deworming puppy

What To Expect After Deworming Your Puppy

Most dogs probably have a few parasites floating around in their digestive tracts, but the immune systems of mature dogs are typically able to keep the invaders in check.

Puppies, on the other hand, can quickly become overwhelmed and develop a belly full of wriggling worms.

These worms can actually cause quite a few health problems for puppies. They are, quite literally, stealing some of the calories, vitamins and minerals your young pup consumes. They can also cause terrible intestinal issues, lead to secondary infections and generally make your puppy feel horrible.

Worms and other parasites are also quite contagious, and puppies can pass them between each other several different times. Fortunately, most common puppy worms are easy to eradicate, and they rarely cause serious problems if treated in a timely fashion. 

But the deworming process, as it is often called, can present a few surprises for first-time dog owners. We’ll explain some of the side effects of deworming puppies below, but let’s review some puppy deworming basics first.

Types of Parasites that Afflict Puppies

Although owners and vets often refer to parasitized puppies as having “worms,” there are several different types of parasites that can afflict dogs. Coccidia, for example, are single-celled protozoans that are not worms at all.

There are also several different types of parasitic worm. Tapeworms belong to a group of organisms called flatworms, while roundworms, hookworms and whipworms are all members of the same group.

Some of the most common types of parasites that afflict puppies include:

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Collectively, these parasites exhibit different life histories and harm dogs in different ways.

Fortunately, there are several broad-spectrum wormers available, which will eliminate several different types of worms, protozoans and other parasites. 

These types of medications will make it easier to treat your dog and help him feel better as quickly as possible. Check out our review of the Best Dog Dewormers for Big Dogs to find some of the best options on the market. 

Just be sure to keep your vet in the loop when deworming your puppy, and always follow the directions on the package explicitly. 

deworming puppy

Photo from the CDC.

The Parasite Life Cycle

As mentioned earlier, different worms have different lifecycles, but most of those who target dogs have what is known as a direct life cycle. This means that they do not require an intermediate host to infect a dog (although a few canine worms, such as tapeworms, do have indirect lifecycles and must pass through another species before causing problems for your dog).

Parasites with direct lifecycles can exhibit explosive population growth in a very short period of time. Most organisms with direct lifecycles live as adults in a puppy’s digestive tract. While inside your puppy, they absorb nutrients from your pup’s intestines and shed eggs (or spores) that exit the dog’s body during elimination.

Any dog that comes into contact with these microscopic eggs may inadvertently swallow a few, which will ultimately hatch and mature inside your dog’s digestive system.

What to Expect After Deworming a Puppy

Normally, there are not many visible signs that directly indicate the presence of worms or other parasites. Your dog may vomit, suffer from diarrhea, drag his rear end on the carpet or show disinterest in his food, but you won’t see anything unusual, as parasite eggs are not often visible to the naked eye.

However, when you give your dog a deworming medication, the adult worms and protozoans living in your dog’s intestines are killed. This causes them to release their grip on your puppy’s intestinal tract, and they’re ultimately expelled via the anus.

This side effect of deworming a puppy can be a bit startling. Adult protozoans are not visible to the naked eye, but most adult worms are visible – many look like long strands of very thin pasta.

Sometimes these dead parasites are expelled during defecation, but they can also be seen emerging from a puppy’s anus when he is not defecating. Sometimes, the worms will still be in the process of dying, which means they’ll be crawling around when you see them.

This can obviously be quite unsettling for owners who aren’t expecting such a ghastly sight, but it is completely normal and of no cause for concern.

There are a few other common side effects that often occur when you deworm a puppy. For example, your pup may also suffer from minor intestinal issues, including diarrhea, but this should pass within a few days.

Some puppies may also act a little different for a few days while their body eliminates the worms, but as long as they return to normal and resume typical elimination habits within about three days, there’s no reason to worry about these types of deworming side effects.

If you’d like to see a puppy eliminating a rather significant quantity of large worms, watch this video

Caution: While extremely educational, this video may be very disturbing to some viewers. 

Symptoms of Concern: When to Contact Your Vet

If you’ve selected an appropriate deworming medication for your puppy and administered it in accordance with the product's instructions, you shouldn’t have to worry about many problems.

However, although they are rare, serious side effects of deworming a puppy that can occur in a small number of dogs. If your dog exhibits blood in his stool, ongoing diarrhea (that lasts longer than three days), vomits more than once or appears disinterested in food for more than a day or two, contact your vet.

Of course, serious symptoms – trembling, uncoordinated behaviors, extreme lethargy, breathing difficulties and similar signs – should always trigger an immediate trip to the vet, but such symptoms are extremely rare.


Photo from Wikipedia.

Deworming a puppy is a pretty simple task, and it will greatly improve your puppy’s chances of thriving. But you’ll want to select a good medication for your pet and make sure that you follow the administration instructions to the letter.

With a little luck, your puppy will remain worm-free and you can stop looking at worms crawling around in his poop.

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