Capillariasis is a condition in which parasitic worms from the Capillaria genus, commonly referred to as hairworms, infest a cat or other animal’s bladder and urinary tract. Cats, other companion animals, and wild animals can all be infested by ingesting the eggs or intermediate hosts of the Capillaria worm. Once the worms, larvae, or eggs have been ingested, they move through the cat’s system and make their home in the bladder. They can also be found in the intestinal tract, urinary tract, the ureter, and the renal pelvis. The infestation can cause symptoms similar to that of a urinary tract infection, but may not cause any signs or require any treatment.

Many cats with capillariasis will not have any obvious symptoms or signs of infestation. In small amounts, the worms do not do much damage or cause many side effects. Cats with a more severe infestation may have symptoms similar to that of a urinary tract infection. 

Symptoms Include:

Types

There are several types of Capillaria worm that can infest companion animals like cats and dogs. Not all types live and breed in the same location within your pet. For example, Capillaria boehmi lives in the nasal mucosa and sinuses, causing sinus and allergy symptoms. 

Types of Capillaria that cause capillariasis include:

Host animals can be infected in various ways depending on the type of hairworm. Some Capillaria species require an intermediate host as part of their lifecycle. This means that the worm’s eggs are not themselves infectious. In these cases, eggs are passed through the urine or feces of an infected animal. They are then consumed by earthworms, where they move into the next stage of their lifecycle. They infest their final host when an animal eats the earthworm. For other types of hairworm, the eggs do not require the intermediate host, and cats can become infested after eating or drinking something contaminated with the eggs.

Since few symptoms may be present in a cat with capillariasis, a diagnosis is often made when the pet is being treated for something else. The clinical signs your veterinarian will look for to aid in making a diagnosis include bladder condition, urine color, and the presence of eggs in the urine. Be prepared to discuss your cat’s medical history and eating habits. If you have been observing signs of bladder or urinary tract issues in your pet, be sure to make the veterinarian aware. A urine sample will be required to confirm the diagnosis. Capillaria worm eggs can be seen in urine under a low magnification. They are oval shaped with plugs at each end. Visual confirmation of eggs in the urine is all that is necessary to diagnose capillariasis. This can be difficult, however, because eggs are not always present in the urine. It is possible for a cat with bladder worms to be negative for eggs in their urine.

Capillariasis is not considered life-threatening. Most cats with the condition will go undiagnosed and not require any treatment. If your pet has been diagnosed, this means a larger concentration of the hairworms is present in their bladder and urinary systems. Your veterinarian will administer a treatment designed to kill the adult bladder worms. Treatments may include:

Most animals will make a full recovery from capillariasis. Even without treatment, the prognosis is good. Many cats live with the infestation and never have any symptoms of concerns. Be sure to follow your veterinarian’s instructions for medications and follow-up appointments. Your cat will need to be tested after the antiparasitic treatment to ensure the worms are no longer present. Monitor your pet closely to make sure they are eating and drinking enough while they recover. You may also want to clean food and water dishes and litter boxes thoroughly to remove any eggs.