Bladder Worms in Cats – Symptoms, Diagnosis & Treatment


Bladder worms in cats

Bladder worms are small, hair-like worms which are between 16-50 mm long. The worms attach to, or bury themselves into the bladder mucosa and sometimes in the pelvis of the kidney or urethra of the host.  Capillariasis is the name of bladder worm infection.

There are two species of bladder worms which 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.

How do cats become infected?

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 cat’s urine but are not immediately infectious. Once in the environment the eggs embryonate, at which time they become infectious.

Earthworms may be a possible intermediate host, ingesting 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.

There appear to be differing opinions as to how cats become infected. It may be via direct ingestion of an infected earthworm or ingestion of an infected transport host such as a bird who has eaten an infected worm.


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, your veterinarian will perform a complete physical examination of your cat. During the examination, the cat’s bladder may distended and painful if a full or partial blockage has occurred. 


Most cats are asymptomatic unless there is a heavy worm burden which causes inflammation or if worms are in the ureter or renal pelvis.  When symptoms do develop, they include: 

  • Cystitis (inflammation of the bladder)
  • Blood in the urine (hematuria)
  • Frequent urination (pollakiuria)
  • Difficulty urinating (dysuria)

Other symptoms may include:


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 which 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.