Schistosoma is a genus of trematodes, commonly known as blood flukes. They are parasitic flatworms responsible for a highly significant group of infections in humans termed schistosomiasis, which is considered by the World Health Organization as the second-most socioeconomically devastating parasitic disease (after malaria), with hundreds of millions infected worldwide.
Adult flatworms parasitize blood capillaries of either the mesenteries or plexus of the bladder, depending on the infecting species. They are unique among trematodes and any other flatworms in that they are dioecious with distinct sexual dimorphism between male and female. Thousands of eggs are released and reach either the bladder or the intestine (according to the infecting species), and these are then excreted in urine or feces to fresh water. Larvae must then pass through an intermediate snail host, before the next larval stage of the parasite emerges that can infect a new mammalian host by directly penetrating the skin.
The origins of this genus remain unclear. For many years it was believed that this genus had an African origin, but DNA sequencing suggests that the species (S. edwardiense and S. hippopotami) that infect the hippo (Hippopotamus amphibius) could be basal. Since hippos were present in both Africa and Asia during the Cenozoic era, the genus might have originated as parasites of hippos. The original hosts for the South East Asian species were probably rodents.
Based on the phylogenetics of the host snails it seems likely that the genus evolved in Gondwana between and .
The sister group to Schistosoma is a genus of elephant-infecting schistosomes — Bivitellobilharzia.
The cattle, sheep, goat and cashmere goat parasite Orientobilharzia turkestanicum appears to be related to the African schistosomes. This latter species has since been transferred to the genus Schistosoma.
Within the haematobium group S. bovis and S. curassoni appear to be closely related as do S. leiperi and S. mattheei.
S. mansoni appears to have evolved in East Africa 0.
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Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schistosomes reside in blood vessels. Some parasitic worms, including leeches and monogeneans, are ectoparasites - thus, they are not classified as helminths, which are endoparasites. Parasitic worms live in and feed in living hosts.
Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete worms (bristle worms); for the African giant earthworm, Microchaetus rappi; and for the marine nemertean worm (bootlace worm), Lineus longissimus. Various types of worm occupy a small variety of parasitic niches, living inside the bodies of other animals.
Trematoda is a class of flatworms known as flukes or trematodes. 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, where the flukes sexually reproduce, is a vertebrate. Infection by trematodes can cause disease in all five traditional vertebrate classes: mammals, birds, amphibians, reptiles, and fish. Trematodes are commonly referred to as flukes.
Molecular dynamics (MD) simulations have emerged as a transformative approach to analyse molecular systems at the atomic level, offering valuable insights into complex biological processes. Many biological phenomena can only accurately be described by inco ...
EPFL2023
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The ecology of the aquatic snails that serve as obligatory intermediate hosts of human schistosomiasis is driven by climatic and hydrological factors which result in specific spatial patterns of occurrence and abundance. These patterns in turn affect, join ...
2019
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Background Despite their importance for designing and evaluating schistosomiasis control trials, little attention in the literature has been dedicated to sampling protocols for the parasite's snail intermediate hosts since their first development. We propo ...