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Amoebiasis, also known as amebiasis or entamoebiasis, is an infection caused by any of the amoebas of the ''Entamoeba'' group. Symptoms are most common upon infection by ''Entamoeba histolytica''. Amoebiasis can present with no, mild, or severe symptoms. Symptoms may include abdominal pain, mild diarrhoea, bloody diarrhea or severe colitis with tissue death and perforation. This last complication may cause peritonitis. People affected may develop anemia due to loss of blood.〔 Invasion of the intestinal lining causes amoebic bloody diarrhea or amoebic colitis. If the parasite reaches the bloodstream it can spread through the body, most frequently ending up in the liver where it causes amoebic liver abscesses. Liver abscesses can occur without previous diarrhea. Cysts of ''Entamoeba'' can survive for up to a month in soil or for up to 45 minutes under fingernails. It is important to differentiate between amoebiasis and bacterial colitis. The preferred diagnostic method it through faecal examination under microscope, but requires a skilled microscopist and may not be reliable when excluding infection. Increased white blood cell count is present in severe cases, but not in mild ones. The most accurate test is for antibodies in the blood, but it may remain positive following treatment.〔 Prevention of amoebiasis is by separating food and water from faeces and by proper sanitation measures. There is no vaccine. There are two treatment options depending on the location of the infection. Amoebiasis in tissues is treated with either metronidazole, tinidazole, nitazoxanide, dehydroemetine or chloroquine, while luminal infection is treated with diloxanide furoate or iodoquinoline. For treatment to be effective against all stages of the amoeba may require a combination of medications. Infections without symptoms do not require treatment but infected individuals can spread the parasite to others and treatment can be considered. Treatment of other ''entamoeba'' infections apart from ''E. histolytica'' is not needed.〔 Amoebiasis is present all over the world. About 480 million people are infected with ''E. histiolytica'' and this results in the death of between 40,000–110,000 people every year. ''E. dispar'' is more common in certain areas and symptomatic cases may be fewer than previously reported. The first case of amoebiasis was documented in 1875 and in 1891 ''E. histiolytica'' was identified resulting in the terms ''amoebic dysentery'' and ''amoebic liver abscess''. Further evidence from the Philippines in 1913 found that upon ingesting cysts of ''E. histiolytica'' volunteers developed the disease. It has been known since 1903 that at least one species of non-disease causing entamoeba exist, but it was first formally recognized by the WHO in 1997. In addition to the recognized ''E. dispar'' evidence shows there is likely another species of ''E. moshkovskii'' as well. The reason these species haven't been differentiated until recently may be because they look very similar. == Signs and symptoms == Most infected people, about 90%, are asymptomatic, but this disease has the potential to make the sufferer dangerously ill. It is estimated that about 40,000 to 100,000 people worldwide die annually due to amoebiasis.〔Atlas of Human Infectious Diseases, First Edition. Heiman F.L. Wertheim, Peter Horby and John P. Woodall., 2012, Blackwell Publishing Ltd.〕 Infections can sometimes last for years. Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks. Symptoms can range from mild diarrhea to severe dysentery with blood and mucus. The blood comes from lesions formed by the amoebae invading the lining of the large intestine. In about 10% of invasive cases the amoebae enter the bloodstream and may travel to other organs in the body. Most commonly this means the liver,〔 as this is where blood from the intestine reaches first, but they can end up almost anywhere in the body. Onset time is highly variable and the average asymptomatic infection persists for over a year. It is theorized that the absence of symptoms or their intensity may vary with such factors as strain of amoeba, immune response of the host, and perhaps associated bacteria and viruses. In asymptomatic infections the amoeba lives by eating and digesting bacteria and food particles in the gut, a part of the gastrointestinal tract. It does not usually come in contact with the intestine itself due to the protective layer of mucus that lines the gut. Disease occurs when amoeba comes in contact with the cells lining the intestine. It then secretes the same substances it uses to digest bacteria, which include enzymes that destroy cell membranes and proteins. This process can lead to penetration and digestion of human tissues, resulting first in flask-shaped ulcers in the intestine. ''Entamoeba histolytica'' ingests the destroyed cells by phagocytosis and is often seen with red blood cells (a process known as erythrophagocytosis) inside when viewed in stool samples. Especially in Latin America, a granulomatous mass (known as an amoeboma) may form in the wall of the ascending colon or rectum due to long-lasting immunological cellular response, and is sometimes confused with cancer. "Theoretically, the ingestion of one viable cyst can cause an infection." 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「amoebiasis」の詳細全文を読む スポンサード リンク
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