锥虫
Trypanosome
According to the geographic distribution & characteristic
pathogenicity, members of trypanosomes that infect humans
can be divided into two major groups. One group are African
trypanosomes, which include Trypanosoma rhodesiense
and Trypanosoma gambiense, the other group is American
trypanosome namely Trypanosoma cruzi
非洲锥虫病——非洲睡眠病 (African sleeping sickness)
由布氏冈比亚锥虫和布氏罗得西亚锥虫引起，由舌蝇传播。
Morphology & life cycle
Tow distinct forms------the trypomastigote------the shape of the
letters C or U in stained blood films, in the bloodstream, the
trypomastigotes exhibit three forms (1) slender form—long,
an undulating member, a free flagellum (2) stumpy form—short,
lacking flagellum(3) a form intermediate between both
------the epimastigote----with a large nucleus,
a kinetoplast, an undulating
member, a free flagellum
舌蝇
粗短型锥鞭毛体
舌蝇
上鞭毛体
循环后期锥鞭毛体
中间型鞭毛体
细长型鞭毛体
Human beings become infected with Trypanosoma rhodesiense
or T.gambiense follwing the infection of metacyclic
trypomastigotes by the tsetse fly during the blood meal
Once introduced into the bloodstream, trypomastigotes spread &
multiply rapidly, migrate to the cerebrospinal fluid
Tsetse fly get infected when it ingested stumpy trypomastigotes
during its blood meal
The stumpy trypomastigotes elongate, multiply, converting
into epimastigote, then transform into metacyclic
trypomastigotes, which are infective stage for human beings
Pathogenicity
Early stage (初发反应期): inflammatory reaction called
trypanoosomal chancer occurs at the site of the bite—reddening
in the skin, a swelling 1—5 cm in diameter, enlargement of
adjacent lymph nodes
Hemolymphatic stage (血淋巴期): the blood & lymph are invaded,
headache, irregular fever develop, enlargement of lymph nodes
—in the neck & supraclavicular area
Winterbottom’s sign
Central nervous system stage (脑膜脑炎期): final stage of disease
mental retardation, tremors, meningoencephalitis
the patient slips into coma and death
Epidemiology
T. gambiense is found in tropical West Africa & Central Africa
T. rhodesiense is found in East & Central Africa
主要由舌蝇传播
移植、输血、注射事故也可传播
Blood transfusion, transplant are additional routes of
transmission
The antelope (羚羊) may serve as reservoir host
保虫宿主羚羊
Diagnosis
Multistep procedure:
clinical assessment—
examination of blood smears
—bone marrow, or CSF for
trypomastigotes
antibody detection—IFA.ELISA
PCR
Treatment
Suramin 早期疗效100%
Eflornithine（依弗鸟氨酸）早晚期会更有效
Suramin is effective against African sleeping sickness when
treatment is initiated early in the course of the disease,
Eflornithine will be more effective one
Trypanosoma cruzi
由 Trypanosoma cruzi引起美洲锥虫病 —
Chagas’ disease,
Trypanosoma cruzi is responsible for Chagas’disease
由锥蝽 (reduviid bug vector)传播。
Morphology & life cycle
amastigote: a nucleus, a kinetoplast, a blepharoplast, an axoneme
trypomastigote: similar to that of African trypanosomes
T. cruzi is most frequently transferred to a
human host when a reduviid bug vector
(锥蝽)defecates infective metacyclic
trypomastigotes near the site of its
blood meal
After entry into host, trypomastigotes invade surrounding cell &
transform into amastigotes, which are multiply, destroy the host
cells, convert back into trypomastigotes
The resulting trypomastigotes migrate into the blood, and penetrate
additional cells in the body, transform back into amastigotes, the
replication & destruction cycle repeat------heart muscle, liver &
brain will become infected
The trypomastigotes are transmitted back to the reduviid bug via
a blood meal
锥蝽
吸血
锥鞭毛体
无鞭毛体
上鞭毛体
球鞭毛体
上鞭毛体
无鞭毛体
循环后期锥鞭毛体
锥蝽
粪便污染
The matacyclic trypomastigotes are then passed with the feces
when the bug defecates near the site of its next blood meal,
the cycle begins again
夜間吸血
糞便中虫体经傷口侵入
先天感染
輸血
Pathogenicity
the parasite invade macrophage of the subcutaneous tissue at the
site of infection, causing a local, edematous swelling called a
chagoma, kiss bugs ( about 1-3 weeks after infection, fever,
headaches, malaise, and prostration may develop)
急性期Chagoma、kiss bugs伴发热、头痛等，也可肝脾肿大
In chronic stage: myocarditis, enlargement of colon and esophagus,
hepatosplenomegaly
慢性期 急性后10-20y，心肌炎、巨食道、巨结肠
Epidemiology
T.cruci is found in South and Central America,
rarely in North America
主要经锥蝽传播 移植、输血、胎盘或被锥蝽粪便污染的
食物也可传播，保虫宿主犰狳。
The highest prevalence of disease
is in Brazil
Additional routes of T.cruci transmission include blood transfusion,
sexual intercourse, transplacental, and entry through the mucous
membranes when the bug bite occurs near the eye or month
Reservoir host--Armadillo (犰狳)
Diagnosis
Giemsa-stained blood slides
lymph node biopsy giemsa-stained slides
culture of blood—NNN medium—amastigotes
serologic tests—IFA, ELISA
xenodiagnosis
PCR
Treatment
The treatment of choice for infection with T.cruci is nifurtimox