Dioctophyme renale, the giant kidney worm.
Carnivores, including canids, mustelids and felids, serve as the usual definitive hosts for Dioctophyme renale. However, other mammals, including herbivores and humans, can become infected. Unembryonated eggs are shed in the urine of the definitive host and L1 larvae develop inside the egg after about a month in water. After being eaten by the invertebrate intermediate host (usually annelids, including earthworms), the eggs hatch in the digestive tract and mature into L3 larvae after two molts (usually 2-3 months at 20-30°C). If the intermediate host is eaten by a paratenic host (including fish and amphibians), the L3 larvae encyst and do not develop any further . The definitive host then becomes infected after eating a paratenic host housing encysted L3 larvae . Definitive hosts may also become infected after directly consuming infected invertebrate intermediate hosts. After being ingested by the definitive host, the infective larvae migrate through the gastric wall to the liver, and eventually to the kidney. Worms become adults roughly six months after infecting the definitive host. Humans may also become infected after eating undercooked paratenic hosts . Although humans may serve as definitive hosts, often the larvae wind up in subcutaneous nodules and do not develop any further.
Most of the earlier reports of dioctophymiasis in humans involved the finding of eggs or adult worms in urine. There is one report of a worm rupturing through the body wall (fistula) from an abscessed kidney. There are also a few more recent reports of L3 larvae being found in migratory, subcutaneous nodules.
larvae of Dioctotphyme renale in human tissue.
Identification of eggs or adult worms in urine. Adults may also be found during laparotomy or hysterectomy (or necropsy) when in the abdominal cavity. L3 larvae in subcutaneous nodules may be observed in stained tissue sections.
DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/.