.

Running in the grass yard@Affectionate Pet Care

Think local

The risk your dog runs is closely linked to the place where you live.  The Companion Animal Parasite Council (CAPC) has published a series of maps that indicate the prevalence or parasites in any US county. Find them here: https://www.capcvet.org/parasite-prevalence-maps/


Limit environment contamination with parasites

You understand now that your dog may become a contaminating agent for worm eggs. These eggs can in turn contaminate humans and animals in the neighborhood.  It is your responsibility, as a citizen, to contribute to limiting the risk of contamination. In addition to treating your dog against worm you will have to take some measures:

  • Pick up fecal matter
  • Do not touch fecal matter with your bare hands and wash your hands
  • Do not let your dog hunt prey
  • Do not feed your dog uncooked meat
  • Protect your dog against mosquitoes and fleas


You’ve seen there is no way to be 100% sure that your dog as no worms. Likewise, there is no treatment that prevents your dog from being infected with worms.


This leaves us with a well educated guess based on the risk your dog harbors or will harbor dangerous worms and on the cost involved in implementing an optimal control.


Seek advice at the vet clinic. They will take the time to inform you about the products and the treatment strategies adapted to your situation.


Gilles Ventejol manages the team working for AnimalPatient.com. He has a comprehensive experience of more than 20 years in the animal health industry marketing, and has written dozens and dozens of information materials for vets and owners: brochures, guides, leaflets, videos and of course websites.
You can contact him at https://animalpatient.com/.

Take care…

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