第五节 其他毛滴虫
一、人毛滴虫
人毛滴虫（Trichomonas hominis Daraine 1860)寄生于人体盲肠和结肠，其生活史仅有滋养体阶段，无包囊。滋养体呈梨形，形似阴道毛滴虫，具有3～5根前鞭毛和1根后鞭毛。后鞭毛与波动膜外缘相连，游离于尾端。波动膜的内侧借助一弯曲、薄杆状的肋与虫体相连。肋与波动膜等长，染色后的肋是重要的诊断依据。活虫体可做急速而无方向的运动。波动膜在运动中起旋转作用，而前鞭毛起推动作用。胞核单个，位于前端，核内染色质分布不均匀。胞质内含有食物泡和细菌。一根纤细的轴柱由前向后贯穿整个虫体（图10-7 )。
虫体以纵二分裂法繁殖。滋养体在外界有较强的抵抗力，为感染阶段。目前尚无证据表明人毛滴虫对人体有致病作用。有报道认为本虫可导致腹泻，调查表明，人毛滴虫在腹泻患者中的检出率是健康人的几倍甚至十多倍，但有人认为腹泻与本虫感染相伴，并非本虫所致。
可采用粪便直接涂片法镜检滋养体或用人工培养基（Boeck和Drobhlav二氏培养基)分离虫体。
本虫呈世界性分布，以热带和亚热带较为常见。感染率各地不同，我国为0.2%～9.4％，以儿童较为常见。本虫感染途径为粪—口传播。误食被滋养体污染的饮水和食物均可感染。治疗首选药物为甲硝咪唑（灭滴灵)，中药雷丸疗效也较好。
二、口腔毛滴虫
口腔毛滴虫（Trichomonas tenax Muller, 1773)寄生于人体口腔，定居于齿龈脓溢袋和扁桃体隐窝内，常与齿槽化脓同时存在。生活史仅有滋养体阶段，外形似阴道毛滴虫，呈梨状，有4根前鞭毛和1根无游离端的后鞭毛，波动膜稍长于阴道毛滴虫，核单个，位于虫体前部中央，含丰富染色质粒，轴柱较纤细，沿虫体末端伸出（图10-8)，以纵二分裂法繁殖。
本虫是否致病尚无定论。有学者认为口腔毛滴虫为口腔共栖性原虫，但另有学者认为与牙周炎、牙龈炎、龋齿等口腔疾患有关。曾有呼吸道感染及扁桃体隐窝内查见本虫的报道。实验诊断可用牙龈刮拭物作生理盐水涂片镜检或作培养。滋养体在外界有较强抵抗力，室温下可存活3～6天。接吻是本虫的直接传播方式；也可通过飞沫、食物、餐具等传播。平时注意口腔卫生是预防本虫感染的最有效方法。
Summary This chapter discusses human protozoan parasites belonging to several different genera—Leishmania and Trypanosoma; Giardia and Trichomonas as well as the diseases caused by these protozoa.
Numerous species of Leishmania cause forms of leishmaniasis in various geographic areas, including visceral leishmaniasis (L. donovani), mucocutaneousal leishmaniasis (L. braziliensis) and cutaneous leishmniasis (both L. tropica and L. mexicana). Leishmania occurs as an intracellular amastigote in the mammalian host and as promastigote in the intestine of the sand flies, which act as vectors. The severity of disease depends on the infecting species and on the host’s immune response.
Trypanosoma is the pathogen of Trypanosomiasis, in which T. brucei causes African trypanosomiasis (Sleeping Sickness) and T. cruzi causes American trypanosomiasis (Chagas’ disease).
Giardiasis, caused by Giardia lamblia, may be asymptomatic or may cause a variety of intestinal symptoms, including chronic diarrhea, steatorrhea, cramps, bloating, and fatigue and weight loss. There is evidence that some animal Giardia strains may infect humans.
Trichomonas vaginalis is the pathogen of trichomoniasis, which is a common urogenital disease in women. Vaginitis, with foul-smelling discharge and small hemorrhagic lesions, may be present; frequency of urination and painful urination are common symptoms.
Another trichomonad parasite inhabits the intestinal tract in the area of the cecum. Th医.学全在线www.med126.comis parasite is called either T. hominis or, because most of these organisms in culture have five anterior flagella, Pentatrichomonas hominis. Trichomonad tenax inhabits the human oral cavity, occurring particularly in tartar, cavities, and at the gingival margins. Although considered nonpathogenic, it has been reported, rarely, in lung or thoracic abscesses.
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