Dioctophyme renale
Encyclopedia
Dioctophyme renale is commonly referred to as “giant kidney worm” because it is the largest helminth to parasitize humans and has the propensity to affect the kidneys. D. renale is distributed worldwide, but is less common in Africa and Oceania. It affects fish eating mammals, particularly mink and dogs. Human infestation is rare, but results in destruction of the kidneys. Upon diagnosis through tissue sampling, the only treatment is surgical excision.
in 1989.
In 2003, D. renale eggs were discovered in six human coprolites in the neolithic site Arbon-Bleiche 3, Switzerland. This location is located near a lake, which likely provided early humans with access to freshwater fish and frogs. The samples were dated from 3,384-3,370 BC, and is evidence that the prevalence of this infection was higher in early human history (before full understanding of proper cooking techniques).
(blood in urine), nephritis
, loin pain, renal enlargement, and/or renal colic
(intermittent pain in the kidney area), which may result from the rare migration of worms through ureters.
Adult worms typically only infect one kidney. The kidney is destroyed because of fibrosis
, the development of excess fibrous connective tissue. Renal function is typically limited because the non-infected kidney is usually capable of assuming the increased work. However, parenchymal inflammation (i.e., inflammation of the functional parts of an organ) can lead to death in extreme circumstances.
host may then ingest the oligochaete. The oligochaete or paratenic
host is then eaten by a definitive host, wherein juveniles penetrate intestinal lining and migrate to the liver. After maturing for approximately 50 days, the juveniles then migrate to the kidneys (typically the right kidney). Upon maturation, D. renale can survive for five years.
Intermediate hosts are oligochaete annaelids
Definitive hosts are carnivorous mammals, notably mink
, but also includes wolves, coyotes, foxes, dogs, raccoons, and weasels.
Transmission to humans typically occurs upon ingestion of raw or undercooked freshwater fish or frog.
There are multiple reservoirs for D. renale. Confirmed cases of infection have occurred in minks, dogs, swine, bears, oxen, and humans.
Eggs are 60-80 micrometres x 39-47 micrometres, contain an embryo, and have characteristic sculpturing of the shell. They have an oval-shape and brownish-yellow hue. Eggs have a thick shell, and the surface appears to be pitted except at the poles.
will likely show hematuria blood tests may reveal eosinophilia.
is generally considered extreme for human cases.
A physician reportedly used Ivermectin to treat a patient, who was effectively cured. The use of anti-helminth drugs has not yet been evaluated as the proper course of action to treat this infection.
Non-human infections are more common worldwide, especially in areas of temperate climate. Prevalence in mink populations may be high, such as portions of Ontario or Minnesota. Similarly, some minnow populations may be as high as 50%.
History of discovery
Dioctophyme renale was discovered in 1583. Almost two centuries later, in 1782, Johann Goeze first described D. renale upon discovering the worms in a dog kidney. The family Dioctophymidae has only one genus (Dioctophyme), and the name of the genus was in contention (with the possibility of being Dioctophyma) for two hundred years. The issue was finally resolved by the International Commission on Zoological NomenclatureInternational Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...
in 1989.
In 2003, D. renale eggs were discovered in six human coprolites in the neolithic site Arbon-Bleiche 3, Switzerland. This location is located near a lake, which likely provided early humans with access to freshwater fish and frogs. The samples were dated from 3,384-3,370 BC, and is evidence that the prevalence of this infection was higher in early human history (before full understanding of proper cooking techniques).
Clinical presentation in humans
Individuals with Dicotophyme renalis infection typically present with unspecific symptoms including hematuriaHematuria
In medicine, hematuria, or haematuria, is the presence of red blood cells in the urine. It may be idiopathic and/or benign, or it can be a sign that there is a kidney stone or a tumor in the urinary tract , ranging from trivial to lethal...
(blood in urine), nephritis
Nephritis
Nephritis is inflammation of the nephrons in the kidneys. The word "nephritis" was imported from Latin, which took it from Greek: νεφρίτιδα. The word comes from the Greek νεφρός - nephro- meaning "of the kidney" and -itis meaning "inflammation"....
, loin pain, renal enlargement, and/or renal colic
Renal colic
Renal colic is a type of abdominal pain commonly caused by kidney stones.-Presentation:The pain typically begins in the abdomen and often radiates to the hypochondrium or the groin. The pain is often colicky due to ureteric peristalsis, but may be constant...
(intermittent pain in the kidney area), which may result from the rare migration of worms through ureters.
Adult worms typically only infect one kidney. The kidney is destroyed because of fibrosis
Fibrosis
Fibrosis is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process. This is as opposed to formation of fibrous tissue as a normal constituent of an organ or tissue...
, the development of excess fibrous connective tissue. Renal function is typically limited because the non-infected kidney is usually capable of assuming the increased work. However, parenchymal inflammation (i.e., inflammation of the functional parts of an organ) can lead to death in extreme circumstances.
Transmission and life cycle
Adult Dioctophyme renale inhabit the kidney (typically the right kidney). Females produce eggs which are passed in urine. In aquatic environments, eggs embryonate after 15–100 days. These eggs are ingested by an aquatic oligochaete, hatch, penetrate blood vessels, and develop into a stage three larvae. A paratenicParatenic
In parasitology, the term paratenic describes a host which is not needed for the development of the parasite, but nonetheless serves to maintain the life cycle of the parasite. Alaria americana may serve as an example: the so-called mesocercarial stages of this parasite reside in tadpoles, which...
host may then ingest the oligochaete. The oligochaete or paratenic
Paratenic
In parasitology, the term paratenic describes a host which is not needed for the development of the parasite, but nonetheless serves to maintain the life cycle of the parasite. Alaria americana may serve as an example: the so-called mesocercarial stages of this parasite reside in tadpoles, which...
host is then eaten by a definitive host, wherein juveniles penetrate intestinal lining and migrate to the liver. After maturing for approximately 50 days, the juveniles then migrate to the kidneys (typically the right kidney). Upon maturation, D. renale can survive for five years.
Intermediate hosts are oligochaete annaelids
Definitive hosts are carnivorous mammals, notably mink
Mink
There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and...
, but also includes wolves, coyotes, foxes, dogs, raccoons, and weasels.
Transmission to humans typically occurs upon ingestion of raw or undercooked freshwater fish or frog.
There are multiple reservoirs for D. renale. Confirmed cases of infection have occurred in minks, dogs, swine, bears, oxen, and humans.
Morphology
D. renale is the largest helminth to parasitize humans. Adult male worms are 20–40 cm long and 5–6 mm wide; females can grow to 103 cm in length with a width of 10–12 mm. Both sexes appear bright red in color and taper at both the anterior and posterior ends. Male D. renale worms have a bursa, which is used to attach to facilitate mating.Eggs are 60-80 micrometres x 39-47 micrometres, contain an embryo, and have characteristic sculpturing of the shell. They have an oval-shape and brownish-yellow hue. Eggs have a thick shell, and the surface appears to be pitted except at the poles.
Diagnosis
The only means of obtaining a definitive diagnosis is through the identification of D. renale eggs in a patient’s urine. However, obtaining patient history (i.e., if the patient has consumed undercooked or raw freshwater fish) is an important first step that can be coupled with radiological exams to search for enlarged or calcified kidneys. UrinalysisUrinalysis
A urinalysis , also known as Routine and Microscopy , is an array of tests performed on urine, and one of the most common methods of medical diagnosis...
will likely show hematuria blood tests may reveal eosinophilia.
Management and therapy
Likely because of the rarity of human cases, there is no standard treatment for D. renale infection in humans. The only means of known means is surgical excision of either adult worms or the infected kidney. NephrectomyNephrectomy
Nephrectomy is the surgical removal of a kidney.-History:The first successful nephrectomy was performed by the German surgeon Gustav Simon on August 2, 1869 in Heidelberg. Simon practiced the operation beforehand in animal experiments...
is generally considered extreme for human cases.
A physician reportedly used Ivermectin to treat a patient, who was effectively cured. The use of anti-helminth drugs has not yet been evaluated as the proper course of action to treat this infection.
Epidemiology
Though D. renale is distributed worldwide, though markedly less frequent in Africa and Oceana, human infection is extremely rare. Regions around the Caspian Sea have the highest number of cases, with the most occurring in Iran. Infections are also most commonly found in areas where freshwater fish is a dietary mainstay.Non-human infections are more common worldwide, especially in areas of temperate climate. Prevalence in mink populations may be high, such as portions of Ontario or Minnesota. Similarly, some minnow populations may be as high as 50%.
Public Health and Prevention Strategies
No public health measures have been undertaken or vaccines developed because of the rarity of human infection. The majority of D. renale infections have resulted from undercooked or raw freshwater fish consumption. Thus, the simple practice of thoroughly cooking fish prior to consumption could be promoted and lead to eradication of D. renale infection in humans.External links
- Giant Kidney Worm - Youtube video showing the removal of five giant kidney worms from a dog.