Echinostoma revolutum
Encyclopedia
Echinostoma revolutum is a fluke
that can be a parasite in humans. It causes the disease echinostomiasis.
Echinostomiasis is not only an endemic infectious disease in Asian countries, but also can be imported by overseas travelers from the United States or Europe. An outbreak of echinostomiasis was reported among US travelers returning from Kenya and Tanzania, although the source of infection was uncertain.
. Two asexual generations occur in a snail or mollusk. The first snail host is penetrated by a miracidium
, 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
. 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
associated with a possible snail host. Environmental stimuli such as light and gravity can also be used to assist in searching for a host.
Hosts of Echinostoma revolutum include:
For example in Pursat Province, Cambodia
the children were fond of eating undercooked snails or clams of unidentified species sold on the road to their homes after school. It was a source of infection in humans.
in 1929. The prevalence
of Echinostoma revolutum flukes 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. The prevalence of infection with Echinostoma revolutum flukes ranged from 7.5% to 22.4% in 4 schools surveyed in Pursat Province, Cambodia
, tested fecal specimens from 471 children, 10–14 years of age, in June 2007. Authors reported echinostomiasis as an endemic trematode infection among schoolchildren in Pursat.
and praziquantel
are typically prescribed to rid the parasite from the body.
Trematoda
Trematoda is a class within the phylum Platyhelminthes that contains two groups of parasitic flatworms, commonly referred to as "flukes".-Taxonomy and biodiversity:...
that can be a parasite in humans. It causes the disease echinostomiasis.
Distribution
Echinostoma revolutum is the most widely distributed species of all 20 Echinostomatidae species and it is found from Asia and Oceania to Europe and the Americas.Echinostomiasis is not only an endemic infectious disease in Asian countries, but also can be imported by overseas travelers from the United States or Europe. An outbreak of echinostomiasis was reported among US travelers returning from Kenya and Tanzania, although the source of infection was uncertain.
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 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 AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. Two asexual generations occur in a snail or mollusk. The first snail host is penetrated by a miracidium
Miracidium
Trematodes are small parasitic flatworms that use vertebrates as their definitive host, and molluscs as their intermediate host. In order to accomplish this, they have several varied lifecyle stages....
, 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
Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...
. 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
Glycoconjugates is the general classification for carbohydrates covalently linked with other chemical species.Glycoconjugates are very important compounds in biology and consist of many different categories such as glycoproteins, glycopeptides, peptidoglycans, glycolipids, and lipopolysaccharides...
associated with a possible snail host. Environmental stimuli such as light and gravity can also be used to assist in searching for a host.
Hosts of Echinostoma revolutum include:
- Physa occidentalis
- Lymnaea stagnalisLymnaea stagnalisLymnaea 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.-Distribution:The distribution of this species is Holarctic...
- LymnaeaLymnaeaLymnaea is a genus of small to large-sized air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Lymnaeidae, the pond snails.Lymnaea is the type genus of the family Lymnaeidae.-Species:...
sp. in Thailand - Radix auriculariaRadix auriculariaRadix auricularia, common name the big-ear radix, is a species of medium-sized freshwater snail, an aquatic pulmonate gastropod mollusk in the family Lymnaeidae.Radix auricularia is the type species of the genus Radix.-Forms:...
- Corbicula producta
For example in Pursat Province, Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
the children were fond of eating undercooked snails or clams of unidentified species sold on the road to their homes after school. It was a source of infection in humans.
Prevalence
The first reported human infection was in TaiwanTaiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
in 1929. The prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...
of Echinostoma revolutum flukes 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. The prevalence of infection with Echinostoma revolutum flukes ranged from 7.5% to 22.4% in 4 schools surveyed in Pursat Province, Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
, tested fecal specimens from 471 children, 10–14 years of age, in June 2007. 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.Treatment
AlbendazoleAlbendazole
Albendazole, marketed as Albenza, Eskazole, Zentel and Andazol, is a member of the benzimidazole compounds used as a drug indicated for the treatment of a variety of worm infestations. Although this use is widespread in the United States, the U.S. Food and Drug Administration has not approved...
and praziquantel
Praziquantel
Praziquantel is an anthelmintic effective against flatworms. Praziquantel is not licensed for use in humans in the UK; it is, however, available as a veterinary anthelmintic, and is available for use in humans on a named-patient basis....
are typically prescribed to rid the parasite from the body.