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Tularemia (or tularaemia; also known as Pahvant Valley plague,〔 rabbit fever, deer fly fever, and Ohara's fever) is a serious infectious disease caused by the intracellular bacterium ''Francisella tularensis''. A Gram-negative, nonmotile, pleomorphic coccobacillus, the bacterium has several subspecies with varying degrees of virulence. The most important of those is ''F. tularensis tularensis'' (Type A), which is found in lagomorphs (rabbits, hares and pikas) in North America, and it is highly virulent in humans and domestic rabbits. ''F. tularensis palaearctica'' (Type B) occurs mainly in aquatic rodents (beavers, muskrats) in North America and in hares and small rodents in northern Eurasia. It is less virulent for humans and rabbits. The primary vectors are ticks and deer flies, but the disease can also be spread through other arthropods.〔 The disease is named after Tulare County, California. ==Signs and symptoms== Depending on the site of infection, tularemia has six characteristic clinical variants: ulceroglandular (the most common type representing 75% of all forms), glandular, oropharyngeal, pneumonic, oculoglandular, and typhoidal. The incubation period for tularemia is one to 14 days; most human infections become apparent after three to five days. In most susceptible mammals, the clinical signs include fever, lethargy, loss of appetite, signs of sepsis, and possibly death. Nonhuman mammals rarely develop the skin lesions seen in people. Subclinical infections are common, and animals often develop specific antibodies to the organism. Fever is moderate or very high, and tularemia bacilli can be isolated from blood cultures at this stage. The face and eyes redden and become inflamed. Inflammation spreads to the lymph nodes, which enlarge and may suppurate (mimicking bubonic plague). Lymph node involvement is accompanied by a high fever. Death occurs in less than 1% of cases if therapy is initiated promptly. The bacteria can penetrate into the body through damaged skin and mucous membranes, or through inhalation. Humans are most often infected by tick bite or through handling an infected animal. Ingesting infected water, soil, or food can also cause infection. Tularemia can also be acquired by inhalation; hunters are at a higher risk for this disease because of the potential of inhaling the bacteria during the skinning process. It has been contracted from inhaling particles from an infected rabbit ground up in a lawnmower (see below). Tularemia is not spread directly from person to person.〔("WHO Guidelines on Tularemia" ) Published 2007〕 ''Francisella tularensis'' is an intracellular bacterium, meaning it is able to live as a parasite within host cells. It primarily infects macrophages, a type of white blood cell, thus is able to evade the immune system. The course of disease involves the spread of the organism to multiple organ systems, including the lungs, liver, spleen, and lymphatic system. The course of disease is different depending on the route of exposure. Mortality in untreated (before the antibiotic era) patients has been as high as 50% in the pneumoniac and typhoidal forms of the disease, which however account for less than 10% of cases. Overall mortality was 7% for untreated cases, and the disease responds well to antibiotics, with a fatality rate of about 1%. The exact cause of death is unclear, but it is thought to be a combination of multiple organ system failures. 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「tularemia」の詳細全文を読む スポンサード リンク
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