introduction to the helminths 蠕虫 helminths means worms, multicellular organisms. phylum class...
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Introduction to the Helminths 蠕虫
Helminths means worms, multicellular organisms.
Phylum Class
Nemathelminthes Nematoda(round worm) 线虫纲 线形动物门 Platyhelminthes Tremetoda(flatworms) 吸虫纲 扁形动物门 Cestoda 绦虫纲
The Nematodes 线虫 There are many, many nematodes
2006 诺贝尔奖 : RNA干扰机制
2002 年诺贝尔奖:程序性细胞死亡
C.Elegans
MorphologyMorphology
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
Holomyarian type( Whipworm)
Polymyarian type ( Ascarids)
Meromyarian type (Hookworm)
The arrangement of the somatic muscles
Digestive system
Mouth pharynx esophagus
intestine anus
咽管 食管
肠管 肛门
Reproductive system
male reproductive system
Testis seminal vesicle 睾丸 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 and2 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 M2 M3 M4 Egg L1 L2 L3 L4 Adult larva (male & female)
Kinds of life cycle in nematodes
Ascaris lumbricoides Trichuris trichiura Enterobius vermicularis Hookworms
Indirect life cycle: intermediate host is necessary
Trichinella spiralis Filaria
Direct life cycle: Intermediate host is not necessary
土源性线虫(肠道线虫)
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) 似蚓蛔线虫Trichuris trichiura (whipworm) 毛首鞭形线虫 Enterobius vermicularis (pinworm) 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 美洲板口线虫Ancylostma ceylanicum 锡兰钩口线虫Ancylostma caninum 犬钩口线虫Ancylostma brazilience 巴西钩口线虫
Adult live in the intestine and take blood from the host, cause hookworm disease.
Number of humans infected is estimated at 1.2 billion with 50,000 to 60,000 deaths each year.
国内: 6.12%
Enterobius vermicularis(Pinworm)
Almost anybody can
become infected with
this
parasite , especially
children.
The worldwide infection is about 210 million
国内: 10.28%
Morphology
Morphology - Adult of Ascaris lumbricoides
the largest nematode parasites of humans
Creamy white or pinkish in color
elongate and cylindrical
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 Ascaris lumbricoides
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 Trichuris trichiura
Morphology - Adults of Enterobius vermicularis
Adults: pin-like, white, small worm
Female showing esophageal bulb & cephalic alae
Male with curved posterior end, Female has a long pointed end.
咽管球 头翼
Morphology - Adults of hookworms
Adult: Slender, pinkish or creamy-gray in color, about 10mm in length.
Females:9-13 mm long with egg-filled uterus Males:7-11 mm long, Posterior
end forms a Copulatory bursa ( 交合伞 )
Morphology - Adults of hookworms
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.
shape “c”, 1cm± “s”, 1cm±
buccal capsule flat and oval-shape oval-shape two pairs one pair cutting plates
Copulatory bursa round oblate
spicule two, separated two, fused at their ends
A.duodenale N. americanus
Difference between A.duodenale and N. americanus
Morphology - larva of hookworms
rhabditiform Larva 杆状蚴 filariform larva : infective stage
Eggs are unembryonated when passed in the feces. Embryonation occurs in the soil.
Unembryonated egg in feces
broadly oval
yellowish to brown in color
Thick shell
ovum
protein coat
fertilized
Morphology - Eggs of Ascaris lumbricoides
unfertilized and fertilized egg
Decorticated egg(lost outer albuminous
coating)
Embryonated egg in soil
Morphology - Eggs of Ascaris lumbricoides
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
Shape: oval-round Shell: thin with smooth
and colorless (transparent) eggshell
Size: 57-76 µm by 35-47 µm
Contains: clear space between the egg-shell and the ovum.
Usually 2 to 16 cells in feces
Morphology - Eggs of hookworms
Morphology - Eggs of hookworms
Life cycle
Life cycle of Ascaris lumbricoides
Adult egg infective egg larva
Ingested by man
migration
Life cycle
Migration of larva in the host:
Vessels of intestine liver heart lungs
trachea pharynx intestine(swallowed)
Life cycle of hookworm
Life Cycle
Adult egg rhabditiform filariform larva larva Swallowed pharynx trachea lung circulation
Penetrate skin
Life cycle of Enterobius vermicularis
Life cycle
ingested
Adult egg infective egg
(in lumen of cecum)
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
(3) Allergic responses
anorexia ( 食欲不振 ) nausea ( 恶心 )
vomiting ( 呕吐 ) diarrhea ( 腹泻 )
Complication 并发症
penetrate to bile ducts
penetrate to the pancreatic and the appendix
胆道蛔虫症
胰腺 阑尾
intestinal obstruction 肠梗阻
Ectopic parasitism 异位寄生
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 Enterobius vermicularis
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
Patients and infected persons
Souce of infection
Mode of transmission (Factors of prevalence)
For round worm
For hookworm
Via mouth
Warmer and poor sanitation
Inadequate disposal of feces
Using nightsoil as fertilizer
Via skin
Bare-foot walking
Others:Oral ( A. doudenale)PlacentaMother’s milkParatenic hosts
Susceptible population
“Hand-to-Mouth”Transmission
retroinfection through anus
inhalation of ova
For pinworm
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:
hygienic control of food, feces
Good hygiene is the best preventive measure
Wash all bed clothes and bedding in hot water to
kill infective eggs of E.v.
avoidance of contact with infected fecal material
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