Amoebiasis

Most infected people, about 90%, are asymptomatic, but usually it is about two to four weeks. Symptoms can range from mild diarrhea to dysentery with blood, coupled with intense abdominal pains. Extra-intestinal complications might also arise as a result of invasive infection which includes colitis, liver, lung, or brain abscesses. The ingestion of one viable cyst may cause an infection. Steroid therapy can occasionally provoke severe amoebic colitis in people with any E. histolytica infection. This bears high mortality: on average more than 50% with severe colitis die. ==Cause==

Amoebiasis is an infection caused by the amoeba Entamoeba histolytica. Transmission '' Amoebiasis is usually transmitted by the fecal-oral route, Amoebic dysentery is one form of traveler's diarrhea. It is more prevalent in long-term travelers with stays of longer than six months as opposed to travelers who spend less than one month in an endemic area. Diarrhea caused by a parasite such as E. histolytica is more likely to have subacute or chronic characteristics. == Pathogenesis ==

Amoebiasis results from tissue destruction induced by the E. histolytica parasite. E. histolytica causes tissue damage by three main events: direct host cell killing, inflammation, and parasite invasion. The pathogenesis of amoebiasis involves interplay of various molecules secreted by E. histolytica such as LPPG, lectins, cysteine proteases, and amoebapores. Lectins help the parasite attach to the mucosal layer of the host during invasion. The amoebapores destroy the ingested bacteria present in the colonic environment. Cysteine proteases break down the host tissues. Other molecules such as PATMK, myosins, G proteins, C2PK, CaBP3, and EhAK1 play an important role in the process of phagocytosis (the parasite's method of feeding). == Diagnosis ==

With colonoscopy it is possible to detect small ulcers of between 3–5mm, but diagnosis may be difficult as the mucous membrane between these areas can look either healthy or inflamed. Image:Ehistdisp cyst wtmt.jpg|Immature E. histolytica/E. dispar cyst in a concentrated wet mount stained with iodine. This early cyst has only one nucleus and a glycogen mass is visible (brown stain). Image:Amoebic dysentery in colon biopsy (1).jpg|Amoebae in a colon biopsy from a case of amoebic dysentery. File:Immunohistochemical staining of trophozoites (brown) using specific anti–Entamoeba histolytica macrophage migration inhibitory factor antibodies in a patient with amebic colitis.jpg|Immunohistochemical staining of trophozoites (brown) using specific anti–Entamoeba histolytica macrophage migration inhibitory factor antibodies in a patient with amoebic colitis. == Prevention ==

To help prevent the spread of amoebiasis around the home : • Wash hands thoroughly with soap and hot running water for at least 10 seconds after using the toilet or changing a baby's diaper, and before handling food. • Clean bathrooms and toilets often; pay particular attention to toilet seats and taps. • Avoid sharing towels or face washers. To help prevent infection: • Avoid raw vegetables when in endemic areas, as they may have been fertilized using human feces. • Boil water or treat with iodine tablets. • Avoid eating street foods especially in public places where others are sharing sauces in one container Good sanitary practice, as well as responsible sewage disposal or treatment, are necessary for the prevention of E. histolytica infection on an endemic level. E.histolytica cysts are usually resistant to chlorination, therefore sedimentation and filtration of water supplies are necessary to reduce the incidence of infection. == Treatment ==

E. histolytica infections occur in both the intestine and (in people with symptoms) in tissue of the intestine and/or liver. Those with symptoms require treatment with two medications, an amoebicidal tissue-active agent and a luminal cysticidal agent. Individuals that are asymptomatic only need a luminal cysticidal agent. == Prognosis ==

In the majority of cases, amoebas remain in the gastrointestinal tract of the hosts. Severe ulceration of the gastrointestinal mucosal surfaces occurs in less than 16% of cases. In fewer cases, the parasite invades the soft tissues, most commonly the liver. Only rarely are masses formed (amoebomas) that lead to intestinal obstruction (mistaken for caecum and appendicular mass). Other local complications include bloody diarrhea, pericolic and pericaecal abscess. Complications of hepatic amoebiasis includes subdiaphragmatic abscess, perforation of diaphragm to pericardium and pleural cavity, perforation to abdominal cavital (amoebic peritonitis) and perforation of skin (amoebiasis cutis). Pulmonary amoebiasis can occur from liver lesions by spread through the blood or by perforation of pleural cavity and lung. It can cause lung abscess, pulmono pleural fistula, empyema lung and broncho pleural fistula. It can also reach the brain through blood vessels and cause amoebic brain abscess and amoebic meningoencephalitis. Cutaneous amoebiasis can also occur in skin around sites of colostomy wound, perianal region, region overlying visceral lesion and at the site of drainage of liver abscess. Urogenital tract amoebiasis derived from intestinal lesion can cause amoebic vulvovaginitis ''(May's disease)'', rectovesicle fistula and rectovaginal fistula. Entamoeba histolytica infection is associated with malnutrition and stunting of growth in children. == Epidemiology ==

An estimated 500 million people worldwide are infected with Entamoeba, the majority of whom are infected with E. dispar and an estimated 10% are infected with E. histolytica. Mortality from invasive E. histolytica infection is estimated at 100,000 per year. Although usually considered a tropical parasite, the first case reported (in 1875) was actually in St Petersburg in Russia, near the Arctic Circle. Infection is more common in warmer areas, but this is because of both poorer hygiene and the parasitic cysts surviving longer in warm moist conditions. ==History==

Amoebiasis was first described by Fedor A. Lösch in 1875, in northern Russia. The most dramatic incident in the US was the Chicago World's Fair outbreak in 1933, caused by contaminated drinking water. There were more than a thousand cases, with 98 deaths. It has been known since 1897 that at least one non-disease-causing species of Entamoeba existed (Entamoeba coli), but it was first formally recognized by the WHO in 1997 that E. histolytica was two species, despite this having first been proposed in 1925. Between 26 May and 3 September 1998, 177 cases were reported, including 71 cases of intestinal amoebiasis and 106 probable cases of liver abscess. The Nicobarese people have attested to the medicinal properties found in Glochidion calocarpum, a plant common to India, saying that its bark and seed are most effective in curing abdominal disorders associated with amoebiasis. ==Society and culture==

An outbreak of amoebic dysentery occurs in Diana Gabaldon's novel A Breath of Snow and Ashes. == References ==