Bladder Worms in Cats

Bladder worms are small, hair-like worms that infect a wide range of hosts. The worms attach to, or bury themselves into the bladder mucosa and sometimes in the pelvis of the kidney or urethra of the host where they cause mild inflammation. Adult males are 13-30 mm and females are 30-60 mm long.

Capillariasis is the name of bladder worm infection.

There are two species of bladder worms that can infect cats.

  • Capillaria feliscati
  • Capillaria plica

Cats, dogs, wild canids (foxes, coyotes, wolves) and mustelids (weasels, badgers, stoat) can all become infected with this parasitic worm although infection in dogs and cats is rare.

The distribution of both Capillaria feliscati and Capillaria plica is worldwide.


Adult worms embed in the mucosa lining of the bladder where they release eggs approximately 60 days after infection. The eggs are passed into the environment via the host urine but are not immediately infectious. Once in the environment the eggs embryonate, at which time they become infectious.

Earthworms are thought to be a secondary host, the earthworm ingests the infectious worm eggs which then develop into infective larvae. When the earthworm is eaten, the larvae leave the earthworm in the intestine, moults and invades the intestinal wall where it undergoes another moult. From there it then makes its way to the bladder via the circulatory system where they moult into adult worms. Infection may also occur if the cat comes into direct contact with infectious larvae which is accidentally ingested when the cat grooms.

Clinical signs

Most infected cats show no clinical signs unless there is a heavy worm burden that causes inflammation or if worms lodge in the ureter or renal pelvis. Cats with a heavy worm burden may display signs of urinary tract disease.


Diagnosis is often incidental during routine analysis of the urine where eggs may be found in the urinary sediment.

When symptoms do present, such as cystitis or difficulty urinating, the veterinarian will perform a complete physical examination of your cat. During the examination, the cat’s bladder may be distended and painful if a full or partial blockage has occurred.


In severe cases where your cat is unable to urinate, a catheter will be necessary to empty the bladder of urine.

Antibiotics and corticosteroids to treat inflammation and bacterial infection.

Fenbendazole, levamisole, and ivermectin are all anti-parasitic treatments that can kill the worms.

If no symptoms are present, your veterinarian may opt to not treat the worms at all.

A follow-up appointment will be required to check the urine for eggs. If so, it will be necessary to re-treat.


The only way to prevent bladder worms is to keep your cat indoors so that he can not hunt.


  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio

    View all posts