The kidney worm is blood-red in color and is one of the largest of the parasitic roundworms. As their name implies, kidney worms usually occur in the kidneys and more frequently in the right organ than in the left. The presence of the worms in the kidney results in the destruction of the functional tissue of the organ, leaving only a greatly distended and thickened kidney capsule containing worms, fluid and a speculated, bony plate. The only treatment for this parasite is surgical removal.
Genus : Dioctophyme
“The Giant Kidney Worm of Carnivores.”
There has been some confusion about the history of discovery of D. renale but formal research investigating the life cycle of this parasite was started as early as 1782. The general life cycle of this parasite was known, but further life-cycle information was discovered in the mid to latter part of the 20th century.
Ø Kidney parenchyma destroyed, capsule distended, calcification occurs
Ø Adhesions, peritonitis from worms in body cavity
Ø Unaffected kidney has compensatory hypertrophy
Ø Frequently no clinical signs because of compensation, but possibly :
Ø Severe abdominal and lumbar pain, paresis of the hindquarters
Ø Sudden weight loss (up to 1/2), anorexia, vomiting
Ø Hematuria, polydipsia, uremia
Ø Severe pain and irritation resulting from adults attempting to migrate through the ureters.
The eggs pass out in the urine of the final host and develop in water to the infective stage (1 to 7 months). When the infective egg is swallowed by an oligochaete annelid it hatches and develops over a period of about 100 days to the third stage larva. If the worm is eaten by a frog or fish the third stage-larva will encyst in the predator (paratenic host). When the worm, frog or fish ( paratenic host) is eaten by the definitive host the larva penetrates the intestinal wall, develop for a while in the body cavity and then enter the right kidney. The parasite matures to the adult stage in the kidney destroying the parenchyma of this organ. Eggs are laid in the kidney and pass out with the urine.
Generally a parasite of wild mustelids, especially mink; also reported in canids, bears, raccoons, otters, seals, domestic animals such as horses, cattle, and swine, and humans (definitive).
Oligochaete annelids (intermediate)
Fish and frogs (paratenic)
measure on average:
male: up to 35 cm x 3-6 mm wide
female up to 103 cm x 5-12 mm wide
Both sexes are blood red in color with a round body and blunt slightly tapered ends.
Dioctophyme adults. Note the ruler (150 mm). The female worm is at the top of the image.
Photo courtesy of http://www.biosci.ohio-state.edu/~parasite/dioctophyme.html
Eggs - barrel-shaped, shell pitted except at the poles. Roughly 71-84 x 46-52 microns
Image courtesy of :
Incubation period: Eggs embryonate in 2 weeks to 3 months; Juvenile larvae mature over period of about 50 days in liver parenchyma. They migrate directly to kidney further mature and may remain alive for up to 5 years.
Ø Eggs in urine (if adults are present in the kidney)
Ø Adults recovered during laparotomy or hysterectomy (usually when in the abdominal cavity) or at necropsy
Surgical removal of the parasite.
Cases of D. renale have been reported in virtually every part of the world with a temperate climate. In North America, cases are primarily found in Michigan, Minnesota and Wisconsin. D. renale is a very rare parasite of humans, having been reported only 3 times.
Human infections have been rare, with only three on record. In these cases worms were found in the kidneys and larvae were found in subcutaneous nodules. These cases are of unknown etiology, but are thought to have been caused by the consumption of raw fish. Because the rarity of dioctophyme renale infection in humans, no public health measures have been taken.
1) Barros DM, Lorini ML, Persson VG, Dioctophymosis in the little grison (Galictis cuja). Journal of Wildlife Discovery 1990 Oct;26(4):538-9
2) Crichton VJ, Urban RE, Dioctophyme renale (Goeze, 1782) (Nematoda: Dioctophymata) in Manitoba mink Canandian Journal of Zoology 1970 May;48(3):591-2
3) Fernando, SS, The giant kidney worm (Dioctophyma renale) infection in man in Australia. American Journal of Surgical Pathology. 1983 Apr;7(3):281-284
4) Mace TF, Anderson RC, Development of the giant kidney worm, Dioctophyma renale (Nematoda: Dioctophymatoidea). Canadian Journal of Zoology. 1975 Nov;53(11):1552-68.
5) Measures LN, Anderson RC, Centrarchid fish as paratenic hosts of the giant kidney worm, Dioctophyma renale in Ontario, Canada. Journal of Wildlife Discovery . 1985 Jan;21(1):11-9.
6) Sun T, Turnbull A, Lieverman PH, Sternberg SS. Giant kidney worm (Dioctophyma renale) infection mimicking retroperitoneal neoplasm. American Journal of Surgical Pathology. 1986 Jul;10(7):508-12.