1. 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

2. 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
over 500,000 species have been described. Majority of nematodes are free-living in every conceivable habitat.
C.Elegans

3. 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

4. The arrangement of the somatic muscles
Polymyarian type
( Ascarids)
Meromyarian type
(Hookworm)
Holomyarian type
( Whipworm)

5. Digestive system 咽管 食管
Mouth pharynx esophagus
intestine anus 肠管 肛门

6. Reproductive system male reproductive system Testis seminal vesicle
睾丸 储精囊
vas deferens
输精管
ejaculatory duct
射精管

7. 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

8. nervous system Consist of : circumesophageal nerve ring 咽管神经环 and
2 or 4 longitudinal nerve trunks
神经干

9. Excretory system Excretory pore is anterior. 排泄孔
No flame cells are present.

10. life cycle larva (male & female) M1 M2 M3 M4 Egg L1 L2 L3 L4 Adult
虫卵是否排出体外，排出方式，是否需要在外界发育，是否有感染性？
2.幼虫在哪发育？是否有感染性？幼虫移行与否?是否造成宿主损伤？
3.成虫寄生部位？损害宿主的方式？存活时间，产卵量？

11. 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

12. 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？

13. 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

15. 2004年第二次寄调

16. 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%

17. Hookworms Ancylostma ceylanicum 锡兰钩口线虫 Ancylostma caninum 犬钩口线虫
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.

18. 国内： 6.12%
Number of humans infected is estimated at 1.2 billion with 50,000 to 60,000 deaths each year.

19. Enterobius vermicularis
(Pinworm)
Almost anybody can become infected with this parasite，especially children.
Once one person, usually a child becomes infected, other family members will undoubtedly also become infected.
国内：10.28%
The worldwide infection is about 210 million

20. Morphology

21. Morphology－ Adult of Ascaris lumbricoides
the largest nematode parasites of humans
Creamy white or pinkish in color
elongate and cylindrical

22. Morphology－ Adults of Ascaris lumbricoides
Female: measuring 35cm long, posterior end is straight
Male: measuring 25cm long， posterior end is curved .

23. Morphology－ Adults of Ascaris lumbricoides
Three lips around the mouth in “品”type and possess small teeth

24. 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

25. 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.

26. Morphology－ Adults of hookworms
Slender, pinkish or creamy-gray in color, about 10mm in length.

27. 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)

28. 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

29. Morphology of Necator americanus
Buccal capsule contains a pair of ventral and dorsal cutting plates.
Copulatory bursa contains spicules that are fused distally.

30. two pairs one pair cutting plates spicule two, separated two, fused at
Difference between A.duodenale and N. americanus
A.duodenale N. americanus
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

31. Morphology－ larva of hookworms
rhabditiform Larva 杆状蚴
filariform larva : infective stage

32. 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

33. (lost outer albuminous coating)
Morphology－ Eggs of Ascaris lumbricoides
Embryonated egg in soil
Decorticated egg
(lost outer albuminous coating)

34. Morphology－ Eggs of Trichuris trichiura
size: µm by µm,
smaller than Ascarids’ Shape：a typical barrel
Color：yellow-brown
unstained two polar plugs
Shell： quite thick
Contains： unembryonated
egg

35. 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

36. Morphology－ Eggs of hookworms
Shape: oval-round
Shell: thin with smooth and colorless (transparent) eggshell
Size: µm by µm
Contains: clear space between the egg-shell and the ovum.
Usually 2 to 16 cells in feces

37. Morphology－ Eggs of hookworms

38. Life cycle

39. Life cycle of Ascaris lumbricoides

40. Life cycle migration Vessels of intestine liver heart lungs
Ingested by man
Adult egg infective egg larva
migration
Migration of larva in the host:
鞭虫的生活史与蛔虫相似，有哪些不同？
Vessels of intestine liver heart lungs
(swallowed)
trachea pharynx intestine

41. Life cycle of hookworm

42. Life Cycle Adult egg rhabditiform filariform larva larva
Swallowed pharynx trachea lung circulation
Penetrate skin

43. Life cycle of Enterobius vermicularis

44. Life cycle
(in lumen of cecum)
Adult
egg
infective egg
ingested

45. Pathogenesis

46. Pathogenesis of Ascaris lumbricoides
larvae:
Ascaris Pneumonitis
Asthma
Larva in section of lung

47. main complaint--- abdominal pain
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)
间歇性腹痛，脐周最明显
(3) Allergic responses

48. Complication 并发症 penetrate to bile ducts 胆道蛔虫症
penetrate to the pancreatic and the appendix 胰腺 阑尾

49. intestinal obstruction 肠梗阻
通常视肠道情况采取内科保守治疗（解痉）和手术治疗等方法

50. Ectopic parasitism 异位寄生

52. Pathogenesis of Enterobius vermicularis
1. cause irritation( pruritus 搔痒) of the anal region
Secondary bacterial infection in areas scratched raw may occur.
vaginitis and rarely salpingitis in young girls.
阴道炎 输卵管炎
3. cause mental anguish

54. 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)

55. and the wound oozes blood
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
 Hookworms are very wasteful, as most of the blood taken simply passes through its intestine but is lost to the host.

56. b. The worm usually changes its sucking site
c. Disfunction of intestine to absorb iron
gradually produce an iron-deficiency anemia
Patients with heavy infections may lost up to 200 ml of blood per day

57. gastroenteric symptoms 胃肠道症状
Slight, intermittent abdominal pain
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

58. Laboratory Diagnosis

59. Laboratory Diagnosis 1. By identifying the eggs (钩蚴培养法)
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)

60. 2. By identifying the adults
3. therapeutic test

61. Epidemiology distribution Basic conditions in parasitic epidemiology
Souce of infection
Patients and infected persons

62. Mode of transmission (Factors of prevalence)
For round worm
Warmer and poor sanitation
Inadequate disposal of feces
Using nightsoil as fertilizer
Via mouth
For hookworm
Bare-foot walking
Via skin
Others:
Oral （A. doudenale)
Placenta
Mother’s milk
Paratenic hosts

63. “Hand-to-Mouth”Transmission retroinfection through anus
For pinworm
“Hand-to-Mouth”Transmission
retroinfection through anus
inhalation of ova
Susceptible population

64. 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

65. 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

66. Treatment Prevention and control
Mebendazole（甲苯哒唑）
Albendazole（阿苯哒唑，肠虫清）
To prevent re-infection of E.v, treat the whole family.
透热疗法
纠正贫血
Others for hookworm diseases?

67. 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?

68. 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