Filarial Worm (Filariae)
Filarial worm are tissue residing nematodes. Around the world, there
are eight species, which could infected human being.
Species
Location
Wuchereria bancrofti (班氏)
Brugia malayi (马来)
Brugia timori (帝汶布鲁 )
Vector
lymphatic system
lymphatic system
lymphatic system
mosquito
mosquito
mosquito
Onchocerca volvulus (旋盘尾 ) subcutaneous tissue blackfly
Loa loa (罗阿罗阿)
subcutaneous tissue horsefly
Dipetalonema streptocerca (链尾) subcutaneous tissue gnats
Dipetalonema perstans
（常现）
body cavities
Mansonela ozzardi
（奥氏）
body cavities
Wuchereria bancrofti & Brugia malayi
世界性分布，蚊是主要传播媒介
They are the most widely distributed filariae that are transmitted
by mosquitoes.
Morphology
成虫 (adult)
They are elongated, thread-like worms. The adult female worm
of W.bancrofti is larger than B.malayi.
Female produce larvae known as microfilariae.
微丝蚴 (microfilariae)
头隙,体核,尾核
They are elongated and sheathed, with blunt anterior end
and pointed caudal end. A large number of nuclei could
be seen in the body after staining.
班氏微丝蚴与马来微丝蚴的区别
班氏
马来
大小
较大
较小
体态
柔和
僵硬
头隙
呈方形
长方形
体核
圆形，大小一致， 卵圆形，大小不一
尾核
清晰可数
排列密集
无
有
Differential characteristics of microfilariae between
W.bancrofti and B.malayi (1)
W.bancrofti
Length ( m)
Diameter ( m)
Body curves
Cephalic space
Somatic nuclei
Caudal nuclei
200-300
8
regular, smoothly curved
small
well separate
none
B.malayi
220-250
6
irregular twisted
large
over lapped
two
区别的意义
1.致病性不同 班氏大
2.分布不同
班氏分布广
3.药敏性不同 马来对药敏感
 difference in pathogenicity
W.bancrofti more heavy
 difference in distribution
W.bancrofti worldwide distributed
 difference in drug sensitivity
B.malayi is more sensitivity in drug
在蚊体内有腊肠期蚴;丝状蚴,
感染期幼虫为丝状蚴(filariform larva)
microfilariae in the mosquito first into a rhabditiform larva
(Sausage shaped larva) then into an filariform larva------
infectious stage
Life cycle
The life cycle of two species are similar. The larvae develop in the
mosquito which acts as vector, and the adults develop in the human.
adlut
lymphatic
system
microfilariae
sausage shaped larva
filariform larva
peripheral
blood
thoracic musculature
of mosquito
labium of
mosquito
human infected
larva enter the lymphatic system
成虫
(淋巴系统)
微丝蚴
(血液)
腊肠期幼虫
(蚊胸肌)
丝状蚴
(蚊下唇)
蚊
叮
吸
血
在蚊体内的发育, Development in the mosquito:
The microfilariae ingested by the mosquito along with its blood meal
migrate to its muscles.
After 6 to 14 days of development, the larva force their way out of
muscles, migrate to the proboscis (labium).
During the blood meal the developed larva emerge from proboscis
onto the skin of the new host.
# some factors effected the development of larva in mosquito
W.bancrofti:
B.malayi
vector
Culex
淡色库蚊,致倦库蚊
Anopheles, Aedes 中华按蚊,嗜人按蚊,东乡伊蚊
在人体内的发育
Development in the human
On penetrating the skin through the bite wound, the larva pass to the
lymphatic vessels and nodes
After copulation, the female produces microfilariae in about 3 months
infection
The microfilariae migrate from the parent worm the through the walls
of the lymphatics to the neighboring small blood vessels or are carried
in the lymphatic circulation to the bloodstream
Microfilariae appear in the greatest number in the peripheral blood
between 8 pm and 4 am
nocturnal periodicity-------- the microfilariae, present in very
small numbers or often undetectablein the peripheral circulation
during the daytime, then appear in the greatest density at night,
when absent from the peripheral circulation the microfilariae
are found in the capillaries of the lung
夜现周期性(nocturnal periodicity)
微丝蚴白昼滞留于肺血管内，夜晚则出现在外周血液的现象。
Microfilariae of Wuchereria bancrofti
Nocturnal periodicity of microfilariae
Differential characteristics of microfilariae between
W.bancrofti and B.malayi (2)
W.bancrofti
Location
nocturnal
periodicity
reservoir host
B.malayi
deep or near surface
lymphatic system
near surface
lymphatic system
10 pm—2 am
8 pm—4 am
-
+
致病 (Pathogenicity)
丝虫病主要是由成虫引起的
Filarial symptoms are caused mainly by the adult worms,
living as well as dead and degenerating
Microfilariae cause less pathology, although they have been associated
with tropical pulmonary eosinopholia granulomas of the spleen, and
allergic reactions following their destruction by drugs
Clinically, the disease can be divided into incubation, acute,
and chronic phase
Incubation phase: 1. asymptomatic and may last for a year or more
2. may include low-grade fever caused by
lymphatic inflammation
Acute phase:
Chronic phase:
an allergic response to the products of dying and
degenerating adult worms -----lymphangitis, funiculititis, orchitis,
epididymitis filarial fever
repeated lymphangitis granuloma fibrosis
obstruction of lymph vessels lymph varices
rupture of lymphatic proliferation of connective
tissues elephantiasis
elephantiasis
hydrocele testis
W.bancrofti
chyluria
淋巴(结)管炎
液体外溢
增生性肉芽肿
破裂
曲张
1.淋巴液肿
(1)
象皮肿(elephantiasis)
(2)
睾丸鞘膜积液
2.乳糜尿
纤维化(纤维组织增生)
压力↑
管道阻塞
诊断
(一) 病原诊断
1.血检
2.体液和尿液检查微丝蚴
Examination of blood
thick blood film-----detected microfilariae
lysed blood check -----concentrated
Examination of aspiration ( induction)
3.成虫检查
直接或以活检
Detection of adult worm
(二)血清学检查
(三)其他
mAb, ELISA, PCR
流行因素
Epidemiology
(一)分布：
世界性分布
W.bancrofti is worldwide distributed
B.malayi is restricted to Asia
(二)流行环节
1.传染源
Source of infection: patients, infected persons
2.传播媒介 ：蚊是主要传播媒介，主要蚊媒如下：
Transmission: mosquito Culex Anopheles, Aedes
淡色库蚊
嗜人按蚊
班氏丝虫
马来丝虫
中华按蚊
W.bancrofti:
B.malayi
致倦库蚊
东乡伊蚊
3.易感人群
4.影响因素
防治原则
Treatment & Prevention
(一)普查普治
海群生diethylcarbamzine (DEC) hetragan治疗
Diethylcarbamazine(hetrazan) is the first choice in treatment of
filarial worm.
A single-dose treatment of ivermectin plus Diethylcarbamazine
has also proven highly effective, producing a 99 % reduction
in the number of microfilariae
(二)防蚊灭蚊
(三)加强监测
Mass treatment coupled with the use of screens, insect repellents
and insecticides has proven effective in the filarial control
Onchocerca volvulus
Onchocerciasis is considered by WHO the world’s second leading
infectious cause of human blindness
Adult worms are found in fibrous nodules called onchocercomas
in the subcutaneous connective tissues and viscera of humans
Adult worms may cause minor pathological alterations
When microfilariae invade the cornea, cause inflammation of the
sclera, cornea, iris and retina, lead to impaired vision or the total
blindness known as “ river blindness”
The presence of microfilariae in the connective of the skin,
produces severe dermatitis
Worldwide, there are estimated to be 20 million (20000000)
cases of onchocerciasis, approximately 96 % of the cases are in
tropical Africa
Microscopically demonostration of microfilariae in dermal
lymph of skin biopsyis proof of infection, or identification
of adults in skin nodules
Ivemectin, administered in a single dose, the most effective
treatment, Diethylcarbamazine(hetrazan) also, however, the
drug does not affect adult worms------surgical
Loa loa
Loasis is limited to the African
The parasite usually cause no serious damage to the host
Adult worm in subcutaeous tissue, in eye, Calabar swelling
Microfilariae can be seen in unstained fresh prepared blood
Diethylcarbamazine(hetrazan) is the first choice in treatment of
filarial worm.
Trichinella spiralis
旋毛虫(Trichinella spiralis)成虫寄生在小肠下部的肠壁，
幼虫寄生在人体横纹肌中，引起旋毛虫病(Trichinellosis)，
为人兽共患病。
食源性寄生虫病，特点：地区性、群体性、食源性、季节性
Trichinellosis is the disease among human and animal, a zoonosis.
The infection is endemic in many areas of the world where raw or
undercooked meat, mainly pork is consumed.
形态 Morphology
成虫 Adult
small & slender male:
female:
1.5 mm X 0.04 mm
3.5 mm X 0.06 mm
deposited larva
幼虫 Larva
enveloped, 0.25-0.5 mm X 0.21-0.42 mm
生活史
Life cycle
成虫和幼虫均寄生在同一宿主体内
完成生活史需更换宿主
Human infection results from consumption of meat,
most communly poorly cooked pork, containing
encapsulated larva.
Life Cycle of Trichinella spiralis
成虫 交配 幼虫
4-6d
肠淋巴管或静脉
心
肺
全身各处
幼虫
(囊包)
食
入
脱
囊
2-3days
幼虫
4-6 days
Adult
lymphatic vessels heart lung
Larva
spread
Larva
another
2-3 days
Larva
Larvae can survive only in the skeltal muscle & become encysted in
2 to 3 weeks
致病 Pathogenicity
Trichinellosis, mainly result from larval invasio of muscle & other
tissues and the hperimmune reaction of the host to the metabolic
by-products and secretions of the larvae
1.侵入期 肠道症状
Invasion stage: due to penetration of adult female & larva into the
mucosa & submucosa, begins 24 hrsafter infection and lasts for 1
to 7 days
asymptomatic or transient gastrointestipational
complaints
2.幼虫移行期 全身症状、肌肉症状等一系列严重症状
Migration stage: begins about 1 week after infection and lasts
after female worm die(4-6 wks)
triad of myalgia palpebral edema eosinophilia fever
3.成囊期
Encystment stage:
诊断
病原诊断
Laboratory diagnosis
组织活检
免疫诊断
皮内试验、环蚴沉淀试验、皂土絮状试验、ELISA。
最近也将检测急性期的循环抗原作为手段之一。
•A parasitologic diagnosis is made by means of biopsy or at autopsy
•Serologic tests
EIA dot immunobinding to detect circulating
parasitic antigen
流行和防治
Epidemiology, treatment, prevention
主要预防措施：不食生肉
mebendazole对成、幼虫均有效
This infection is much less common in Africa and Asia than in
Europe and America.
The drug of choice is Mebendazole, which can kill both the larva
and adult worms. ( albendazole is also effective)
No raw or undercooked meat