Aquatic Parasite Observatory

Echinostoma spp. (Rudolphi, 1809)

    • Species Name: Echinostoma spp. (Rudolphi, 1809)
    • Synonyms: Fascioletta (Garrison, 1908); Metechinostoma (Petrochenko and Khrustaleva, 1963)
    • Taxonomy: (Rudolphi, 1809) Animalia, Platyhelminthes, Trematoda, Echinostomida, Echinostomidae, Echinostoma spp.
    • Life Cycle: “Many animals may serve as definitive hosts for various echinostome species, including aquatic birds, carnivores, rodents and humans. Unembryonated eggs are passed in feces and develop in the water. The miracidium takes on average 10 days to mature before hatching and penetrating the first intermediate host, a snail. Several genera of snails may serve as the first intermediate host. The intramolluscan stages include a sporocyst, one or two generations of rediae, and cercariae. The cercariae may encyst as metacercariae within the same first intermediate host or leave the host and penetrate a new second intermediate host. Depending on the species, several animals may serve as the second intermediate host, including other snails, bivalves, fish, and tadpoles. The definitive host becomes infected after eating infected second intermediate hosts. Metacercariae excyst in the duodenum and adults reside in the small intestine” (CDC).
    • Description:
      1. Body medium to large, elongate with maximum width level of ventral sucker or uterus. Forebody very short to short; hindbody dorsoventrally flattened, with almost parallel margins. Tegument armed with scale-like spines to level of anterior margin of ventral sucker dorsally and to level of posterior testis ventrally and laterally. Collar well developed, reniform; ventral ridge muscular. Collar-spines 31-55; lateral spines in single row; dorsal spines in double row; angle spines 2x5, longer than marginal spines. Oral sucker subspherical, small. Ventral sucker large with deep cavity, close to anterior extremity. Prepharynx short. Pharynx well developed. Oesophagus short. Testes tandem, elongate-oval, smooth indented or lobed, contiguous or separated, just postequatorial; occasionally, anterior testis equatorial. Cirrus-sac oval to elongate-oval, muscular, between intestinal bifurcation and posterior margin of ventral sucker dorsally. Internal seminal vesical large, with saccular posterior part and coiled tubular anterior part. Pars prostatica well developed. Ejaculatory duct long. Cirrus tubular, unspined. Ovary small, spherical, median, equatorial or just pre-equatorial. Mehlis' gland compact, similar in size to ovary. Uterus long to very long, with numerous loops. Metraterm muscular, long. Eggs abundant. Vitelline fields in hindbody, may approach median line posteriorly to testes but usually non-confluent, reach ventral sucker anteriorly; follicles small. Stem of excretory vesicle chambered or not; arms with lateral diverticula; pore terminal. In intestine of wide range of awuatic birds and mammals; cosmopolitan. Cercariae in freshwater pulmonate (Planorbidae, Lymnaeidae) and prosobranch (Viviparidae) gastropods; metacercariae in wide range of freshwater molluscs (Gastropoda, Bivalvia), planarians and tadpoles. Type species E. revolutum (Frolich, 1802) Rudolphi, 1809.
    • Sources: Jones, A., Bray, R.A., and Gibson, D.I. 2005. Keys to the Trematoda, Vol. 2.
    • APO Parasite Records: (by Life Cycle)

Parasite Images:

Distribution Map:

  • University of Colorado Boulder

  • University of Colorado Boulder