How to Treat Pinworms in Mice

Two Parts:Seeking Veterinary TreatmentCleaning Your Mouse’s Cage

Pinworms are tiny worms that live in a mouse's large intestine. Pinworm infections are common in mice and occur when a mouse eats pinworm eggs by accident. Pinworms usually do not make mice very sick. In fact, you may not even notice a pinworm infection in your mouse until it has a heavy worm burden.[1] If your mouse has pinworms, treatment will involve killing the worms with medication and cleaning your mouse’s cage.[2]

Part 1
Seeking Veterinary Treatment

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    Take your mouse to your vet. A pinworm infection requires veterinary treatment, even if your mouse doesn’t look very sick. Your vet will prescribe an anthelmintic, which is a medication that kills intestinal worms. Ivermectin and fenbendazole are the main anthelmintics used to treat pinworms in mice.[3]
    • Before prescribing the medication, your vet will confirm that your mouse has pinworms.
    • To identify pinworms, your vet can examine a liquid solution of your mouse’s feces (‘fecal float’) with a microscope. They can also stick a piece of clear tape to your mouse’s rear end and examine the tape with a microscope.[4]
    • Two species of pinworms affect mice.[5] They are treated in the same way.
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    Give your mouse oral ivermectin. If your vet prescribes ivermectin, you will give your mouse 2 treatments by mouth, 10 days apart: give your mouse the first treatment, then give the second one 10 days later.[6] You could also add ivermectin to your mouse’s drinking water, but this would require changing the water every day, which may be time consuming.[7]
    • Oral ivermectin will be a liquid solution that you will administer with a syringe (without the needle).
    • To give your mouse oral ivermectin, pick up your mouse by the base of its tail and place it in the palm of your hand, with its back against your palm. Gently scruff your mouse by the neck, place the syringe of ivermectin in the mouth, and slowly dispense the medication.[8]
    • Ivermectin can be applied directly to your mouse’s anal region with a spray bottle.[9] This may be a little tricky to perform, though, so your vet will probably prescribe the oral formulation.
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    Treat your mouse with fenbendazole. Medicated diets containing fenbendazole can also treat pinworms.[10] If your vet recommends the therapeutic diet, you would feed it in a ‘one week on, one week off’ schedule for as long as your vet prescribes.[11] During the off weeks, you would feed your mouse its regular diet.
    • Purchase the diet through your vet.
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    Monitor your mouse for side effects. Ivermectin can cause serious neurologic problems. It can cross the ‘blood brain barrier,’ which is in place to prevent certain drugs from entering the brain. If ivermectin enters the brain, it can cause such side effects as coma, depression, and sudden death.[12] If your mouse seems really sad (no energy, not eating much, not playful) or looks unconscious, tell your vet right away.
    • Ivermectin side effects are more common in newborn mice.[13]
    • Fenbendazole usually does not cause serious side effects in mice.[14]

Part 2
Cleaning Your Mouse’s Cage

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    Clean the cage regularly. Pinworm medication will kill the adult worms inside your mouse, but not the eggs. The eggs can actually go airborne, so they could be anywhere in your mouse’s cage, even though you won’t be able to see them. Therefore, cleaning your mouse’s cage is a very important aspect of pinworm treatment in mice.[15] Clean the cage at least once a week.[16]
    • Male mice leave their scents in their cages. Frequent cleaning would remove that scent and cause the mice to ‘mark’ the cage even more, making the cage quite smelly. If you have a male mouse, prevent excessive marking by rotating when you replace the bedding and litter.[17]
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    Take everything out of the cage. First, move your mouse to a separate cage by gently picking it up by the base of its tail and sliding your other hand under its body.[18] Slowly lower your mouse into the other cage. Next, remove the bedding and litter and take out all cage accessories (toys, food bowl, water bottle).
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    Clean and sanitize the inside of the cage. Cleaning the cage will remove the dirt and sanitizing will kill the pinworm eggs. Use hot and soapy water, along with a sponge or scrub brush, to clean the cage. Rinse out all of the soap before sanitizing. To sanitize, spray a bleach solution (1/2 tablespoon bleach/1 gallon water) throughout the cage. Let the bleach solution dry on its own—do not rinse it off.[19]
    • Unfortunately, pinworm eggs are resistant to many types of disinfectants.[20] However, bleach is recommended for killing pinworm eggs.
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    Clean and sanitize the cage accessories. Use 3 buckets to clean and sanitize the cage accessories. Fill the first bucket with hot, soapy water and clean the accessories. Fill the second bucket with hot water to rinse off the accessories. Fill the third bucket with a cold bleach solution (1/2 tablespoon bleach/1 gallon water) and let the accessories soak for about 30 seconds. Let the items air dry before putting them back in the cage.[21]
    • A toothbrush may help clean the edges or hard-to-reach spots of the accessories.[22]


  • Pinworms are commensal, meaning they don’t harm or benefit to the host.[23] However, a heavy pinworm burden could cause irritation in the anal area.[24]
  • Adult pinworms look like long, white tubes. They are a few millimeters long. Pinworm eggs are too small to see without a microscope.[25]
  • Pinworms affect male mice more than female mice. Also, young mice are more affected than older mice.[26]
  • Transmission of pinworms from mice to people is unlikely. Even still, you should wash your hands before and after handling your mouse.[27]
  • Consider having your vet occasionally test your mouse’s feces for pinworms.[28]


  • It can be difficult to kill all pinworm adults and eggs with treatment.[29]

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Categories: Mice and Rats