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. This 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.
（林建银）
