Echinostoma revolutum is a trematode parasite of which the adults can infect birds and mammals, including humans. In humans, it causes echinostomiasis.
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 returned from Kenya and Tanzania.
The worms are leaflike, elongated, and an average of 8.8 mm long (8.0âÂÂ9.5 mm) and 1.7 mm wide (1.2âÂÂ2.1 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 üm long (97âÂÂ117 üm) and 63 üm wide (61âÂÂ65 üm).
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. Two asexual generations occur in a snail or mollusc. 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 macromolecular 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.
Intermediate hosts of Echinostoma revolutum include:
The prevalence of Echinostoma revolutum trematodes in Taiwan, from the first reported human infection in 1929 through 1979, varied from 0.11% to 0.65%. Small clusters and individual cases of human infection were discovered in the People's Republic of China, Indonesia, and Thailand until 1994, after which no data is available. In 2007 a fecal survey in 4 primary schools in Pursat Province, Cambodia found an infection rate amongst students to be between 7.5% to 22.4%.
In Pursat Province, Cambodia, children eating undercooked snails or clams were identified as a possible source of infection in humans.
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.
Praziquantel is typically prescribed to rid the parasite from the body. Alternatively, mebandazole has been used to treat echinostomiasis. Albendazole has been reported to show effective results although without details on the dosage and cure rates.