Understanding Bladder Worms in Cats
Bladder worms in cats refer to small parasitic worms, most commonly Capillaria plica (also known as Pearsonema plica) and Capillaria feliscati (Pearsonema feliscati), that take up residence in the bladder wall or sometimes the kidneys and other parts of a cat's urinary tract. While these infections are rare, they can cause discomfort and health problems when present in large numbers.
What Are Bladder Worms?
The term "bladder worm" describes these Capillaria species because they specifically target the bladder. They may also be found in the kidneys or elsewhere along the urinary tract. Most infected cats show no obvious signs, but a heavy infestation can create significant inflammation and lead to a range of urinary symptoms.
Life Cycle and Transmission
The life cycle of Capillaria is fascinating—and a bit convoluted. After maturing within a cat's bladder, adult worms release eggs into the urine. These eggs don't infect cats directly; instead, they must be eaten by earthworms first. Inside the earthworm, the parasite develops into its infectious stage. Cats become infected by:
- Eating earthworms directly
- Ingesting soil or material contaminated with earthworm debris
- Consuming animals that have eaten earthworms
This means indoor cats are at much lower risk compared to outdoor hunters who might snack on earthworms or prey animals.
Other Capillaria Species
Not all Capillaria species stick to the bladder. For example:
- Eucoleus aerophilus: Infects the respiratory tract, laying eggs in airways that are coughed up, swallowed, and passed out in feces.
- E. boehmi: Can infect sinuses and nasal passages.
Clinical Signs: What to Watch For
The majority of cats with Capillaria infection show no symptoms at all. When problems do arise, they're usually related to where the worms have settled:
- Bladder/urinary tract (P. plica, P. feliscati):
- Blood in urine (hematuria)
- Urinating outside the litter box (accidents)
- Straining or discomfort while urinating
- Painful abdomen or fever (rare)
- Licking genital area excessively
- Incontinence or leakage (rare)
- Respiratory tract (E. aerophilus):
- Coughing or wheezing
- Trouble breathing
- Nasal/sinus infection (E. boehmi):
- Sneezing or nasal discharge
A number of other conditions—like urinary tract infections or bladder stones—can produce similar symptoms, so it's important for veterinarians to consider all possibilities.
Diagnosis: How Are Bladder Worms Found?
The most common way to diagnose Capillaria infection is through urinalysis. A vet will examine urine sediment under a microscope looking for characteristic eggs: oval-shaped, colorless with thick shells and bipolar plugs at each end.
The catch? These eggs aren't always shed consistently, so sometimes multiple urine samples are needed for an accurate diagnosis. If there's suspicion of respiratory involvement, fecal exams and chest X-rays may help; bronchoscopy or bronchoalveolar lavage can also be useful for lung cases.
Treatment Options for Infected Cats
Mild infestations without symptoms usually don't require treatment. But if your cat shows clinical signs—or if egg shedding persists—veterinarians may prescribe antiparasitic medications such as:
- Fenbendazole: Often given orally at 50 mg/kg for 4–10 days.
- Ivermectin: Typically injected at 0.2 mg/kg.
A few doses may be needed to fully clear the infection. If there's significant inflammation or discomfort, supportive care—like anti-inflammatory drugs—might be recommended as well. Currently there aren't any products specifically labeled for treating Capillaria in cats; vets use these medications off-label based on experience and evidence.
Prognosis and Recovery: What Should You Expect?
The outlook for most infected cats is excellent with proper treatment—most recover fully once antiparasitic medication has done its job. Follow-up testing is wise to ensure all worms have been eliminated from your pet's system.
If your cat isn't showing any symptoms but tests positive for Capillaria eggs repeatedly, your vet might still recommend treatment just to prevent future problems.
Prevention: Keeping Your Cat Safe from Bladder Worms
The best way to prevent Capillaria infection is by stopping exposure to their intermediate host—the humble earthworm! Here’s how you can reduce your cat’s risk:
- Keep cats indoors whenever possible.
- Avoid letting them hunt small animals that might eat earthworms.
- If you have an outdoor cat, regular deworming may be advised by your vet.
- A clean living space with fresh water helps minimize environmental risks.
You don't need to worry about catching these specific parasites from your pet; they're not considered a direct public health concern for people.
A Few Extra Notes About Bladder Worms in Cats
You’re more likely to find Capillaria infections among wild carnivores like foxes and raccoons—they act as reservoirs for these parasites. Any age cat can get infected but it’s most often spotted in adults during routine checks for unrelated urinary issues (sometimes it’s just an incidental finding). Luckily, most infections stay subclinical—serious disease from heavy infestations is quite rare!
