Review of intestinal helminths
Ascaris lumbricoides (roundworm)
似蚓蛔线虫（蛔虫）
Trichuris trichiura (whipworm)
毛首鞭形线虫 （鞭虫）
Enterobius vermicularis (pinworm)
蠕形住肠线虫（蛲虫）
Ancylostoma duodenale
Necator americanus
(hookworms) 钩虫
Tissue-blood dwelling nematodes
Trichinella spiralis
旋毛形线虫
Wuchereria bancrofti 班氏吴策线虫
Onchocerca volvulus 旋盘尾丝虫
--Filaria 丝虫
The history of Trichinella spiralis
In year 1835，Young Jim Paget, a first year medical student at
London Hospital Medical School, rushed into the autopsy room.
The 51 yr-old Italian bricklayer who had died of tuberculosis, and
that they were now dissecting, also had "sandy diaphragm," a
condition that dulled even the sharpest of scalpels. Well, anyway,
when they had all cleared the room, Jim quietly stole back in and
removed a small bit of muscle tissue from the diaphragm. He was
more than curious as to the nature of "sandy diaphragm". He first
examined it with his trusty hand lens he carried for just such a
situation. He thought he saw small worms coiled up inside
each nodule. Upon even higher magnification, the presence of
coiled worms was revealed.
(From www.trichinella.org)
Trichinella spiralis
Jim Paget
Worms in the “sandy diaphragm”
Trichinella spiralis
Trichina worms were observed in
pork in 1846 by Joseph Leidy. He
saved hundreds of lives by
recommending cooking pork at a
high enough temperature to kill the
organism.
Life cycle work out in1850’s
By Rudolph Virchow.
Trichinella control
Rudolf Virchow (Germany)
suggested mandatory
diagnosis of all meat at the
slaughterhouses in 1877
This has greatly reduced
trichinellosis as human health
Problem.
Trichinella spiralis
- cause 旋毛虫病
trichinosis, trichiniasis, or trichinelliasis
Worldwide Distribution
Parasitic zoonosis
Food borne parasitosis
Distribution of Trichinella spiralis
Trichinosis is most common in temperate and arctic
climates - high prevalence in pork-eating areas of
the world.
arctic
temperate
Adults of Trichinella spiralis
Adults : small, 1.5~4 mm
Larva: females give birth to larva
( Eggs: hatch in uterus 子宫)
特点：直接产幼虫
stichosome
成虫形态在诊断
上无意义！
杆状体
Hatched Larva
Encysted larva 幼虫囊包-- infective stage
0.25~0.5mm × 0.21~0.42mm
Lemon shape
1~2 larva in the cyst
Life
cycle
Adult female in mucosa of
small intestine
Trichina cysts in skeletal
muscle骨骼肌
Pathogenisis
3 stages ：
1. Invasion – 1 week
first symptoms appear 12 hours to 2
days following ingestion of trichina cysts
Nausea, vomiting, diarrhea, abdominal pain,
headache with slight fever
2. migration of larvae – 2 week to 2 months
penetration and encystment
in skeletal muscles 骨骼肌
2. migration of larvae – 2 week to 2 months
Weakness， Headache and dizziness 头昏，
Fever,chills and sweating, Myalgia 肌痛
perorbital edema
splinter hemorrhages
（under finger nails）
Eosinophilia 嗜酸性细胞增多
Deaths are rare and due to myocarditis 心肌炎,
encephalitis 脑炎 and pneumonia肺炎
3.calcification (if one survives stage2!)
- occurs several months after infection
- calcium is deposited around the cysts
- Larva eventually die in a year or longer
In human infections,
5 larvae/gram body weight are fatal.
Diagnosis
1. Muscle biopsy : trichina cysts
can be seen with microscope
Muscle samples were squeezed
between two glass plates
肌肉压片
2. ELISA to identify Trichinella antibodies
Others？:
Epidemiology
1. Cosmopolitan distribution
2. Source of infection is pork or pork products
infection is most frequents among ethnic groups
disposed to eat raw or poorly cooked pork
products
Treatment of Trichinella spiralis
Drugs:
Mebendazole（甲苯哒唑）
Albendazole（阿苯哒唑,丙硫咪唑）
Others:
Prevention of Trichinella spiralis
1. Thorough cooking
(temperature above 58o C)
microwave cooking of pork roasts and chops (with bone) is
NOT effective in killing trichina
2. freezing for 20 days will kill temperate climate strain
- freezing is NOT effective against the arctic strain
- smoking, salting, and drying pork, bear or other meat will NOT
kill trichina larvae
Prevention of Trichinella spiralis
3. - Do not feed pork scraps in garbage to pigs
- eliminate rats in areas where pigs are kept
Tissue-blood dwelling nemotodes
Filaria
-cause filariasis
Four important filarial worms parasitic in humans are:
Wuchereria bancrofti 班氏吴策线虫
Onchocerca volvulus 旋盘尾丝虫
Brugia malayi 马来布鲁线虫
Loa loa 罗阿罗阿线虫
W. bancrofti is strictly a human pathogen and is
distributed in tropical areas worldwide
More than 80 million were affected
Orient, South Pacific, and Southern Asia to India – overlaps
with Wuchereria bancrofti - but does not occur in Africa or
South America
B. malayi infects a number of wild and domestic animals
Morphology--Adults of Wuchereria bancrofti
Adults occur in the lymphatic vessels
（Adult B. malayi are only half the size of W. bancrofti ）
filariform larva 丝状蚴
Microfilariae of Wuchereria bancrofti
Microfilariae are seen in blood smears and are DIAGNOSTIC
worms are 230-320 µm long
Morphological differences of microfilariae
of Wuchereria bancrofti and Brugia malayi
Wuchereria bancrofti
Length
(µm)
Appearance
体态
244-296× 5.3-5.7
graceful sweeping
curves
Cephalic space length equals width
头隙
Body nuclei well defined, discrete,
体核
round, uniform sized
Tail
尾核
no terminal nuclei
Brugia malayi
177-230× 5 -6
Irregular kinky
curves
length twice width
blurred, intermingled
nuclei crowded together
two terminal nuclei
Filariform larve-infective stage
Microfilariae of Wuchereria bancrofti
Nocturnal periodicity of microfilariae 夜现周期性
Pathology of Wuchereria bancrofti
Incubation period
no symptoms
3 clinical phases:
1. microfilaremia - no symptoms or mild symptoms
微丝蚴血症
Acute allergic inflammatory phase
a. lymphadenitis, lymphangitis
淋巴结炎
淋巴管炎
Acute allergic inflammatory phase
b. filarial fever 丝虫热
c. funiculitis, orchitis, epididymitis
精索炎， 睾丸炎，附睾炎
3. chronic Obstructive phase
a. Elephantiasis 象皮肿
The disfigured legs of lymphatic filariasis
patients waiting for medical attention
b. chyluria 乳糜尿
c. hydrocele testis 鞘膜积液
Brugia malayi 马来丝虫
Adults live in lymphatic vessels and cause elephantiasis in
arm and leg.
Difference between W.r and B.m? —— discuss later
Diagnosis
Identifying microfilaria in blood or other fluid
direct blood films
concentrations of blood specimens and urine
specimens
Identifying adults
Serologic testing
Epidemilogy
1. World Wide distribution
2. Source of infection: patients and infected patients
3. Transmission: by mosquitto
Brugia malayi
Wuchereria bancrofti
Treatment of Wuchereria bancrofti
Drugs : hetrazan 海群生
are somewhat effective
kill microfilariae and adults with careful administration
Global Programme to Eliminate Lymphatic Filariasis
6 mg/kg diethylcarbamazine citrate
(DEC) + 400 mg albendazole;
150 µg/kg ivermectin + 400 mg
albendazole (in the case of coendemicity with onchocerciasis)
A third option is to follow a treatment
regimen using DEC-fortified cooking
salt daily for a period of 12 months.
Drug
Year of
registration
Indication
Praziquantel
1980
Schistosomiasis
Mefloquine
1984
Malaria
Ivermectin
1987
Onchocerciasis
Halofantrine
1988
Malaria
Eflornithine
1991
African Tryp.
Liposomal
amphotericin B
1994
Leishmaniasis
(Kala azar)
Partners
Bayer
Hoffman La
Roche,
WRAIR
Merck
Smith Kline
Beecham, WRAIR
Marion Merrel
Dow
NeXstar
Artemether
1997
Malaria
Rhone Poulenc
Rorer, Kunming
Artemetherumefantrine
1999
Malaria
Novartis
Artemotil
(beta-arteether)
2000
Malaria
Artecef, WRAIR,
Dutch Min. Dev.
Miltefosine
2002
Leishmaniasis
(Kala azar)
Chlorproguanildapsone
2003
Malaria
Zentaris,
Indian CMR
Glaxo Smith Kline,
DFID
others:
Pressure bandages on enlarged limbs forces lymph out.
弹力绷带捆绑
Surgery can be used to remove elephantoid tissue if muscle
involvement is minimal.
外科手术
Onchocerca volvulus 旋盘尾丝虫
Causative agent of onchocerciasis （river blindness）
90 million, 17.6 million, 326 thousand
Adults of Onchocerca volvulus
Skin nodule
Microscopic section showing adults
and scar tissue reaction
Microfilariae of Onchocerca volvulus
Unsheathed microfilariae occur in the skin, never the
bloodsteam
Simulium 蚋
Pathogenisis of adults
Nodules (about ½ -1 inch in
diameter) are most common in
Africa
Nodules in Central & South
America.
Nodules are relatively benign
Pathogenisis of Microfilariae
Microfilariae in the skin
- itching is so severe some people
have committed suicide
Microfilariae in skin
- in parts of Africa, the skin of the scrotum 阴囊 and
inguinal area 腹股沟 loses its elasticity
2. Microfilariae invade the eye
(occur as microfilariae die in the
eye)
Microfilariae invade the eye
In many parts of Africa, the sighted young are responsible for
leading the older blind adults.
Diagnosis of Onchocerca volvulus
Examination of microfilariae or adult in skin nodule, eye etc.
TREATMENT of Onchocerca volvulus
1. Drugs
Ivermectin （150mg/kg )
Every 6-12month
2. excise of skin nodule etc
Onchocerca volvulus
PREVENTION –
blackflies control
Loa
loa
Vector : chrysops 斑虻
about 2 million
“眼虫”
adults
occasionally migrate through
the eye
Calabar swelling 卡拉巴丝虫性肿 块
Microfilariaes present during the daytime
Pathogenesis of Loa loa
Adults cause Calabar swellings.
Eye swells when worms migrate through.
Diagnosis and control of Loa Loa
Diagnosis：
Control： drugs are not so effective for adults
surgical removal of worms
讨论课要求
1. 以2~3人组成小组，以小组为单位计分，要求小组成
员分工合作完成
2. 每组同学自由讲解时间控制在12分钟，留3分钟提问
和讨论
3. 每位同学必须至少参加一次讨论
4. 每位同学还必须完成一次课后作业（另行布置）
5. 班长负责协调统计
人体寄生虫学讨论课
讨论主题：总论、线虫
1. 人群土源性线虫的感染率是衡量一个国家或地区整
体发展水平和文明程度的重要指标，如果你是某农
村疾控中心的人员，你在控制土源性线虫感染方面
有哪些具体的措施？
2. 淋巴丝虫病是WHO要求全球范围内限期消除的寄生
虫病，请从生物学及社会学等因素分析人类提出
该目标的依据及具体的措施？
3.
当前哪些因素导致新现和再现寄生虫病的上升，
请举例说明。
补充：
1.
人体寄生虫学研究发展史。
2.
人类能最终消灭人体寄生虫病吗，谈谈你的观点。
3.
寄生虫对人类社会的贡献。
4.
各国（地区）人体寄生虫流行及防治介绍