Transcript Morphology－ Adults of

Introduction to the Helminths 蠕虫
Helminths means worms, multicellular organisms.
Phylum
Nemathelminthes
(round worm)
线形动物门
Platyhelminthes
(flatworms)
扁形动物门
Class
Nematoda
线虫纲
Tremetoda
吸虫纲
Cestoda
绦虫纲
The Nematodes 线虫
There are many, many nematodes
2002年诺贝尔奖：程序性细胞死亡
2006 诺贝尔奖: ＲＮＡ干扰机制
C.Elegans
Morphology
Cylindrical, non-segmented, bilaterally
symmetrical and sexes separate
Pseudocele 原体腔
( pseudocoelom)
The body wall:
cuticle 角皮层
hypodermis 皮下层
longitudinal muscle 肌层
The arrangement of the somatic muscles
Polymyarian type
( Ascarids)
Meromyarian type
(Hookworm)
Holomyarian type
( Whipworm)
Digestive system
咽管
Mouth
pharynx
intestine
肠管
anus
肛门
食管
esophagus
Reproductive system
male reproductive system
Testis
睾丸
seminal vesicle
储精囊
vas deferens
输精管
ejaculatory duct
射精管
Most females usually have
two ovaries ，oviducts
and uterus..
ovary—oviduct —uterus.
ovary—oviduct —uterus..
卵巢
输卵管 子宫
vulva -vagina
阴门 阴道
nervous system
Consist of :
circumesophageal nerve ring
咽管神经环
and
2 or 4 longitudinal nerve trunks
神经干
Excretory system
Excretory pore is anterior.
排泄孔
No flame cells are present.
life cycle
M1
Egg
L1
M2
L2
L3
larva
M3
M4
L4
Adult
(male & female)
Kinds of life cycle in nematodes
Direct life cycle:
Intermediate host is not necessary
Ascaris lumbricoides
Trichuris trichiura
Enterobius vermicularis
Hookworms
土源性线虫
（肠道线虫）
Indirect life cycle:
intermediate host is necessary
Trichinella spiralis
Filaria
生物源性线虫
Pathogenesis
1)Larvae：
( 1) dermatitis caused by cutaneous invasion and
subcutaneous migration of larva;
( 2) injury to organs or tissues by migration of larvae in
the body
2) Adults：
(1) injury to intestinal mucosa caused by the parasites
living in gastro- intestinal system
(2) injury to lymphatic system, muscles or nervous system
caused by the parasites living in tissues
What about Egg？
INTESTINAL HELMINTHS
Ascaris lumbricoides (roundworm)
Trichuris trichiura (whipworm)
Enterobius vermicularis (pinworm)
似蚓蛔线虫
毛首鞭形线虫
蠕形住肠线虫
Ancylostoma duodenale and Necator americanus
(hookworms)
钩虫
2004年第二次寄调
Ascaris lumbricoides
(ascarids)
Adults live in intestine of human, cause Ascariasis (蛔虫病)；
Human is the only definitive host of this parasite.
>1
billion world wide
the infective rate
in China 12.72%
Hookworms
Five species of hookworms:
Ancylostma duodenale 十二指肠钩口线虫
Necator americanus
Ancylostma ceylanicum
Ancylostma caninum
Ancylostma brazilience
美洲板口线虫
锡兰钩口线虫
犬钩口线虫
巴西钩口线虫
Adult live in the intestine and take blood from the
host, cause hookworm disease.
国内： 6.12%
Number of humans infected is estimated at 1.2 billion with
50,000 to 60,000 deaths each year.
Enterobius vermicularis
(Pinworm)
Almost anybody can
become infected with
this parasite，
especially children.
国内：10.28%
The worldwide infection
is about 210 million
Morphology
Morphology－ Adult of Ascaris lumbricoides
the largest nematode parasites of humans
Creamy white or pinkish in color
elongate and cylindrical
Morphology－ Adults of Ascaris lumbricoides
Female: measuring 35cm
long, posterior end is
straight
Male: measuring 25cm
long， posterior end is
curved .
Morphology－ Adults of Ascaris lumbricoides
Three lips around
the mouth in
“品”type and
possess small teeth
Morphology－ Adults of Trichuris trichiura
50 mm long
with a slender anterior and a thicker posterior end
The male is smaller and has a coiled posterior end
Morphology－ Adults of Enterobius vermicularis
Adults: pin-like, white, small worm
咽管球
头翼
Female showing esophageal bulb & cephalic alae
Male with curved posterior end, Female has a long pointed end.
Morphology－ Adults of hookworms
Adult:
Slender, pinkish or
creamy-gray in color,
about 10mm in length.
Morphology－ Adults of hookworms
Females:
9-13 mm long
with egg-filled uterus
Males:
7-11 mm long, Posterior
end forms a Copulatory
bursa (交合伞)
Morphology of Ancylostoma duodenale
Buccal capsule contains 2 pairs of large ventral
(anterior) teeth
Copulatory bursa is at posterior end and contains 2
thin spicules that separate distally.
口囊
交合伞
Morphology of Necator americanus
Buccal capsule contains a pair of ventral and dorsal
cutting plates.
Copulatory bursa contains spicules that are fused
distally.
Difference between A.duodenale and N. americanus
A.duodenale
“c”, 1cm±
shape
buccal capsule
“s”, 1cm±
flat and oval-shape
oval-shape
two pairs
one pair cutting plates
Copulatory bursa
spicule
N. americanus
round
two, separated
oblate
two, fused at
their ends
Morphology－ larva of hookworms
rhabditiform Larva 杆状蚴
filariform larva : infective stage
Morphology－ Eggs of Ascaris lumbricoides
Eggs are unembryonated when passed in the feces.
Embryonation occurs in the soil.
broadly oval
yellowish to
brown in color
Thick shell
protein coat
ovum
Unembryonated egg in feces
fertilized
unfertilized and fertilized egg
Morphology－ Eggs of Ascaris lumbricoides
Embryonated egg in soil
Decorticated egg
(lost outer albuminous
coating)
Morphology－ Eggs of Trichuris trichiura
size: 50-54 µm by 22-23 µm,
smaller than Ascarids’
Shape：a typical barrel
Color：yellow-brown
unstained two polar plugs
Shell： quite thick
Contains： unembryonated
egg
Morphology－ Eggs of Enterobius vermicularis
size:
smaller than Ascarids’
Shape：oval, flattened on one side
Color：colorless
Shell： quite thick
Contains：an undeveloped larva
inside
Morphology－ Eggs of hookworms
Shape: oval-round
Shell: thin with smooth
and colorless (transparent)
eggshell
Size: 57-76 µm by 3547 µm
Contains: clear space
between the egg-shell and
the ovum.
Usually 2 to 16 cells in
feces
Morphology－ Eggs of hookworms
Life cycle
Life cycle of Ascaris lumbricoides
Life cycle
Ingested by man
Adult
egg
infective egg
larva
migration
Migration of larva in the host:
Vessels of intestine
liver
heart
(swallowed)
trachea
pharynx
intestine
lungs
Life cycle of hookworm
Life Cycle
Adult
egg
Swallowed
rhabditiform
larva
pharynx
trachea
Penetrate skin
filariform
larva
lung
circulation
Life cycle of
Enterobius vermicularis
Life cycle
(in lumen of cecum)
Adult
egg
ingested
infective egg
Pathogenesis
Pathogenesis of Ascaris lumbricoides
1) larvae: Ascaris Pneumonitis
Asthma
Larva in section of lung
Pathogenesis
2) Adults：
(1) Malnutrition
(2) Disorder of digestive system:
main complaint--- abdominal pain
anorexia (食欲不振)
nausea (恶心)
vomiting (呕吐)
diarrhea (腹泻)
(3) Allergic responses
Complication 并发症
penetrate to bile ducts
胆道蛔虫症
penetrate to the pancreatic and the appendix
胰腺
阑尾
intestinal obstruction 肠梗阻
Ectopic parasitism 异位寄生
Pathogenesis of Enterobius vermicularis
1. cause irritation( pruritus 搔痒) of the anal region
Secondary bacterial infection in areas
scratched raw may occur.
2. vaginitis and rarely salpingitis in young girls.
阴道炎
输卵管炎
3. cause mental anguish
Pathogenesis of hookworm
1. Local dermatitis (ground itch) 钩蚴性皮炎
2.Pulmonary (pneumonia-like) symptoms
(symptoms are not as severe as Ascaris migration)
3. Anemia
a. The worm sucks blood
and the wound oozes blood
A. duodenale takes 0.26 ml/day;
N. americanus 0.03 ml/day
b. The worm usually changes its sucking site
c. Disfunction of intestine to absorb iron
gradually produce an iron-deficiency anemia
4. gastroenteric symptoms 胃肠道症状
Slight, intermittent abdominal pain
5. Aberration of appetite(geophagy 异嗜症) .
loss of normal appetite and desire to eat soil
or un-normal materials
6. Hookworm diseases of infant
7. eosinophilia
Laboratory Diagnosis
Laboratory Diagnosis
1. By identifying the eggs
1. direct fecal smear
2. brine-floatation method
（饱和盐水浮聚法）
3. Scotch tape technique
(cellophane tape impression)
透明胶纸黏贴法
4. Larval cultivation
(钩蚴培养法)
2. By identifying the adults
3. therapeutic test
Epidemiology
distribution
Basic conditions in parasitic epidemiology
 Souce of infection
Patients and infected persons
 Mode of transmission (Factors of prevalence)
For round worm
Warmer and poor sanitation
Via mouth
Inadequate disposal of feces
Using nightsoil as fertilizer
For hookworm
Bare-foot walking
Via skin
Others:
Oral （A. doudenale)
Placenta
Mother’s milk
Paratenic hosts
For pinworm
“Hand-to-Mouth”Transmission
retroinfection through anus
inhalation of ova
 Susceptible population
Epidemiology
the reason for wide distribution of Ascaris l
1. simple life cycle
2. high reproductive capacity (240,000 eggs per day)
3. resistance of egg (due to presence of ascarosidal )
4. social customs and habits
Treatment Prevention and control
Treatment of patients and carriers,
Blockade of the route of transmission
Protection of the susceptible population
(personal prophylaxis)
Chemoprophylaxis, vaccines, other preventive
measures
Treatment Prevention and control
Treatment:
Mebendazole（甲苯哒唑）
Albendazole（阿苯哒唑，肠虫清）
To prevent re-infection of E.v, treat the whole
family.
Others for hookworm diseases?
透热疗法
纠正贫血
Prevention and control:
Good hygiene is the best preventive measure
hygienic control of food, feces
avoidance of contact with infected fecal material
Wash all bed clothes and bedding in hot water to
kill infective eggs of E.v.
Others?
Dog and Cat Hookworms
HUMANS may serve as accidental hosts of these
hookworms when the filariform larvae penetrate human
skin
Creeping
Eruption
匍形疹