Bladder Worms in Cats

bladder worms in catsBladder worms are small, hair-like worms (they are known as hairworms) which are between 16-50 mm in length, females are larger than males. The worms attach to, or bury themselves into the bladder mucosa and sometimes in the pelvis of the kidney or urethra of the host. Infection is known as capillariasis.




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?

The exact life cycle of these worms still isn’t completely understood. 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.

It is believed earthworms may be an 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 the 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 consumed an infected worm.

How are bladder worms diagnosed?

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 be found to be distended and painful if a full or partial blockage has occurred.

What are the symptoms of bladder worms in cats?

Most cats won’t display obvious signs of infection unless there is a heavy worm burden resulting in inflammation or when the worms are located in the ureter (the duct which passes from the kidney to the bladder) or renal pelvis. When symptoms do present, they may be as follows:




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

Other symptoms may include:

  • Abdominal pain
  • Urinary blockage
  • Fever

How are bladder worms treated?

In severe cases where your cat us unable to urinate, a catheter may be inserted to void the bladder of urine. Antibiotics and corticosteroids may be prescribed to treat inflammation and bacterial infection. Worms can be killed with one of several anti-parasitic medications such as fenbendazole, levamisole and ivermectin.

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

Your veterinarian may require a follow-up appointment to determine if eggs are still present in the urine, if so, re-treatment with an anti-parasitic medication may be required.

Preventing bladder worms

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




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