''Echinostoma revolutum'' is a

trematode Trematoda is a class of flatworms known as flukes. 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 ...

parasites, of which the adults can infect

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

and

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

, including humans. In humans, it causes echinostomiasis..

Distribution

''Echinostoma revolutum'' is the most widely distributed species of the known 20 Echinostomatidae species; it is found in Asia, Oceania, Europe, and the Americas. In Asian countries the disease is endemic to humans. Outbreaks have been reported in North America after travellers returend from

Kenya ) , national_anthem = "Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi , ...

and

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...

Description

The worms are leaflike, elongated, and an average of 8.8 mm long (8.0–9.5 mm) and 1.7 mm wide (1.2–2.1 mm). When first passed in the feces, they were pinkish red and coiled in a "c" or "e" shape. The eggs in

uteri The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uteru ...

were an average of 105 μm long (97–117 μm) and 63 μm wide (61–65 μm).

Life cycle

Infection of ''Echinostoma revolutum'' usually results from ingestion of raw snails or frogs that serve as an intermediate host. This parasite is predominantly found throughout

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. Two asexual generations occur in a snail or mollusc. The first snail host is penetrated by a

miracidium The Miracidium is the second stage in the life cycle of trematodes. When trematode eggs are laid and come into contact with fresh water, they hatch and release miracidium. In this phase, miracidia are ciliated and free-swimming. This stage is com ...

, producing a sporocyst. Many sporocysts are produced and mother rediae emerge. Mother rediae asexually reproduce daughter rediae, which also multiply. Each rediae then develop into a cercariae, which penetrates a second host. The second host could be another snail or a tadpole, in which development into metacercaria occurs. Cercariae typically find a snail host through

chemotaxis Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemica ...

. The cercariae are attracted to the slime of the snail, which contains small peptides. The first larval stage is the miracidium, and are found to be attracted to macrocmolecular

glycoconjugates Glycoconjugates are the classification family for carbohydrates – referred to as glycans – which are covalently linked with chemical species such as proteins, peptides, lipids, and other compounds. Glycoconjugates are formed in processes term ...

associated with a possible snail host. Environmental stimuli such as light and gravity can also be used to assist in searching for a host.

Intermediate hosts

Intermediate hosts of ''Echinostoma revolutum'' include: * ''

Anentome helena ''Anentome helena'', common name assassin snail or bumblebee snail, is a species of freshwater snail with an operculum, an aquatic gastropod in the family Nassariidae, most of which are marine. Distribution The assassin snail is found throu ...

'' (formerly ''Clea helena'') * '' Bithynia funiculata'' * '' Bithynia siamensis siamensi'' * '' Corbicula producta'' * ''

Eyriesia eyriesi ''Eyriesia'' is a genus of freshwater snail Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the l ...

'' * '' Filopaludina sumatrensis polygramma'' * '' Filopaludina martensi martensi'' * '' Filopaludina'' spp. * '' Idiopoma doliaris'' (formerly ''Filopaludina doliaris'') * ''

Lymnaea stagnalis ''Lymnaea stagnalis'', better known as the great pond snail, is a species of large air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Lymnaeidae. The great pond snail is a model organism to study parasitology, ...

'' * ''

Lymnaea ''Lymnaea'' is a genus of small to large-sized air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the subfamily Lymnaeinae ( of the family Lymnaeidae, the pond snails.Bouchet, P.; Rosenberg, G. (2013). Lymnaea Lamarck, 179 ...

'' sp. in Thailand * '' Physa occidentalis'' * ''

Radix auricularia ''Radix auricularia'', the big-ear radix, is a species of medium-sized freshwater snail, an aquatic pulmonate gastropod mollusk in the family Lymnaeidae.Neubauer, Thomas A.; Rosenberg, G.; Gofas, S. (2014). Radix auricularia (Linnaeus, 1758) ...

'' accessed 22 October 2008

In humans

In Pursat Province,

Cambodia Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailand t ...

, children eating undercooked snails or clams were identified as a possible source of infection in humans.

Prevalence

The first reported human infection was in

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

in 1929. The

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

of ''Echinostoma revolutum'' trematodes in Taiwan during 1929–1979 varied from 0.11% to 0.65%. Small ''Echinostoma revolutum''– endemic foci or a few cases of human infection were discovered in the People's Republic of China, Indonesia, and Thailand until 1994. However, no information is available about human ''Echinostoma revolutum'' infection after 1994, even in areas where the parasite was previously endemic. In 2007 prevalence of ''E. revolutum'' adults in school children in Pursat Province,

ranged from 7.5% to 22.4%. Authors reported echinostomiasis as an endemic trematode infection among schoolchildren in Pursat.

Symptoms

Signs of infection in humans due to this type of fluke can result to weakness and emaciation. In cases where infection is heavy, hemorrhagic enteritis can occur.

Diagnosis

''Echinostoma revolutum'' could be detected through observing feces containing eggs under a microscope.

Prevention

Treatment

Albendazole Albendazole (also known as albendazolum) is a broad-spectrum anthelmintic and antiprotozoal agent of the benzimidazole type. It is used for the treatment of a variety of intestinal parasite infections, including ascariasis, pinworm infection, h ...

and

praziquantel Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of helminthiasis, parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is us ...

are typically prescribed to rid the parasite from the body.