Diphyllobothriasis | |
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Specialty | Infectious diseases, helminthologist |
Diphyllobothriasis is the infection caused by tapeworms of the genus Diphyllobothrium (commonly D. latum and D. nihonkaiense).
Diphyllobothriasis mostly occurs in regions where raw fish is regularly consumed; those who consume raw fish are at risk of infection. The infection is often asymptomatic and usually presents only with mild symptoms, which may include gastrointestinal complaints, weight loss, and fatigue. Rarely, vitamin B12 deficiency (possibly leading to anaemia) and gastrointestinal obstructions may occur. Infection may be long-lasting in absence of treatment. Diphyllobothriasis is generally diagnosed by looking for eggs or tapeworm segments in passed stool. Treatment with antiparasitic medications is straightforward, effective, and safe.
Most infections (~80% [6] ) are asymptomatic. [6] [7] [8] Infections may be long-lasting, [7] persisting for many years [6] or decades (up to 25 years) [7] if untreated.
Symptoms (when present) are generally mild. [9] [8] Manifestations may include abdominal pain and discomfort, diarrhea, vomiting, constipation, weight loss, and fatigue. [9]
Additional symptoms have been reported/described, including dyspepsia, abdominal distension (commonly as presenting complaint), headache, myalgia, and dizziness. [8]
While the infection is generally mild, complications may occur. Complications are predicated on parasite burden, and are generally related to vitamin B12 deficiency and related health conditions. [8]
Vitamin B12 deficiency with subsequent megaloblastic anaemia (which is indistinguishable from pernicious anaemia) may occur in some instances of the disease. [10] Anaemia may in turn result in subacute combined degeneration of the spinal cord and cognitive decline. [8]
D. latum competes with the host for vitamin B12 absorption, [11] absorbing some 80% of dietary intake and causing deficiency and megaloblastic anaemia in some 40% of cases. [12] Vitamin B12 uptake is enabled by the position of the parasite which usually lodges in the jejunum. [13] Vitamin B12 deficiency is – according to research – conversely seldom seen in D. pacificum infection. [11]
Rarely, massive infections may result in intestinal obstruction. Migration of proglottids can cause cholecystitis or cholangitis. [7]
Diphyllobothriasis is caused by infection by several species of the Diphyllobothrium genus. [7]
Humans are one of the definitive hosts of Diphyllobothrium tapeworms, along with other carnivores, fish-eating mammals (including canids, felids, and bears), marine mammals (dolphins, porpoises, and whales); a few birds (e.g. gulls) may also serve as definitive hosts. [7]
Definitive hosts release eggs in faeces; the eggs then mature in ~18–20 days if under favourable conditions. Crustaceans serve as the first intermediate hosts, and Diphyllobothrium larvae develop. The larvae are released when crustaceans are consumed by predators, which serve as second intermediate hosts (these are mostly small fish). Larvae move into deeper tissues in the second intermediate host. Second intermediate hosts do not serve as an important source of infection of humans as these are not regularly consumed raw. Consumption of infected second intermediate hosts by larger predatory fish, which serve as paratenic hosts; the parasites thereupon migrate into the musculature awaiting consumption by definitive hosts in which adult tapeworms will then finally develop in the small intestine to release up to a million immature eggs per day per parasite. Hosts begin to release eggs 5–6 weeks after infection. [7]
Tapeworms develop in the small intestine. Adults attach to the intestinal mucosa. Adult tapeworms may grow to over 10 m in length and may constitute of over 3,000 proglottids [7] which contain sets of male and female reproductive organs, allowing for high fecundity. [8] Eggs appear in the faeces 5–6 weeks after infection. [7]
D. latum tapeworms are the longest and typically reach a length of 4–15 m, but may grow up to 25 m in length within the human intestine. Growth rate may exceed 22 cm/day. D. latum tapeworms feature an anterior end (scolex) equipped with attachment grooves on the dorsal and ventral surfaces. [8]
Diphyllobothriasis is postulated to cause changes in neuromodulator concentrations in host tissue and serum. D. latum infection has been shown to cause local changes in the host, leading to altered GI function (including motility) via neuroendocrine modulation. [8]
Diphyllobothriasis causes mast cell and eosinophil degranulation, leading to pro-inflammatory cytokine release. [8]
Infection may be suspected based upon an individual's occupation, hobbies, eating habits, and travel history. [8] During diagnostic procedures, standard safety precautions apply. Eggs are not directly infectious to humans (in contrast to some other tapeworm species). [7]
Diagnosis is usually made by identifying proglottid segments, or characteristic eggs in the faeces. [14] Eggs are usually numerous and can be demonstrated without concentration techniques. Morphologic comparison with other intestinal parasites may be employed as a further diagnostic approach.[ citation needed ]
These simple diagnostic techniques are able to identify the nature of the infection to the genus level, which is usually sufficient in a clinical setting. [6] Though it is difficult to identify the eggs or proglottids to the species level, the distinction is of little clinical importance because – like most adult tapeworms in the intestine – all members of the genus respond to the same treatments.[ citation needed ] Treatment may distort morphological features of expelled pathogen tissues and complicate subsequent morphological diagnosis attempts. [7]
When the exact species needs be determined (e.g. in epidemiological studies), restriction fragment length polymorphisms can be effectively used. Polymerase chain reaction (PCR) can be performed on samples of purified eggs, or on native faecal samples following sonication of the eggs to release their contents. [6] Molecular identification is currently generally only used in research. [7]
A potential diagnostic tool and treatment is the contrast medium gastrografin which, when introduced into the duodenum, allows both visualization of the parasite, and has also been shown to cause detachment and passing of the whole parasite. [15]
Ingestion of raw freshwater fish should be avoided. Adequate cooking or freezing of freshwater fish will destroy the encysted fish tapeworm larvae. Fish that is thoroughly cooked, brined, or frozen at −10 °C for 24–48 hours can also be consumed without risk of D. latum infection. Public health information campaigns may be employed to educate the public about the risks of consuming improperly prepared fish.[ citation needed ]
Because human feces are an important mechanism for spreading eggs, proper disposal of sewage can reduce fish (and therefore human) infections.[ citation needed ] Prevention of water contamination may be achieved both by raising public awareness of the dangers of defecating in recreational bodies of water and by implementation of basic sanitation measures and screening and successful treatment of people infected with the parasite. [6]
Upon diagnosis, treatment is simple and effective. [16] [17] [18]
Praziquantel
The standard treatment for diphyllobothriasis (as well as many other tapeworm infections) is a single dose of praziquantel, 5–10 mg/kg orally once for both adults and children. [16] [17] [18] Praziquantel is not FDA-approved for this indication. [16] Praziquantel has few side effects, many of which are similar to the symptoms of diphyllobothriasis. [6]
Niclosamide
An alternative treatment is niclosamide, 2 g orally once for adults or 50 mg/kg (max 2 g) for children. [16] [17] [18] Niclosamide is not available for human or even animal use in the United States. [16] Side effects of niclosamide are very rare due to the fact that the medication is not absorbed in the gastrointestinal tract. [6]
Other
Reportedly, albendazole can also be effective. [19] [20] Gastrografin may be potentially used both as a diagnostic and therapeutic; when introduced into the duodenum it allows for the visualization of the parasite, and has also been shown to cause detachment and passing of the whole worm. [21] [22] During the 1940s, the preferred treatment was 6 to 8 grams of oleoresin of aspidium, which was introduced into the duodenum via a Rehfuss tube. [23]
People at high risk for infection have traditionally been those who regularly consume raw fish. [6] While people of any gender or age may fall sick, the majority of identified cases occurred in middle-aged men. [8]
Diphyllobothriasis occurs in areas where lakes and rivers coexist with human consumption of raw or undercooked freshwater fish. [24] Such areas are found in Europe, newly independent states of the former Soviet Union, North America, Asia, Uganda, Peru (because of ceviche), and Chile. [24] Many regional cuisines include raw or undercooked food, including sushi and sashimi in Japanese cuisine, carpaccio di persico in Italian, tartare maison in French-speaking populations, ceviche in Latin American cuisine and marinated herring in Scandinavia. With emigration and globalization, the practice of eating raw fish in these and other dishes has brought diphyllobothriasis to new parts of the world and created new endemic foci of disease. [6]
Infections in Europe and North America were traditionally associated with Jewish women due to the practice of tasting bits of uncooked fish during preparation of the gefilte fish dish, [25] and also occurred in Scandinavian women for the same reason. Diphyllobothriasis was thus also referred to as the "Jewish housewife's disease" or the "Scandinavian housewife's disease". [26]
Diphyllobothriasis nihonkaiense was once endemic to coastal provinces of central and northern Japan, where salmon fisheries thrived. [24] In recent decades, regions with endemic diphyllobothriasis nihonkaiense have disappeared from Japan, though cases continue to be reported among urbanites who consume sushi or sashimi. [24] In Kyoto, it is estimated that the average annual incidence in the past 20 years was 0.32/100,000, and that in 2008 was 1.0 case per 100,000 population, suggesting that D. nihonkaiense infection is equally as prevalent in Japan as D. latum is in some European countries. [24]
The disease is rare in the United States.[ citation needed ]
The fish tapeworm has a long documented history of infecting people who regularly consume fish and especially those whose customs include the consumption of raw or undercooked fish. In the 1970s, most of the known cases of diphyllobothriasis came from Europe (5 million cases), and Asia (4 million cases) with fewer cases coming from North America and South America, and no reliable data on cases from Africa or Australia. [6] Despite the relatively small number of cases seen today in South America, some of the earliest archeological evidence of diphyllobothriasis comes from sites in South America. Evidence of Diphyllobothrium spp. has been found in 4,000- to 10,000-year-old human remains on the western coast of South America. [27] There is no clear point in time when Diphyllobothrium latum and related species were "discovered" in humans, but it is clear that diphyllobothriasis has been endemic in human populations for a very long time. Due to the changing dietary habits in many parts of the world, autochthonous, or locally acquired, cases of diphyllobothriasis have recently been documented in previously non-endemic areas, such as Brazil. [28] In this way, diphyllobothriasis represents an emerging infectious disease in certain parts of the world where cultural practices involving eating raw or undercooked fish are being introduced.[ citation needed ]
Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is used to treat schistosomiasis, clonorchiasis, opisthorchiasis, tapeworm infections, cysticercosis, echinococcosis, paragonimiasis, fasciolopsiasis, and fasciolosis. It should not be used for worm infections of the eye. It is taken by mouth.
Clonorchiasis is an infectious disease caused by the Chinese liver fluke and two related species. Clonorchiasis is a known risk factor for the development of cholangiocarcinoma, a neoplasm of the biliary system.
Diphyllobothrium is a genus of tapeworms which can cause diphyllobothriasis in humans through consumption of raw or undercooked fish. The principal species causing diphyllobothriasis is D. latum, known as the broad or fish tapeworm, or broad fish tapeworm. D. latum is a pseudophyllid cestode that infects fish and mammals. D. latum is native to Scandinavia, western Russia, and the Baltics, though it is now also present in North America, especially the Pacific Northwest. In Far East Russia, D. klebanovskii, having Pacific salmon as its second intermediate host, was identified.
Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or H. diminuta. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a neglected tropical disease.
Megaloblastic anemia is a type of macrocytic anemia. An anemia is a red blood cell defect that can lead to an undersupply of oxygen. Megaloblastic anemia results from inhibition of DNA synthesis during red blood cell production. When DNA synthesis is impaired, the cell cycle cannot progress from the G2 growth stage to the mitosis (M) stage. This leads to continuing cell growth without division, which presents as macrocytosis. Megaloblastic anemia has a rather slow onset, especially when compared to that of other anemias. The defect in red cell DNA synthesis is most often due to hypovitaminosis, specifically vitamin B12 deficiency or folate deficiency. Loss of micronutrients may also be a cause.
Anisakis is a genus of parasitic nematodes that have life cycles involving fish and marine mammals. They are infective to humans and cause anisakiasis. People who produce immunoglobulin E in response to this parasite may subsequently have an allergic reaction, including anaphylaxis, after eating fish infected with Anisakis species.
Taenia solium, the pork tapeworm, belongs to the cyclophyllid cestode family Taeniidae. It is found throughout the world and is most common in countries where pork is eaten. It is a tapeworm that uses humans as its definitive host and pigs as the intermediate or secondary hosts. It is transmitted to pigs through human feces that contain the parasite eggs and contaminate their fodder. Pigs ingest the eggs, which develop into larvae, then into oncospheres, and ultimately into infective tapeworm cysts, called cysticercus. Humans acquire the cysts through consumption of uncooked or under-cooked pork and the cysts grow into adult worms in the small intestine.
Dwarf tapeworm is a cosmopolitan species though most common in temperate zones, and is one of the most common cestodes infecting humans, especially children.
Hymenolepis diminuta, also known as rat tapeworm, is a species of Hymenolepis tapeworm that causes hymenolepiasis. It has slightly bigger eggs and proglottids than H. nana and infects mammals using insects as intermediate hosts. The adult structure is 20 to 60 cm long and the mature proglottid is similar to that of H. nana, except it is larger.
Taenia pisiformis, commonly called the rabbit tapeworm, is an endoparasitic tapeworm which causes infection in lagomorphs, rodents, and carnivores. Adult T. pisiformis typically occur within the small intestines of the definitive hosts, the carnivores. Lagomorphs, the intermediate hosts, are infected by fecal contamination of grasses and other food sources by the definitive hosts. The larval stage is often referred to as Cysticercus pisiformis and is found on the livers and peritoneal cavities of the intermediate hosts. T. pisiformis can be found worldwide.
Taeniasis is an infection within the intestines by adult tapeworms belonging to the genus Taenia. There are generally no or only mild symptoms. Symptoms may occasionally include weight loss or abdominal pain. Segments of tapeworm may be seen in the stool. Complications of pork tapeworm may include cysticercosis.
Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda. Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cestodaria. All tapeworms are endoparasites of vertebrates, living in the digestive tract or related ducts. Examples are the pork tapeworm with a human definitive host, and pigs as the secondary host, and Moniezia expansa, the definitive hosts of which are ruminants.
Spirometra erinaceieuropaei is a parasitic tapeworm that infects domestic animals and humans. The medical term for this infection in humans and other animals is sparganosis. Morphologically, these worms are similar to other worms in the genus Spirometra. They have a long body consisting of three sections: the scolex, the neck, and the strobilia. They have a complex life cycle that consists of three hosts, and can live in varying environments and bodily tissues. Humans can contract this parasite in three main ways. Historically, humans are considered a paratenic host; however, the first case of an adult S. erinaceieuropaei infection in humans was reported in 2017. Spirometra tapeworms exist worldwide and infection is common in animals, but S. erinaceieuropaei infections are rare in humans. Treatment for infection typically includes surgical removal and anti-worm medication.
Hymenolepis is a genus of cyclophyllid tapeworms that cause hymenolepiasis. They parasitise mammals, including humans. Some notable species are:
Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of many similar units known as proglottids—essentially packages of eggs which are regularly shed into the environment to infect other organisms. Species of the other subclass, Cestodaria, are mainly fish infecting parasites.
Diphyllobothrium mansonoides is a species of tapeworm (cestodes) that is endemic to North America. Infection with D. mansonoides in humans can result in sparganosis. Justus F. Mueller first reported this organism in 1935. D. mansonoides is similar to D. latum and Spirometra erinacei. When the organism was discovered, scientist did not know if D. mansonoides and S. erinacei were separate species. PCR analysis of the two worms has shown the two to be separate but closely related organisms.
Raillietina is a genus of tapeworms that includes helminth parasites of vertebrates, mostly of birds. The genus was named in 1920 in honour of a French veterinarian and helminthologist, Louis-Joseph Alcide Railliet. Of the 37 species recorded under the genus, Raillietina demerariensis, R. asiatica, and R. formsana are the only species reported from humans, while the rest are found in birds. R. echinobothrida, R. tetragona, and R. cesticillus are the most important species in terms of prevalence and pathogenicity among wild and domestic birds.
Diphyllobothrium dendriticum is a large pseudophyllid cestode of the family Diphyllobothriidae.
Gastropod-borne parasitic diseases (GPDs) are a group of infectious diseases that require a gastropod species to serve as an intermediate host for a parasitic organism that can infect humans upon ingesting the parasite or coming into contact with contaminated water sources. These diseases can cause a range of symptoms, from mild discomfort to severe, life-threatening conditions, with them being prevalent in many parts of the world, particularly in developing regions. Preventive measures such as proper sanitation and hygiene practices, avoiding contact with infected gastropods and cooking or boiling food properly can help to reduce the risk of these diseases.