Reasons why you might see worms despite worming
You gave your pet their regular wormer, so everything is good right? You took your dog out and there it was. The worm. Your cat came to curl up next to you and there was a little grain of rice and it was moving. We get questions about sources of parasites in pets regularly. Occasionally we’ll get questions from pet owners who are using parasite prevention but unfortunately still find worms from their pet. Albeit less common, we encourage people to have faith and go over these reasons why you might be seeing breakthrough parasites in your pet.
They didn’t actually eat the wormer.
- Some pet parents put their wormer tablet directly into their pet’s food and walk away to do other things, especially dog owners. This works great for good eaters like my goofy golden retrievers, but the pickier pets will sneak around that tablet like they’re Gordon Ramsey judging a food competition. You need to ensure your pet consumes the wormer. We know this may seem silly but pets can find all sorts of ways to get around eating pills, even when hidden in the best treats!
Your pet is exposed to heavier levels of parasites on a regular basis.
- Pets that are often in the following scenarios have a much higher potential of parasite exposure/infection: dog parks, dog daycares, group play boarding facilities, training events, flat/rental properties with common pet relief areas, areas with heavy wildlife populations (many can carry parasites), neighborhoods with high numbers of outdoor cats, pets that like to hunt (cats for rodents/birds) etc. More animal exposure means more opportunities for potential infection.
You are not worming regularly.
- Worming 1-2 times per year is not enough to keep parasites away. Many of our common parasites have life cycles that are completed in as little as a few weeks up to 2-3 months. Because of this, wormers are often recommended to be administered monthly to every 3 months to break the life cycle of the parasite if your pet has become infected. Checking with a vet to ensure you are using the right product for your pet and are treating frequently enough is a must!
The wormer you are using does not cover the type of parasite your pet contracted.
- There is not ONE wormer that protects or treats ALL types of parasites. We wish there was, however this makes appropriate and targeted worming for your pets lifestyle all the more important. Most of the common wormers on the market will prevent the major culprits including roundworms and hookworms, however not all products will also cover additional parasites like tapeworm or lungworms. Again, being aware of WHAT your wormer covers is important and can be discussed with a vet. There are some parasites out there that are not covered by common wormers and require a more specific treatment from a vet. For this reason, faecal testing is essential so we know what parasite is actually present. Side note – don’t forget many intestinal parasites are microscopic, so regular worming along with faecal checks at the vet are recommended.
- Common scenario: Pet owner giving cat a wormer that only treats roundworms and hookworms and cat becomes infected with tapeworms (contracted from eating a dead rodent), much to the owners dismay and frustration. The first assumption is the product does not work, when in reality the product is not a drug that treats tapeworms!
Your wormer works great, but your pet was infected in between doses.
- It’s important to make a distinction between wormers vs. flea/tick preventatives. Wormers are not preventing EXPOSURE to the parasite, but rather stopping the life cycle/killing off the parasite upon administration. Wormers do not remain in the system persay between doses to prevent infection like flea and tick monthly preventatives do. The hope is that regular targeted worming stops development of specific parasites and is given at appropriate intervals so that these parasites do not have the opportunity to grow into adults then shed eggs to infect other pets. Rarely pets, particularly those with higher exposure risk, will manage to pass an adult in between doses which may indicate a need for a change in worming frequency. Also note, pets may pass dead worms as well.
These are important considerations we like to cover with pet owners when they ask questions about wormers, their efficacy, and how they work. The wormers used in the veterinary community are extremely safe and effective products. We would say by far the most common reasons for people to have issues is they don’t realize what their wormer actually protects against or are not giving it at appropriate intervals! That’s what vets are here for, to be the reliable source of this information and make guided recommendations for what is best for your pet based on their needs.
Dr. Kirsten Ronngren, DVM MRCVS
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