Gastrodiscoides

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Gastrodiscoides
Gastrodiscoides hominis longitudinal section.png
Longitudinal section of an adult
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Trematoda
Order: Plagiorchiida
Family: Paramphistomidae
Genus: Gastrodiscoides
Leiper, 1913
Species:
G. hominis
Binomial name
Gastrodiscoides hominis
(Lewis and McConnell, 1876)
Synonyms

Gastrodiscus hominisFischoeder
Amphistomum hominisLewis and McConnell

Contents

Gastrodiscoides is genus of zoonotic trematode under the class Trematoda. It has only one species, Gastrodiscoides hominis. It is a parasite of a variety of vertebrates, including humans. The first definitive specimen was described from a human subject in 1876. [1] It is prevalent in Bangladesh, India, Burma, China, Kazakhstan, Philippines, Thailand, Vietnam, and the Volga Delta of Russia, [2] [3] with isolated cases from Africa, such as Nigeria. [4] It is especially notable in the Assam, Bengal, Bihar, Madhya Pradesh, Orissa and Uttar Pradesh regions of India. [5] [2]

It is also known as the colonic fluke, particularly when infecting other animals. Its natural habitat is the colon of pigs, and has also been found in rhesus monkeys, orang-utans, fish, field rats and Napu mouse-deer. In humans the habitat is on the wall of the caecum. [6] [7] Humans are considered an accidental host, as the parasite can survive without humans. It causes a helminthic disease called gastrodiscoidiasis. [6] [7]

History of discovery

G. humanis is unique among helminths because it was first discovered and described from a human infection. The worm was discovered and described by two British medical doctors, Timothy Richard Lewis and James McConnell, in 1876, from the caecum of an indigenous Assamese man in India. Their description of the internal structure was inaccurate and incomplete. They claimed that the parasite had one testis and one ovary. They placed it in the genus Amphistomum, because of its obvious location of posterior sucker; the species was named Amphistomum hominis, as it was found in human. [8] In 1902, F. Fischoeder recognised the affinity with other species and tentatively placed it in the genus Gastrodiscus (Leuckart, 1877). However, the generic name was largely recognised as a synonym; it was then known as Amphistomum (Gastrodiscus) hominis. With a fresh look, J. W. W. Stephens re-described the parasite in 1906, and clearly noted the overlooked relatively small ovary and interpretation of the posterior testis as an ovary in the original description. [8]

A new helminthologist at the London School of Tropical Medicine, Robert T. Leiper, re-examined the parasite in 1913. He noted the distinctive characters such as a tuberculated genital cone, the position of the genital orifice, a smooth ventral disc, and the testes in tandem position. These outstanding features prompted him to create an entirely new genus, Gastrodiscoides, for the specimen. [9] This taxonomic revision had criticism, as some of the descriptions were later found to be flawed, such as the position of testes; these criticisms prevented it from coming into general acceptance. It was later observed that the parasite was much more common to pigs and other mammals than in humans. The first report of infection of pigs was in Cochinchina, Vietnam, in 1911. In 1913, it was further confirmed that the rate of porcine infection was as high as 5%. Then a large number of living flukes was recovered from dead Napu mouse-deer at the Zoological Gardens of the Zoological Society of London. The mouse-deer was Prince of Wales's collection from Malay. The shortcomings of Leiper's descriptions did not prevent the generic name Gastrodiscoides becoming more and more advocated in the early 1920s. [8] The currently accepted nomenclature was fortified by the British parasitologist J. J. C. Buckley, at the London School of Hygiene and Tropical Medicine (where he was then a Milner Research Fellow), whose descriptions were based on high incidence of the parasitism among the native Assamese ethnic groups in Northeastern India. His first report in 1939, [1] followed by a body of evidences in support of Leiper's proposition, enabled him to vindicate the validity of a separate genus, Gastrodiscoides, hence the binomial name Gastrodiscoides hominis. [10] His report was the pioneer description of the life cycle of the fluke and the prevalence of gastrodiscoidiasis. [1] In his survey of three villages in Assam, there was found a surprisingly high incidence, with over 40% of the population was infected. J. J. C. Buckley's report is the most useful to the modern classification of G. hominis. [11]

Description

It is typically an amphistome with the ventral sucker close to the posterior end. The body is bilaterally symmetrical and is acoelomate. It is dorsoventrally flatted, with a unique pyramidal shape. The body is covered by a tegument bearing numerous tubercles. [12] The alimentary canal is incomplete, consisting of a pair of lateral pouches arising from the oral sucker and a pharyngeal tube, which bifurcates into two gut caeca. The bladder is in the middle behind the ventral sucker. The genus is hermaphrodite, as both male and female reproductive system are present. [6] [8]

It is a large fluke, vase-shaped, and bright-pink in colour. In average it measures 5-8 mm long and 3-5 mm wide. The disc-shaped body is divisible into anterior conical and posterior discoidal regions. The anterior region is a conical projection bearing a prominent oral sucker. The posterior portion is relatively broad, up to 8 mm wide, discoidal, and ventrally excavated. It is an amphistome worm such that the ventral sucker is close to the posterior end. [13] The body covering, called a tegument, is smooth in appearance, but contains a fine structure in a series of concentric folds bearing numerous tightly packed tubercles. Ventral surface contains a specialised region of the tegument. Ciliated and non-ciliated papillae are arranged around the oral sucker. [14] [15] The incomplete alimentary canal consists of a pair of lateral pouches arising from the oral sucker and a slightly tortuous pharyngeal tube, which bifurcates into two gut caeca. The large excretory bladder is in the middle, behind the ventral sucker. The species, being hermaphrodite, has both male and female reproductive systems, arranged in the posterior region. The testes lie in alongside the bifurcation of the caeca, and a common genital pore is on the cone just anterior to the bifurcation. The oval-shaped ovary lies just posterior to the testes in the middle, and the loosely coiled uterus opens to the genital pore. Vitelline glands are scattered around the caeca. [8]

Biology

The Life Cycle of Gastrodiscoides hominis Gastrodiscoides hominis.png
The Life Cycle of Gastrodiscoides hominis

Humans are now considered as the accidental host because humans are not the primary requirement for the life cycle; pigs are recognised as the principal definitive host. Infection causes a helminthic disease called gastrodiscoidiasis. [6] It is a digenetic trematode with a complex life cycle involving asexual reproduction in an intermediate host, presumably aquatic snails, and sexual reproduction in the vertebrate host. As a hermaphrodite, eggs are produced by self-fertilisation and are released along the faeces of the host. Eggs measure ~146 by 66 μm, are rhomboidal in shape, transparent, and green in colour. Each egg contains about 24 vitelline cells and a central unembryonated ovum. Eggs in a wet environment hatch into miracidia in 9-14 days.

In water, eggs hatch into miracidia, which then infect a mollusc, in which larval development and fission occurs. The miracidium grows into the sporocyst stage. It is generally conceived that the unfertilised eggs are ingested by the snail, but there has been no direct observation. In an experimental infection of the mollusc Helicorbis coenosus, miracidum develops into cercaria after 28-153 days of ingestion. [16] In the snail, mother and daughter rediae are found in the digestive gland, and are about 148-747/45-140 μm in size, sausage-shaped, and lack collar and locomotory organs.

Infective cercariae are produced and are released on water plants or directly infect other aquatic animals, such as fish. [17] The cercariae released from the snail form metacercarial cysts on water plants. The complete life cycle is not yet observed in nature, [18] and the tiny snail, H. coenosus, remains the most commonly accepted vector, as it is coincidentally found in abundance in the pigsties. In some circumstances, fishes and other aquatic animals are found to be infected. It is hypothesised that the free cercaria in water bodies accidentally find and penetrate these animals as second intermediate host, where they encyst as metacercaria. These are directly infective to mammals upon consumption, while they get attached to vegetation, where night soil is used.

Humans ingest the metacercaria either by the infected fish or contaminated vegetable. The parasite travels through the digestive tract into the duodenum, then continues down to reach the caecum, where it self-fertilizes and lay eggs, continuing the cycle. Heavy infection in humans is suspected to cause diarrhoea, fever, abdominal pain, colic, malnutrition, anaemia, and even death. [2] [4]

Pathogenicity and pathology

A portion of human intestine slit open revealing Gastrodiscoides hominis Gastrodiscoides hominis infestation.png
A portion of human intestine slit open revealing Gastrodiscoides hominis

Gastrodiscoidiasis is an infection that is usually asymptomatic and affects the small intestine in animals, such as pigs, to a very mild symptom, but when it occurs in humans it can cause serious health problems and even death. It is suspected to cause diarrhoea, fever, abdominal pain, colic, and an increased mucous production. In severe cases, where there are large amounts of eggs present, tissue reactions can occur in the heart or mesenteric lymphatics, and even death may occur if left neglected. Indeed, a number of mortality among native Assamese children is attributed to this infection. [2] In pigs, pathological symptoms include infiltration with eosinophils, lymphocytes, and plasma cells. The submucosa can show oedema and thickening, resulting in a subacute inflammation of the caecum and mucoid diarrhoea. [6]

Epidemiology

Human gastrodiscoidiasis is endemic in Assam, and to a lesser extent in the Philippines. The highest incidence so far recorded is among children in Kamrup district of Assam, where the prevalence was as high as 41%. [1] First described from a native Assamese patient, it was initially believed to have a distribution restricted to NE India and the southeast Asia. Later investigations revealed that it is widespread, and is further spread by infected persons to other parts of the world, such as Guyana. [2] The level of infection in laboratory animals can be very high among Asian mammals. [13] Regions of high incidence can be attributed to low standard of sanitation, such as rural farms and villages where night soils are used. Infection in both humans and animals is most common through the ingestion of vegetation found in contaminated water. It is also assumed that transmission from infected fish that is under-cooked or eaten raw, as common among southeast Asian. [19] There is a unique case report of a seven-year-old Nigerian who showed symptoms of malnutrition and anaemia and was eventually diagnosed with infections of G. hominis and Ascaris lumbricoides. The child quickly recovered after proper medication. [4]

Diagnosis and treatment

Diagnosis is made by examination of the fæces and the detection of eggs. Adult worms are easily identified from other helminths by their distinctive appearance. The eggs are readily distinguished from those of other trematodes by their rhomboid shape and distinct green colour. Patients do not often directly show any symptoms, and if one appears, it indicates that the infection is already at a very high level. There is no prescribed treatment, but the traditional practice of soap enema has been very effective in removing the worms. [3] It works to flush the flukes from the colon which removes the parasite entirely, as it does not reproduce within the host. Some drugs that have been proven effective are tetrachloroethylene, at a dosage of 0.1 mg/kg on an empty stomach, and a more preferred drug, praziquantel, which eliminates the parasite with 3 doses at 25 mg/kg in one day. [6] Mebendazole was found to be efficient in deworming the parasite from a Nigerian girl who was shedding thousands of parasite eggs in stools even with a single dose of 500 mg. [4] Prevention of this disease is not difficult when simple sanitary measures are taken. Night soil should never be used as a fertilizer because it could contain any number of parasites. Vegetables should be washed thoroughly, and meat properly cooked. [7]

Related Research Articles

<span class="mw-page-title-main">Trematoda</span> Class of parasitic flatworms

Trematoda is a class of flatworms known as flukes or trematodes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive host, where the flukes sexually reproduce, is a vertebrate. Infection by trematodes can cause disease in all five traditional vertebrate classes: mammals, birds, amphibians, reptiles, and fish.

<i>Schistosoma</i> Genus of flukes

Schistosoma is a genus of trematodes, commonly known as blood flukes. They are parasitic flatworms responsible for a highly significant group of infections in humans termed schistosomiasis, which is considered by the World Health Organization as the second-most socioeconomically devastating parasitic disease, with hundreds of millions infected worldwide.

<span class="mw-page-title-main">Digenea</span> Class of flukes

Digenea is a class of trematodes in the Platyhelminthes phylum, consisting of parasitic flatworms with a syncytial tegument and, usually, two suckers, one ventral and one oral. Adults commonly live within the digestive tract, but occur throughout the organ systems of all classes of vertebrates. Once thought to be related to the Monogenea, it is now recognised that they are closest to the Aspidogastrea and that the Monogenea are more closely allied with the Cestoda. Around 6,000 species have been described to date.

<i>Fasciola hepatica</i> Species of fluke

Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode of the class Trematoda, phylum Platyhelminthes. It infects the livers of various mammals, including humans, and is transmitted by sheep and cattle to humans all over the world. The disease caused by the fluke is called fasciolosis or fascioliasis, which is a type of helminthiasis and has been classified as a neglected tropical disease. Fasciolosis is currently classified as a plant/food-borne trematode infection, often acquired through eating the parasite's metacercariae encysted on plants. F. hepatica, which is distributed worldwide, has been known as an important parasite of sheep and cattle for decades and causes significant economic losses in these livestock species, up to £23 million in the UK alone. Because of its relatively large size and economic importance, it has been the subject of many scientific investigations and may be the best-known of any trematode species. F. hepatica's closest relative is Fasciola gigantica. These two flukes are sister species; they share many morphological features and can mate with each other.

<span class="mw-page-title-main">Aspidogastrea</span> Species of fluke

The Aspidogastrea is a small group of flukes comprising about 80 species. It is a subclass of the trematoda, and sister group to the Digenea. Species range in length from approximately one millimeter to several centimeters. They are parasites of freshwater and marine molluscs and vertebrates. Maturation may occur in the mollusc or vertebrate host. None of the species has any economic importance, but the group is of very great interest to biologists because it has several characters which appear to be archaic.

<i>Fasciola</i> Genus of flukes

Fasciola, commonly known as the liver fluke, is a genus of parasitic trematodes. There are three species within the genus Fasciola: Fasciola nyanzae,Fasciolahepatica and Fasciolagigantica. Fasciola hepatica and F. gigantica are known to form hybrids. Both F. hepatica and F. gigantica and their hybrids infect the liver tissue of a wide variety of mammals, including humans, in a condition known as fascioliasis. F. hepatica measures up to 30 mm by 15 mm, while F. gigantica measures up to 75 mm by 15 mm. Fasciola nyanzae is thought to exclusively infect the common hippopotamus, Hippopotamus amphibius.

<span class="mw-page-title-main">Schistosomatidae</span> Family of flukes

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<i>Paragonimus westermani</i> Species of fluke

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<i>Schistosoma haematobium</i> Species of fluke

Schistosoma haematobium is a species of digenetic trematode, belonging to a group (genus) of blood flukes (Schistosoma). It is found in Africa and the Middle East. It is the major agent of schistosomiasis, the most prevalent parasitic infection in humans. It is the only blood fluke that infects the urinary tract, causing urinary schistosomiasis, and is the leading cause of bladder cancer. The diseases are caused by the eggs.

<i>Echinostoma</i> Genus of flukes

Echinostoma is a genus of trematodes (flukes), which can infect both humans and other animals. These intestinal flukes have a three-host life cycle with snails or other aquatic organisms as intermediate hosts, and a variety of animals, including humans, as their definitive hosts.

<i>Paragonimus</i> Genus of flukes

Paragonimus is a genus of flukes (trematodes) and is the only genus in the monotypic family Paragonimidae. Some tens of species have been described, but they are difficult to distinguish, so it is not clear how many of the named species may be synonyms. The name Paragonimus is derived from the combination of two Greek words, “para” and “gonimos”. Several of the species are known as lung flukes. In humans some of the species occur as zoonoses; the term for the condition is paragonimiasis. The first intermediate hosts of Paragonimus include at least 54 species of freshwater snails from superfamilies Cerithioidea and Rissooidea.

<span class="mw-page-title-main">Liver fluke</span> Group of liver parasites

Liver fluke is a collective name of a polyphyletic group of parasitic trematodes under the phylum Platyhelminthes. They are principally parasites of the liver of various mammals, including humans. Capable of moving along the blood circulation, they can occur also in bile ducts, gallbladder, and liver parenchyma. In these organs, they produce pathological lesions leading to parasitic diseases. They have complex life cycles requiring two or three different hosts, with free-living larval stages in water.

<i>Heterophyes heterophyes</i> Species of fluke

Heterophyes heterophyes, or the intestinal fish fluke, was discovered by Theodor Maximaillian Bilharz in 1851. This parasite was found during an autopsy of an Egyptian mummy. H. heterophyes is found in the Middle East, West Europe and Africa. They use different species to complete their complex lifestyle. Humans and other mammals are the definitive host, first intermediate host are snails, and second intermediate are fish. Mammals that come in contact with the parasite are dogs, humans, and cats. Snails that are affected by this parasite are the Cerithideopsilla conica. Fish that come in contact with this parasite are Mugil cephalus, Tilapia milotica, Aphanius fasciatus, and Acanthgobius sp. Humans and mammals will come in contact with this parasite by the consumption of contaminated or raw fish. This parasite is one of the smallest endoparasite to infect humans. It can cause intestinal infection called heterophyiasis.

<i>Clinostomum marginatum</i> Species of fluke

Clinostomum marginatum is a species of parasitic fluke. It is commonly called the "yellow grub". It is found in many freshwater fish in North America, and no fish so far is immune to this parasite. It is also found in frogs. Clinostomum marginatum can also be found in the mouth of aquatic birds such as herons and egrets. They are commonly present in the esophagus of fish-eating birds and reptiles. Eggs of these trematodes are shed in the feces of aquatic birds and released into water. Aquatic birds become hosts of this parasite by ingesting infected freshwater fish. The metacercariae are found right beneath the skin or in the muscles of host fish.

Megalodiscus temperatus is a Digenean in the phylum Platyhelminthes. This parasite belongs to the Cladorchiidae family and is a common parasite located in the urinary bladder and rectum of frogs. The primary host is frogs and the intermediate hosts of Megalodiscus temeperatus are freshwater snails in the genus Helisoma.

<i>Philophthalmus gralli</i> Species of fluke

Philophthalmus gralli, commonly known as the Oriental avian eye fluke, parasitises the conjunctival sac of the eyes of many species of birds, including birds of the orders Galliformes and Anseriformes. In Brazil this parasite was reported in native Anseriformes species. It was first discovered by Mathis and Leger in 1910 in domestic chickens from Hanoi, Vietnam. Birds are definitive hosts and freshwater snail species are intermediate hosts. Human cases of philophthalmosis are rare, but have been previously reported in Europe, Asia, and America.

Paramphistomum cervi, the type species of Paramphistomum, is a parasitic flat worm belonging to the class Trematoda. It is a tiny fluke mostly parasitising livestock ruminants, as well as some wild mammals. Uniquely, unlike most parasites, the adult worms are relatively harmless, but it is the developing juveniles that cause serious disease called paramphistomiasis, especially in cattle and sheep. Its symptoms include profuse diarrhoea, anaemia, lethargy, and often result in death if untreated.

Amphistomiasis is a parasitic disease of livestock animals, more commonly of cattle and sheep, and humans caused by immature helminthic flatworms belonging to the order Echinostomida. The term amphistomiasis is used for broader connotation implying the disease inflicted by members of Echinostomida including the family Paramphistomidae/Gastrodiscidae ; whereas paramphistomiasis is restricted to that of the members of the family Paramphistomidae only. G. discoides and Watsonius watsoni are responsible for the disease in humans, while most paramphistomes are responsible in livestock animals, and some wild mammals. In livestock industry the disease causes heavy economic backlashes due to poor production of milk, meat and wool.

Paragonimus kellicotti, the North American lung fluke, is a species of parasitic trematode in the genus Paragonimus. This species of Paragonimus has an intricate lifecycle, and although its name may suggest that it is only a health concern in North America, it is also prominent in Southeast Asia and China.

Schistosoma hippopotami is a species of digenetic trematode that belongs to the genus of blood flukes (Schistosoma) that is found in sub-Saharan Africa. It primarily infects African hippopotamuses and has a more limited host range compared to other Schistosoma species.

References

  1. 1 2 3 4 Buckley JJC (1939). "Observations on Gastrodiscoides hominis and Fasciolopsis in Assam". Journal of Helminthology. 17 (1): 1–12. doi:10.1017/S0022149X00030972. S2CID   83540770.
  2. 1 2 3 4 5 Mas-Coma S, Bargues MD, Valero MA (2006). "Gastrodiscoidiasis, a plant-borne zoonotic disease caused by the intestinal amphistome fluke Gastrodiscoides hominis (Trematoda: Gastrodiscidae)". Revista Ibérica de Parasitología. 66 (1–4): 75–81. ISSN   0034-9623. Archived from the original on 2014-05-03.
  3. 1 2 Kumar V (1980). "The digenetic trematodes, Fasciolopsis buski, Gastrodiscoides hominis and Artyfechinostomum malayanum, as zoonotic infections in South Asian countries". Ann Soc Belg Med Trop. 60 (4): 331–339. PMID   7016049.
  4. 1 2 3 4 Dada-Adegbola HO, Falade CO, Oluwatoba OA, Abiodun OO (2004). "Gastrodiscoides hominis infection in a Nigerian-case report". West African Journal of Medicine. 23 (2): 185–186. doi: 10.4314/wajm.v23i2.28116 . PMID   15287303.
  5. ↑ Murty CV, Reddy CR (1980). "A case report of Gastrodiscoides hominis infestation". Indian J Pathol Microbiol. 23 (4): 303–304. PMID   7228220.
  6. 1 2 3 4 5 6 Liu D (2012). Molecular Detection of Human Parasitic Pathogens. Boca Raton, FL: CRC Press. pp. 365–368. ISBN   978-1-4398-1242-6.
  7. 1 2 3 Müller R, Wakelin D (2001). Worms and Human Disease. CABI Publishing, Oxon, UK. pp. 55–56. ISBN   0851995160.
  8. 1 2 3 4 5 Khalil M (1923). "A description of Gastrodiscoides hominis, from the Napu mouse deer". Proceedings of the Royal Society of Medicine. 16 (1): 8–14. doi:10.1177/003591572301602102. PMC   2103306 . PMID   19983413.
  9. ↑ Leiper RT (1913). "Observations on certain helminths of Man". Transactions of the Royal Society of Tropical Medicine and Hygiene. 6 (8): 265–297. doi:10.1016/S0035-9203(13)90201-7.
  10. ↑ Buckley JJC (1964). "The problem of Gastrodiscoides hominis (Lewis and McConnell, 1876) Leiper, 1913". Journal of Helminthology. 38 (1–2): 1–6. doi:10.1017/S0022149X00033514. PMID   14125103. S2CID   19725197.
  11. ↑ Buckley JJC (1964). "The problem of Gastrodiscoides hominis (Lewis and McConnell, 1876) Leiper, 1913". Journal of Helminthology. 38 (1–2): 1–6. doi:10.1017/S0022149X00033514. PMID   14125103. S2CID   19725197.
  12. ↑ Tandon V, Maitra SC (1983). "Surface morphology of Gastrodiscoides hominis (Lewis & McConnell, 1876) Leiper, 1913 (Trematoda: Digenea) as revealed by scanning electron microscopy". Journal of Helminthology. 57 (4): 339–342. doi:10.1017/s0022149x00011056. PMID   6668422. S2CID   33543423.
  13. 1 2 Baker DG (2008). Flynn's Parasites of Laboratory Animals (2 ed.). Blackwell Publishers. p. 703. ISBN   978-0470344170.
  14. ↑ Brennan GP, Hanna RE, Nizami WA (1991). "Ultrastructural and histochemical observations on the tegument of Gastrodiscoides hominis (Paramphistoma: Digenea)". International Journal for Parasitology. 21 (8): 897–905. doi:10.1016/0020-7519(91)90164-3. PMID   1787030.
  15. ↑ Tandon V, Maitra SC (1983). "Surface morphology of Gastrodiscoides hominis (Lewis & McConnell, 1876) Leiper, 1913 (Trematoda: Digenea) as revealed by scanning electron microscopy". Journal of Helminthology. 57 (4): 339–342. doi:10.1017/s0022149x00011056. PMID   6668422. S2CID   33543423.
  16. ↑ Dutt SC, Srivastava HD (1966). "The intermediate host and the cercaria of Gastrodiscoides hominis (Trematoda: Gastrodiscidae). Preliminary report". Journal of Helminthology. 40 (1–2): 45–52. doi:10.1017/s0022149x00034076. PMID   5961529. S2CID   27860542.
  17. ↑ Dutt SC, Srivastava HD (1972). "The life history of Gastrodiscoides hominis (Lewis and McConnel, 1876) Leiper, 1913--the amphistome parasite of man and pig". Journal of Helminthology. 46 (1): 35–46. doi:10.1017/S0022149X00022100. PMID   5038423. S2CID   40322170.
  18. ↑ Dutt SC, Srivastava HD (1972). "The life history of Gastrodiscoides hominis (Lewis and McConnel, 1876) Leiper, 1913--the amphistome parasite of man and pig". Journal of Helminthology. 46 (1): 35–46. doi:10.1017/S0022149X00022100. PMID   5038423. S2CID   40322170.
  19. ↑ Chai JY, Shin EH, Lee SH, Rim HJ (2009). "Foodborne intestinal flukes in Southeast Asia". The Korean Journal of Parasitology. 47 (Suppl): 69–102. doi:10.3347/kjp.2009.47.S.S69. PMC   2769220 . PMID   19885337.
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