Hi stranger! Signing up for MypetMD is easy, free and puts the most relevant content at your fingertips.

Get Instant Access To

  • 24/7 alerts for pet-related recalls

  • Your own library of articles, blogs, and favorite pet names

  • Tools designed to keep your pets happy and healthy

or Connect with Facebook

By joining petMD, you agree to the Privacy Policy.

Bladder Threadworm in Rats

Urinary Nematodiasis in Rats


A common urinary disease in rat colonies is nematodiasis. This occurs when the nematode parasite Trichosomoides crassicauda infects the rat's urinary bladder, causing painful urination, stunted development, and stones in the bladder (bladder calculi). Kidney diseases like pyelitis, renal pelvic inflammation and stones in the kidney (uroliths) may also occur if the parasite (threadworm) moves upward toward the bladder.


The source of infection is contact with Trichosomoides crassicauda eggs that have been passed in the urine of infected rats. Typically, nematodiasis occurs in rats older than two to three months and is resolved with the insecticide ivermectin. Reinfection can be prevented by maintaining hygienic living conditions with proper sanitation.


Symptoms and Types


  • Painful urination (dysuria)
  • Stones in the bladder and/or kidneys
  • Failure to develop properly
  • Sudden or chronic renal pyelitis
  • Renal pelvic inflammation
  • Bloody urine due to stone formation


The male threadworm attaches itself to the lumen of the rat’s bladder and the female threadworm attaches itself to the lumen and mucus membrane of the bladder. The male threadworm can sometimes even live insides the uterus of the female threadworm. The male threadworms grow to be 1.5 to 2.5 millimeters in length, while the female threadworm can be as long as 10 millimeters (1 centimeter).




  • Infection with the threadworm, Trichosomoides crassicauda
  • Contact with eggs of the parasite through the contaminated urine of infected rats
  • Unsanitary living conditions




Bladder threadworm is usually diagnosed by conducting urinary tests and examining the urine for the presence of eggs of the parasite.