How Do Dewormers Work?

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Intestinal worms are common in pets, and most puppies and kittens are actually born with them. Fortunately, they are easily treated with deworming medicine for puppies and kittens. There are many different dewormers, and each treats certain types of worms. If you notice symptoms of worms in your pet, be sure to take her to the vet for a diagnosis and treatment.


Each dewormer treats certain types of worms.
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Parasites in pets

There are a few common intestinal worms that may infect your pet, including hookworms, roundworms, tapeworms, and whipworms. Diagnosis is usually done by a stool test.


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Hookworms can be passed from mother to puppy and transmitted through feces. Hookworms feed on the animal's blood and can be fatal for puppies, so prompt treatment is required. Infected animals may be malnourished, weak, and fatigued. Roundworms are commonly passed to puppies from the mother, and pets can also get it by eating infected feces. Symptoms of roundworms include a potbelly, weight loss, belly pain, vomiting, diarrhea, and a dull coat, and you may see worms in your pet's stool.


Tapeworms are generally acquired from infected feces or fleas. They often look like small grains of rice in your pet's stool or around his anus. Other symptoms may include weight loss, itching and licking around the anus, diarrhea, and irritability. Whipworms also feed on your pet's blood. Your pet may pick up this parasite from the soil while he is outside playing. Common symptoms include anemia, bloody diarrhea, dehydration, and weight loss.


Dewormer for dogs and cats

There are many types of dewormers that target different worms. This is why it is important to consult your veterinarian to confirm what type of parasite is affecting your pet. Your vet will recommend a dewormer, or if you purchase one on your own, make sure it is labeled for the specific worm and for the type of pet since not all dog medications are safe for cats and vice versa.


Consult your veterinarian for the right dewormer.
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The most common way that these medications work is to affect the central nervous system of the worm. This prevents the worm from attaching to the intestines and allows the worm to be passed out of the system with the pet's stools. Some tapeworm medications work slightly differently and cause the worm to dissolve.



Many dewormers only work on mature worms, while others target worm eggs or larvae. This means that multiple treatments may be necessary to fully deworm your pet. Follow the instructions from your veterinarian and on the product label.

Potential side effects

After deworming, it is perfectly normal to see worms in your dog's feces. Minor digestive upset, including diarrhea, is also normal for a couple of days after deworming. It is rare for dogs to have a serious reaction to a dewormer, but there are some potential side effects when you administer dewormer for dogs or cats for which you need to watch out.


After deworming, it is normal to see worms in your dog's feces.
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If diarrhea worsens, is bloody, or continues after about three days, follow up with your veterinarian. Other causes for concern include repeated vomiting and a loss of appetite that lasts for more than two days. If your dog experiences difficulty breathing, lack of coordination, or trembling after deworming, consider this an emergency and get your dog to the vet right away.



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