Schistosoma mansoni is one of the three main Schistosoma trematode flatworms that infect humans and cause schistosomiasis (=bilharziasis), the other two being S. haematobium and S. japonicum (in some regions, S. mekongi and S. intercalatum also infect humans and cause schistosomiasis). Other schistosome species, which parasitize birds and non-human mammals, can cause cercarial dermatitis in humans.

The life cycle of S. mansoni and related schistosomes is complex. Eggs are eliminated from a human host with feces or urine. Under optimal conditions, the eggs hatch and release miracidia, which swim and penetrate specific snail intermediate hosts. The life stages within the snail include two generations of sporocysts and the production of cercariae. Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host, and shed their forked tail, becoming schistosomulae (human contact with water is thus necessary for infection by schistosomes). The schistosomulae migrate through several tissues and stages to their residence in the veins. Adult worms in humans reside in the mesenteric venules in various locations, which at times seem to be specific for each species. For example, S. japonicum is more frequently found in the superior mesenteric veins draining the small intestine and S. mansoni occurs more often in the superior mesenteric veins draining the large intestine. However, both species can occupy either location, and they are capable of moving between sites, so it cannot be stated unequivocally that either is found only in one location or another. Schistosoma haematobium most often occurs in the venous plexus of bladder, but can also be found in the rectal venules. The females (7 to 20 mm in length, slightly larger than males) deposit eggs in the small venules of the portal and perivesical systems. The eggs are moved progressively toward the lumen of the intestine (S. mansoni and S. japonicum) and of the bladder and ureters (S. haematobium), and are eliminated with feces or urine, respectively.

Pathology of S. mansoni schistosomiasis includes: Katayama fever, hepatic perisinusoidal egg granulomas, Symmers' pipe stem periportal fibrosis, portal hypertension, and occasional embolic egg granulomas in brain or spinal cord.

Schistosoma mansoni is found in parts of South America and the Caribbean, Africa, and the Middle East.

(Source: Centers for Disease Control Parasites and Health Website)

Schistosoma mansoni is a trematode flatworm, one of a number of species of schistosome causing the parasitic disease schistosomiasis, or Bilharzia. Schistosomiasis affects over 200 million people worldwide.

• Urinary schistosomiasis - parasites progressively damaging the bladder, ureters and kidneys.
• Intestinal schistosomiasis - parasites progressively enlarging the liver and spleen, damaging the intestine and causing hypertension of the abdominal blood vessels.

Drug treatment, snail control, improved sanitation and health education are being used to try and control schistosomiasis.

Schistosoma mansoni is a parasite that is found in Africa, Madagascar, parts of South America (such as Venezuela and Brazil), Puerto Rico and the West Indies.

Biogeographic Regions: ethiopian (Native ); neotropical (Native )

Schistosoma mansoni is found in many African countries, and some areas of South America, the Caribbean and Middle East.

Habitat
Schistosoma mansoni is a parasitic organism. Different stages of the life cycle live in different hosts

• Adults live in human blood vessels
• Miracidium live for a short time in fresh water before infecting snails
• Cercariae develop in the snail and are released in to freshwater before infecting humans.

During its lifetime, this parasite lives in the bodies of two different hosts. The first, the intermediate host, is usually a freshwater snail from the family Planorbidae. The ciliated larvae mature into sporocysts in these snails, making the snail a producer of cercariae for the remainder of its life. Adults mature and reproduce in the mesenteric portal system of a wide variety of hosts such as man, mice and hamsters. They thrive in tropical and equatorial environments because there are more people and a wide range of molluscs to act as hosts, as well as many rivers to transfer and carry the miracidia and cercariae.

Aquatic Biomes: lakes and ponds; rivers and streams

Shistosomula (the tail-less larvae of the worm) mature and reproduce in the hepatic portal system of their definitive (final) host. The blood in this system is rich in soluble food materials such as amino acids and monosaccharides. The shistosome worms ingest blood from the hepatic and mesenteric veins. Females feed more actively than males because the nutritional requirements of egg production are much greater than the nutritional requirements needed for sperm production.

Schistosoma mansoni is one of the major causes of the disease schistosomiasis.The symptoms, extent and severity of the disease depend on the number of adult schistosome pairs because the eggs laid by each female cause the pathology.

• Eggs that do not pass through the wall of the intestine are circulated in the blood. Initially the eggs may produce a fever (Katayama fever), but symptoms may be hard to recognise.
• Eggs trapped in the liver cause an immune response that damages the liver over time and cause further severe complications.
• Eggs lodged in the intestine wall can cause a reaction leading to intestine blockage and blood loss.

Schistosomiasis can be diagnosed by looking for eggs in stools using a microscope. Blood tests are also available.Schistosomiasis is usually treated with the drug Praziquantel, which is effective in killing adult schistosomes.

Adults
Mature adult Schistosoma mansoni are about 1 cm long. The male and female form a reproductive pair, with the female held by the male within a groove. Females release eggs, into the blood vessels. A pair may live for years within the host, the female producing thousands of eggs during this time.

Eggs

• passed out through the wall of the host's intestine.
• circulating in the blood cause much of the pathology associated with schistosomiasis, as they become trapped in the liver and other internal organs.

The eggs in the intestine pass out of the body with faeces and if they come into contact with fresh water, hatch into a free-living life-cycle stage called the miracidium.

Miracidium stage

• swim about in the water, propelled by the many cilia that cover them.
• never feed
• live for about a day

Miracidia must locate and infect another host freshwater snails (genus Biomphalaria) to continue the life-cycle. Within the snail, a miracidium transforms into a sporocyst – a factory for producing the next life-cycle stage, the cercaria.

Cercaria stage
The spororcyst produces cercariae through asexual reproduction, so that one miracidium can produce many thousands of genetically identical cercariae. Somewhere around 3-4 weeks after being infected, the snail begins to shed cercariae into the water. Like miracidia, cercariae

• do not feed
• live for about a day
• propel themselves with an actively
  beating tail, swimming tail-first through the water.

The cercaria is the stage that infects humans. Cercariae infect their human host by penetrating through the skin. In about a month, the cercariae have developed into mature schistosomes that have formed pairs, migrated to the blood vessels around the intestine and have begun to produce eggs.

Schistosoma mansoni are a unusual among flatworms because they are dioecious (separate sexes). The male is much larger and broader than the female and the female fits into a groove in his body. Copulation takes place in the veins of the liver and mesentery, and they copulate quite frequently. The female lays eggs in the small veins without leaving her mate. The eggs are unique and easily identifiable because of the singular spine that they possess on the lateral side of the egg. The female can lay about 300 eggs per day. There is also a sporocyst stage in the larval stage of the life cycle of S. mansoni, which allows it to produce a very large quantity of offspring from a single zygote.

The following is a representative barcode sequence, the centroid of all available sequences for this species. 

 
There are 38 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
 

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 20
Species: 33
Species With Barcodes: 1

The recovery of eggs from a 5,000 year old Egyptian mummy has shown that the disease, schistosomiasis, caused by this parasite has been present since prehistoric times. The recent report of newly discover strains illustrates the continuing versatality of these parasites.

In countries affected by Schistosoma mansoni, such as Egypt, where the climate is very dry, agricultural development is hindered because they can not irrigate the land. The most detrimental effect of the parasite, however, is schistosomiasis. It occurs in many third world or underdeveloped countries, and it has a serious negative economic impact. The disease spreads rapidly people are ignorant of the danger of the parasite and the disease caused by it. The disease not only affects humans but animals and lifestock as well. Animals are needed for their meat as well as for manual labor for farmers. When the disease afflicts animals, human food sources are affected as well. Another negative effect of the parasite is that the government must put a substantial amount of funding into the purification of water. This can be a time consuming and expensive project if it is possible at all

Research in the area of contolling this parasite is a major source of income. Many governmental research laboratories in the countries affected by this parasite, such as the National Research Center in Dokki, Egypt, focus on schistosomiasis. Because schistosomiasis is so easily spread through contact with contaminated water, the water in the countries affected by the disease is virtually unusable. This provides an industry centered around water purification andthe production of bottled, purified water.