The nematode Capillaria plica occurs in the urinary bladder of dogs, free-ranging carnivores, and rarely cats, worldwide, likely including Canada.

The adults are very slender, with males measuring 13-30mm in length and females 30-60mm. The eggs of C. plica (shed in urine) are barrel shaped and colourless with a thick striated shell and bipolar plugs. Capillaria plica has an indirect life cycle, involving an earthworm intermediate host.  Eggs are shed in urine of the carnivore definitive host and a first-stage larva develops within the egg in about 30 days.  When ingested by an earthworm, the egg hatches to release an infective first-stage larva. After the definitive host ingests the infected earthworm, the first-stage larva migrates through the intestinal wall to the bloodstream, then to the kidney, ureters and finally to the bladder where it embeds in the mucosa, matures into an adult, reproduces and sheds eggs through the urine. The pre-patent period is approximately 8 weeks. Most infected dogs and cats are asymptomatic. Heavy burdens of C. plica can occasionally cause cystitis, hematuria, dysuria, pollakiuria (frequent urination), urethral obstruction, renal failure, or lead to secondary bacterial infections. Symptoms are more severe with pre-existing renal disease. Diagnosis is typically made by identification of C. plica eggs from urine sediment in a urinalysis. Medical imaging of the bladder and/or cystoscopy may also be helpful.   If treatment is necessary, dogs infected with C. plica may require repeat treatments. No products are labelled for this parasite within Canada but, fenbendazole and macrocyclic lactones, especially the newer products (moxidectin, milbemycin) should be effective. 

This parasite is not thought to have zoonotic significance.