In recent surveys of conversion disorder (formerly classified as "hysterical neurosis, conversion type"), females predominate, with between two and six female patients for every male but some research suggests this gender disparity may be confounded by higher rates of violence against women. Age
Conversion disorder may present at any age but is rare in children younger than ten or in the elderly. Studies suggest a peak onset in the mid-to-late 30s. History
The first evidence of functional neurological symptom disorder dates back to 1900 BC, when the symptoms were blamed on the uterus moving within the female body. The treatment varied "depending on the position of the uterus, which must be forced to return to its natural position. If the uterus had moved upwards, this could be done by placing malodorous and acrid substances near the womans mouth and nostrils, while scented ones were placed near her vagina; on the contrary, if the uterus had lowered, the document recommends placing the acrid substances near her vagina and the perfumed ones near her mouth and nostrils. "In Greek mythology, hysteria, the original name for functional neurological symptom disorder, was thought to be caused by a lack of orgasms, uterine melancholy and not procreating. Plato, Aristotle and Hippocrates believed a lack of sex upsets the uterus. The Greeks believed it could be prevented and cured with wine and orgies.
T. nativa, which has a high resistance to freezing, is found in the Arctic and subarctic regions; reservoir hosts include polar bears, Arctic foxes, walruses, and other wild game. T. nelsoni, found in East African predators and scavengers, has been documented to cause a few human cases. T. papuae infects both mammals and reptiles, including crocodiles, humans, and wild and domestic pigs; this species, found in Papua New Guinea and Thailand, is also nonencapsulated. T. pseudospiralis infects birds and mammals, and has demonstrated infection in humans; it is a nonencapsulated species. T. zimbabwensis can infect mammals, and possibly humans; this nonencapsulated species was detected in crocodiles in Africa. Taxonomy
Kingdom: Animalia
Phylum: Nematoda
Class: Adenophorea
Order: Trichurida
Family: Trichinellidae
Genus: Trichinella

Lifecycle
The typical lifecycle for T. spiralis involves humans, pigs, and rodents. A pig becomes infected when it eats infectious cysts in raw meat, often porcine carrion or a rat (sylvatic cycle). A human becomes infected by consuming raw or undercooked infected pork (domestic cycle). In the stomach, the cysts from infected undercooked meat are acted on by pepsin and hydrochloric acid, which help release the larvae from the cysts into the stomach. The larvae then migrate to the small intestine, and burrow into the intestinal mucosa, where they molt four times before becoming adults.Thirty to 34 hours after the cysts were originally ingested, the adults mate, and within five days produce larvae. Adult worms can only reproduce for a limited time, because the immune system eventually expels them from the small intestine.