Echinostoma
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,[2] and a variety of animals, including humans, as their definitive hosts.
Echinostoma infect the gastrointestinal tract of humans, and can cause a disease known as echinostomiasis. The parasites are spread when humans or animals eat infected raw or undercooked food, such as bivalve molluscs or fish. [3]
There has been debate about the number of species in this group, with estimates as high as 120 unique species of Echinostoma,[4] however, currently 16 species have been accepted as valid species with another 10 to be validated [5]Echinostoma are difficult to classify based on morphology alone. Many species look alike and can be considered cryptic species (different lineages are considered to be the same species, due to high morphological similarity between them).[6] Many species of Echinostoma have been re-classified several times. For example, the species now known as Echinostoma caproni, was previously known by a variety of names including E. liei, E. parasensei and E. togoensis.[4]
Methods for classifying Echinostoma species, such as the Echinostoma revolutum group, were devised by Kanev.[7] The Echinostoma species in this group are now classified according to their shared morphological and biological characteristics, such as the presence of 37 collar spines.[7]
Molecular methods, such as sequencing mitochondrial DNA and ribosomal DNA, are also used to distinguish between species of Echinostoma as an alternative to morphological classification methods.[8]
Further confirmed species are E. lindoense Sandground & Bonne, 1940 and E. luisreyi Maldonado, Vieira & Lanfredi, 2003, these are not included in the phylogeny because of a lack of genetic material.[5] Unconfirmed species are E. acuticauda, E. barbosai, E. chloephagae, E. echinatum, E. jurini, E. nudicaudatum, E. parvocirrus, E. pinnicaudatum, E. ralli, and E. rodriguesi.[5]
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