Worms #1.

Pinworms
Causal Agent: The nematode (roundworm) Enterobius vermicularis (previously Oxyuris vermicularis) also called human pinworm. (Adult females: 8 to 13 mm, adult male: 2 to 5 mm.) Humans are considered to be the only hosts of E. vermicularis. A second species, Enterobius gregorii, has been described and reported from Europe, Africa, and Asia. For all practical purposes, the morphology, life cycle, clinical presentation, and treatment of E. gregorii is identical to E. vermicularis.

Eggs are deposited on perianal folds [1] . Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area [2]. Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g., curtains, carpeting). Some small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs. Following ingestion of infective eggs, the larvae hatch in the small intestine [3] and the adults establish themselves in the colon [4]. The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months. Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area [5]. The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions [1]. Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown.

Geographic Distribution: Worldwide, with infections more frequent in school- or preschool- children and in crowded conditions. Enterobiasis appears to be more common in temperate than tropical countries. The most common helminthic infection in the United States (an estimated 40 million persons infected). (Above courtesy of Centers for Disease Control)

Pinworm. Adult female worms of Enterobius vermicularis collected from a 2-year-old girl in a Korean orphanage after treatment with pyrantel pamoate 10 mg/kg, November 24, 1975.
(Courtesy of www.emedicine.com/med/topic1837.htm).

Complications : Typical pinworm infections don't cause serious problems. In rare circumstances, complications can develop from a heavy infection, including:

• Urinary tract infection. More common in females, urinary tract infections sometimes are caused by heavy pinworm infestation. The parasite can also migrate to the bladder, causing cystitis.
  
• Infection of the peritoneal cavity. In women or girls, the parasite may travel from the anal area up the vagina to the uterus, fallopian tubes and the area around the pelvic organs. This can cause vaginitis, endometritis or other problems.
  
• Dientamoeba fragilis infection. This parasite, which lives in human intestines, is often spread through contaminated food or water. Although scientists are not sure, it appears that you also may be able to contract this parasite by swallowing pinworm eggs — which may contain the fragile parasite. Signs and symptoms include diarrhea, abdominal cramping, weight loss, loss of appetite and fatigue. You can prevent pinworm-related infection by washing your hands frequently and thoroughly to make sure you don't swallow pinworm eggs that may be on your hands.
  
• Weight loss. When a large number of adult pinworms are living in your intestine, they can cause enough abdominal pain and take enough nutrients that you will lose weight.

(Courtesy of MayoClinic.com)