Bulinus spp. and Physopsis spp. reside. (Roberts and Janovy, 2000)can be found in Africa and the Middle East and southern Europe. can be found in areas where their intermediate hosts such as
has a very complex life cycle that is different from most other digenean life cycles. is distinct from many trematodes in that the sexes are separate in this species. Both male and females must remain together for long periods of time in order for the males to fertilize the females. This process can be difficult while the worms are inside the host's body since the males have to find the females in order to copulate.
According to experimental tests snail intermediate host, (Bulinus spp.) miracidia penetrate the snail and shed their epithelia. Miracidia without epithelial tissue are called sporocysts. Next, the sporocysts produced daughter sporocysts. The sporocyst grows by absorbing the host tissue, then the germinal cells divide and produce embryos that grow into daughter sporocysts. According to most digenean life cycles, most species will now produce rediae. Although most digenean sporocysts asexually produce a second immature from termed a redia neglects this stage and no rediae are formed.eggs increase their hatching time upon the dilution of urine in water. Eggs found to hatch 5 minutes after dilution of the urine continue to do so after 10-15 min. Hatching time increases under light and with vibration or disturbance of the eggs. Eggs then hatch into miracidia(larval stage) that have ciliated epithelia and swim in water. After finding the
Next, the sporocyst asexually produces the next immature form termed cercariae with tails that leave the snail host in order to find a definitive host. The cercariae burrow into the skin and lose their tails causing a condition called "Swimmer's Itch." Studies show that at temperatures under 10°C and over 40°C, cercariae do not develop properly and demonstrate a significant increase in their mortality. Preferable conditions for penetration of the skin would be between these extremes. Inside the host, the cercariae shed their tails and migrate to the liver via the host's circulatory system. The cercariae will feed on blood in the vessels until they reach their adult form. From the liver (Agnew, et al., 1988; Ghandour, 1976; Matsunaga, et al., 1987; Roberts and Janovy, 2000)travels to the bladder (venus plexus) where they begin to produce eggs. Egg formation occurs about 9.5 weeks after infestation.
Human infection occurs when the definitive host comes into contact with water containing cercariae released from snails infected with . The cercariae then burrow into the skin, spread, grow, and reproduce. Over the next few days the eggs are passed through the urine of the host. Traveling from the intermediate host to the definitive host is a complicated process. By separating the sexes the species must ensure that both male and female cercariae reach the host in order to reproduce, thus risking the chances of survival. (Basch, 1991)
Bristles and small spines probably act as tactile receptors, and these animals also may have reduced chemoreceptors. (Brusca and Bruca, 2003)
Adult (Basch, 1991)feeds on blood located in the veins around the urinary bladder of their mammalian host.
These animals are probably not preyed on directly but are ingested. Egg and larval mortality are high since the parasites often do not reach appropriate hosts.
is the cause of schistosomiasis also known as Bilharzia. Hosts of the parasite are humans. Schistosomiasis affects 200 million people worldwide and is considered one the most serious pathogenic infections today.
is pathogenic to humans and causes blood in the and urine and sometimes in the stool. Persons affected by may also develop cough, fever, skin inflammation, and tenderness of the liver because the spined eggs attach to vital organs and cause tissue degeneration. Later stages of the disease may be characterized by the swelling and damaging of the bladder, liver, and other organs. The eggs of can clog the bladder neck and cause infection. Many researchers have also observed damage on other body structures. Chronic schistosomiasis raises the incidence of bladder cancer in many Middle Eastern countries.
Drugs are available to cure Schistomiasis although the treatment process is long and unpleasant. Praziquantel is the leading drug in America In other nations, including Africa, Trichlorfon is administered. Unfortunately once the bladder wall is infested with eggs and feeding Schistosomes, prognosis is poor and the chances of surviving are slim. (Liese, 1986; Roberts and Janovy, 2000)
is not an ecologically endangered species. It is found abundantly throughout its normal habitats.
is a medically important parasite since bladder damage can lead to death. Calcified eggs embedded in the bladder wall increase the chances of blockage of the vessels. Although other species of Schistosoma also cause medical problems, is the only species that affects the human urinary system.
Renee Sherman Mulcrone (editor).
Janki Trivedi (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
uses smells or other chemicals to communicate
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
having the capacity to move from one place to another.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
scrub forests develop in areas that experience dry seasons.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
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Anwar, M. 1962. Ciba Foundation Symposium Bilharziasis. Boston: Little Brown Company.
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Brusca, R., G. Bruca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..
Ghandour, A. 1976. A study of the relationship between temperature and the infectivity of Schistosoma mansoni and Schistosoma haematobium cercariae. Journal of Helminthology, 50: 193-6.
Liese, B. 1986. The Organization of Schistosomiasis Control Programmes. Parasitology Today, 2: 339-340.
Matsunaga, K., H. Nojima, D. Koech. 1987. Dependence of hatching of Schistosoma haematobium miracidia on physical and biological factors.. Parasitology Research, 74: 55-60.
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