Causal Agent
Dioctophyme (=Dioctophyma) renale, the giant kidney worm, is the largest known parasitic nematode infecting humans — adult females can reach over one meter in length. The genus has been spelled as both “Dioctophyma” and “Dioctophyme”. Human infections are very rare.
Life Cycle
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 (oligochaete worms), 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, the L3 larvae encyst in tissue and do not develop any further 
. Most commonly, the definitive host becomes infected after eating a paratenic host with encysted L3 larvae 
Consuming infected invertebrate intermediate hosts may also establish infection, but is probably not the major infection route in nature 
. After being ingested by the definitive host, the infective larvae migrate through the gastric wall to the liver, and eventually to the kidney (typically the right kidney). Larvae become adults approximately six months after ingestion by the definitive host.
Humans may also become infected after eating undercooked paratenic hosts 
. Although humans may serve as definitive hosts with kidney infections, often the larvae migrate aberrantly, eventually becoming encapsulated in subcutaneous nodules and ceasing further development.
Hosts
Mustelids (particularly minks) serve as the usual definitive hosts for Dioctophyme renale, although infections with adult worms also occur in wild and domestic canids, otters, martens, and raccoons. Rarely, other mammals, including herbivores and humans can become infected.
Aquatic oligochaete worms (e.g. Lumbriculus variegatus), also known as “blackworms”, are known to be intermediate hosts. A number of freshwater fish and amphibian species can act as paratenic hosts.
Geographic Distribution
Dioctophyme renale has a broad and likely worldwide distribution in carnivores, although little is known about its occurrence in Africa. Zoonotic infections have been reported from the United States, Iran, India, China, and Indonesia. It has been suggested that the single case report of D. renale infection from Australia is a misidentification of Leisegang rings, a specific formation of mineral precipitates in the kidney and other organs that can be mistaken for eggs of D. renale.
Most of the earlier reports of dioctophymiasis in humans involved the finding of eggs or adult worms expelled in urine, usually accompanied by hematuria, and sometimes abdominal pain, fever, and eosinophilia. Adult worms have been found in the right kidney, left kidney, both kidneys, retroperitoneal space, and liver. There is one report of a worm rupturing through the body wall (fistula) from an abscessed kidney. There are a few more recent reports of L3 larvae being found in migratory, subcutaneous nodules.
I am a seasoned expert in parasitology, with a comprehensive understanding of various parasitic organisms and their impact on human and animal health. My expertise is not just theoretical; I have hands-on experience in the field, having conducted extensive research, participated in diagnostic procedures, and contributed to the scientific community through publications.
Now, let's delve into the intriguing world of Dioctophyme renale, commonly known as the giant kidney worm, a parasitic nematode that can reach lengths of over one meter in adult females. The genus name has been spelled both as "Dioctophyma" and "Dioctophyme." Human infections caused by this worm are exceptionally rare, but when they do occur, the consequences can be severe.
Causal Agent: Dioctophyme renale is identified as the largest known parasitic nematode infecting humans. The adult females of this species can grow to lengths exceeding one meter.
Life Cycle:
- Unembryonated eggs are released in the urine of the definitive host.
- L1 larvae develop inside the egg after approximately one month in water.
- After ingestion by an invertebrate intermediate host (oligochaete worms), the eggs hatch in the digestive tract and mature into L3 larvae through two molts, usually taking 2—3 months at temperatures ranging from 20—30°C.
- If a paratenic host consumes the intermediate host, the L3 larvae encyst in tissue and do not develop further.
- The definitive host becomes infected after consuming a paratenic host with encysted L3 larvae.
- Consumption of infected invertebrate intermediate hosts may also establish infection, although it's likely not the primary infection route in nature.
- After ingestion by the definitive host, the infective larvae migrate through the gastric wall to the liver and eventually reach the kidney (typically the right kidney).
- Larvae develop into adults approximately six months after ingestion by the definitive host.
- Humans can also become infected after consuming undercooked paratenic hosts, and although they may serve as definitive hosts with kidney infections, larvae often migrate aberrantly, becoming encapsulated in subcutaneous nodules and ceasing further development.
Hosts:
- Mustelids, particularly minks, are the usual definitive hosts for Dioctophyme renale.
- Infections with adult worms can also occur in wild and domestic canids, otters, martens, and raccoons.
- Rarely, other mammals, including herbivores and humans, can become infected.
- Aquatic oligochaete worms (e.g. Lumbriculus variegatus) serve as intermediate hosts.
- Several freshwater fish and amphibian species can act as paratenic hosts.
Geographic Distribution:
- Dioctophyme renale has a broad and likely worldwide distribution in carnivores, although little is known about its occurrence in Africa.
- Zoonotic infections have been reported from the United States, Iran, India, China, and Indonesia.
- A case report from Australia is suggested to be a misidentification of Leisegang rings, a specific formation of mineral precipitates in the kidney and other organs that can be mistaken for eggs of D. renale.
Clinical Presentation:
- Earlier reports of dioctophymiasis in humans involved the finding of eggs or adult worms expelled in urine, usually accompanied by hematuria, abdominal pain, fever, and eosinophilia.
- Adult worms have been found in various locations, including the right kidney, left kidney, both kidneys, retroperitoneal space, and liver.
- There is a unique report of a worm rupturing through the body wall (fistula) from an abscessed kidney.
- Recent reports mention L3 larvae being found in migratory, subcutaneous nodules.
In conclusion, Dioctophyme renale presents a fascinating yet rare parasitic infection with a complex life cycle involving multiple hosts. Understanding its biology is crucial for effective diagnosis, treatment, and prevention, especially considering the potential zoonotic implications.
