Editing Flatworm (section)

===Parasitism===

[[File:Neurocysticercosis.gif|thumb |Magnetic resonance image of a patient with [[neurocysticercosis]] demonstrating multiple [[Cestoda|cysticerci]] of the pork tapeworm ''[[Taenia solium]]'' within the brain]]

[[Cestode]]s (tapeworms) and [[digenea]]ns (flukes) cause diseases in humans and their [[livestock]], whilst [[monogenea]]ns can cause serious losses of stocks in [[fish farm]]s.<ref name="NorthropClewesShaw2000Parasites" /> [[Schistosomiasis]], also known as bilharzia or snail fever, is the second-most devastating parasitic disease in tropical countries, behind [[malaria]]. The [[Carter Center]] estimated 200&nbsp;million people in 74 countries are infected with the disease, and half the victims live in Africa. The condition has a low [[mortality rate]], but usually presents as a [[chronic illness]] that can damage internal organs. It can impair the growth and [[cognitive development]] of children, increasing the risk of [[bladder cancer]] in adults. The disease is caused by several flukes of the genus ''[[Schistosoma]]'', which can bore through human skin; those most at risk use infected bodies of water for recreation or [[laundry]].<ref name="SCP">{{Cite web|author=The Carter Center|title=Schistosomiasis Control Program|url=http://www.cartercenter.org/health/schistosomiasis/index.html|access-date=2008-07-17|archive-date=2008-07-20|archive-url=https://web.archive.org/web/20080720091015/http://cartercenter.org/health/schistosomiasis/index.html|url-status=live}}</ref>

In 2000, an estimated 45&nbsp;million people were infected with the beef tapeworm ''[[Taenia saginata]]'' and 3&nbsp;million with the pork tapeworm ''[[Taenia solium]]''.<ref name="NorthropClewesShaw2000Parasites" /> Infection of the digestive system by adult tapeworms causes abdominal symptoms that, whilst unpleasant, are seldom disabling or life-threatening.<ref>{{cite journal |author1=García, H.H. |author2=Gonzalez, A.E. |author3=Evans, C.A.W. |author4=Gilman, R.H. |title=''Taenia solium'' cysticercosis |journal=The Lancet |volume=362 |issue=9383|year=2003|pages=547–556 |doi=10.1016/S0140-6736(03)14117-7 |pmid=12932389 |pmc=3103219 }}</ref><ref>{{cite journal |author=WHO Expert Committee |title=Public health significance of intestinal parasitic infections |journal=Bulletin of the World Health Organization |volume=65 |issue=5 |pages=575–588 |year=1987 |url=http://whqlibdoc.who.int/bulletin/1987/Vol65-No5/bulletin_1987_65(5)_575-588.pdf |access-date=2008-12-24 |pmid=3501340 |pmc=2491073 |archive-url=https://web.archive.org/web/20090816023000/http://whqlibdoc.who.int/bulletin/1987/Vol65-No5/bulletin_1987_65(5)_575-588.pdf |archive-date=2009-08-16 |url-status=dead }}</ref> However, [[neurocysticercosis]] resulting from penetration of ''T. solium'' larvae into the [[central nervous system]] is the major cause of acquired [[epilepsy]] worldwide.<ref>{{cite journal |author=Commission on Tropical Diseases of the International League Against Epilepsy |title=Relationship Between Epilepsy and Tropical Diseases |journal=Epilepsia |volume=35 |issue=1 |pages=89–93 |year=1994 |doi=10.1111/j.1528-1157.1994.tb02916.x |pmid=8112262 |s2cid=221733822 }}</ref> In 2000, about 39&nbsp;million people were infected with [[trematode]]s (flukes) that naturally parasitize fish and crustaceans, but can pass to humans who eat raw or lightly cooked seafood. Infection of humans by the broad fish tapeworm ''[[Diphyllobothrium latum]]'' occasionally causes [[vitamin B12|vitamin B<sub>12</sub>]] deficiency and, in severe cases, [[megaloblastic anemia]].<ref name="NorthropClewesShaw2000Parasites" />

The threat to humans in developed countries is rising as a result of social trends: the increase in [[organic farming]], which uses [[manure]] and [[sewage sludge]] rather than artificial [[fertilizer]]s, spreads parasites both directly and via the droppings of [[seagull]]s which feed on manure and sludge; the increasing popularity of raw or lightly cooked foods; imports of meat, [[seafood]] and [[salad]] vegetables from high-risk areas; and, as an underlying cause, reduced awareness of parasites compared with other [[public health]] issues such as [[pollution]]. In less-developed countries, inadequate sanitation and the use of human [[feces]] (night soil) as fertilizer or to enrich fish farm ponds continues to spread parasitic platyhelminths, whilst poorly designed water-supply and [[irrigation]] projects have provided additional channels for their spread. People in these countries usually cannot afford the cost of fuel required to cook food thoroughly enough to kill parasites. Controlling parasites that infect humans and livestock has become more difficult, as many species have become [[Drug resistance|resistant]] to drugs that used to be effective, mainly for killing juveniles in meat.<ref name="NorthropClewesShaw2000Parasites">{{cite journal |author1=Northrop-Clewes, C.A. |author2=Shaw, C. |title=Parasites |journal=British Medical Bulletin |volume=56 |pages=193–208 |year=2000 |doi=10.1258/0007142001902897 |pmid=10885116 |issue=1 |doi-access=free }}</ref> While poorer countries still struggle with unintentional infection, cases have been reported of intentional infection in the US by dieters who are desperate for rapid weight-loss.<ref>{{cite news |url=http://www.today.com/health/iowa-woman-tries-tapeworm-diet-prompts-doctor-warning-6C10935746 |title=Iowa woman tries 'tapeworm diet', prompts doctor warning |work=[[Today (U.S. TV program)]] |date=2013-08-16 |access-date=2013-09-22 |archive-date=2017-11-07 |archive-url=https://web.archive.org/web/20171107112623/https://www.today.com/health/iowa-woman-tries-tapeworm-diet-prompts-doctor-warning-6C10935746 |url-status=live}}</ref>