1. Experiment 1
Nematodes

2. Four species of Nematodes：
Ascaris lumbricoides（蛔虫）
Hookworm （钩虫）
Trichuris trichiura (鞭虫 )
Enterobius vermicularis(蛲虫）

3. Ascaris lumbricoides (似蚓蛔线虫)

4. Morphology of adults
The adults are cylindrical in shape, creamy-white or pinkish in color.
The female averages 20-35cm in length. The male is smaller, averaging 15-31cm in length and distinctly more slender than the female

5. Adult worm of A. lumbricoides

6. The typical curled tail with a pair sickle like copulatory spine readily distinguishes males.

7. The lips of Ascaris lumbricoides
On the tip of the head there are three lips, arranged as a Chinese word “ 品 ”.
mouth
lip
The lips of Ascaris lumbricoides

8. The lips of Ascaris lumbricoides
Scanning electron microscope of the lips of Ascaris lumbricoides

9. They have a complete digestive tract. Reproductive organs are tubular
They have a complete digestive tract. Reproductive organs are tubular. male has a single reproductive tubule. The female has two reproductive tubules and the vulva is ventrally located at the posterior part of the anterior 1/3 of the body.

10. female
male

11. There are two kind of the eggs
There are two kind of the eggs. They are fertilized eggs and unfertilized eggs. We usually describe an egg in 5 aspects: size, color, shape, shell and content.
Egg
fertilized eggs
unfertilized eggs.

12. Fertilized eggs:
broad oval in shape, brown in color, an average size 60× 45µm.
The shell is thicker and consists of ascaroside, chitinous layer, fertilizing membrane and mammillated protein coat outside of egg shell The content is a fertilized ovum.
There is a new-moon shaped clear space at the each end inside the shell.

13. Freshly Passed Ascaris Eggs From feces
The eggs may appear from light to dark brown in color.

14. Decorticated egg:
Normal fertile eggs may lack the mammillated layer and are referred as decorticated eggs.

15. larva

16. Unfertilized egg Longer and slender than a fertilized egg.
The chitinous layer and protein coat are thinner.
The content is made of many refractable granules various in size.

17. Unfertilized and Fertilized Eggs

18. Diagnosis
The symptoms and signs are for reference only. The confirmative diagnosis depends on the recovery and identification of the worm or its egg.

19. 1. Ascaris pneumonitis: Examination of sputum for Ascaris larvae is sometimes successful.
2. Intestinal ascariasis: Feces are examined for the ascaris eggs.
(1) Direct fecal film: It is simple and effective. The eggs are easily found using this way due to a large number of the female oviposition, approximately 240,000 eggs per worm per day. So this method is the first choice.

20. (2) Brine-floatation method:
(3) Recovery of adult worms: When adults or adolescents are found in feces or vomit and tissues and organs from the human infected with ascarids , the diagnosis may be defined.

21. Ancylostoma duodenale and Necator americanus
Adult
Egg
A.duodenale likes the letter “C”
N.americanus likes the letter “S”
A.duodenale is larger than N.americanus

22. Morphology
Adults: ＊ Cylindrical with the head bent sharply backwards, look like a hook, about 1cm. ＊ They are white or light pinkish when living. Female is slightly larger than male. ＊The male’s posterior end is expanded to form a copulatory bursa. 22

23. The Morphological Differences between Two species of Hookworms
A. duodenale N. americanus ______________________________________________________ Size larger smaller Shape single curve, looks like C double curves, looks like S Mouth 2 pairs of ventral teeth 1pair of ventral cutting plates ____________________________________________________________ Copulatory circle in shape oval in shape Bursa (a top view) (a top view) Copulatory 1pair with separate 1pair of which unite to form spicule endings a terminal hooklet _______________________________________________________ caudal spine present no vulva position post-equatorial pre-equatorial

24. Ancylostoma duodenale
Note the presence of two pairs of “curved teeth” on the ventral wall , two on each side.
Scanning electron micrograph of the oral opening of Ancylostoma duodenale.

25. Necator americanus
This species contains a pair of semilunar cutting plates on the ventral wall. 
Scanning electron micrograph of the oral opening of Necator americanus.

26. Bursa & dorsal ray rounded, dorsal ray tripartite
ventral ray
lateral ray
dorsal ray
rounded,
dorsal ray tripartite
tridigitate at the terminus
Broader than long ,
dorsal ray small,bipartite
bidigitate at the base
A. duodenale
N. americanus

27. dorsal ray
dorsal ray of A. duodenale
dorsal ray of N. americanus

28. Hookworm Eggs 60×40 µm in size, oval in shape,
shell is thin and colorless.
content is 2,4 or 8 cells.
a clear space is always present between the cells and the egg shell.
×400. Enlarged
Morphologically it is not possible to differentiate eggs between A. duodenale and N. americanus..

29. Adults in intestinal mucosa
Intestinal phase: worms attach to the mucosa and feed on blood.

30. diagnosis
Methods:
1. saturated brine flotation technique
2. direct fecal smear

31. Trichuris trichiura
毛首鞭形线虫
Adult
Egg

32. Morphology
Adult:
The worm looks like a buggy whip, the anterior 3/5 is slender and the posterior 2/5 is thick.
It is pinkish gray in color.
The female worm is 3-5 cm in length and has a long slender esophageal region.
. Both male and female have a single reproductive tubule

34. Egg:
It is barrel or spindle in shape and 50 x 20µm in size. It is brownish and double shelled.
has a transparent polar plug at either ends.
The content of the egg is an undeveloped cell.
Eggs of T. trichiura under the high power

35. Egg

36. adult worms deep into the caecal submucosa

37. diagnosis
Discover the eggs in feces by floatation method or direct fecal smear.

38. Enterobius vermicularis
(蠕形住肠线虫)

39. Morphology Adults: Look like a pin and are white in color.
The female worm measures about 8-13 mm , have a pointed tail.
The male adult is only 2-5mm and the tail curved. They die right after mating, thus males are rarely seen.
At the anterior end , flanked on each side by cuticular extensions called “ cephalic alae”.
The esophagus is slender, terminating in a prominent posterior bulb , which is called “esophageal bulb”.
The cephalic alae and esophageal bulb are important in
identification of the species.

40. Enterobius vermicularis
male
female
Enterobius vermicularis

41. adult
The cephalic alae are clearly seen at the anterior end. The cuticle and alae are transversely striated. The esophageal bulb are also visible.

42. Anterior part of E. vermicularis.
Cephalic
alae
esophageal bulb
Anterior part of E. vermicularis.

43. Scanning electron micrograph of anterior part of E. vermicularis. ×2000.

44. egg 50 to 60 µm by 25 µm, colorless and transparent,
thick shell, flattened on one side
content is an immature larva.

45. The egg of E. vermicularis

46. Diagnosis
Diagnosis depends on recovery of the characteristic eggs. The eggs and the female adults can be removed from the folds of the skin in the perianal regions by the use of the cellophane tape method. The examination should be made in the morning, before the patient has washed or defecated.

47. Manipulation
Ascaris lumbricoides ： adult, the lips, copulatory spines of male ，the fertilized and unfertilized ova
Hookworm: adult, Egg ，adults in intestinal mucosa.
Trichuris trichiura: adult, Egg, adult worms deeply into the caecal submucosa
Enterobius vermicularis: adult, egg

48. Exercise Draw the egg of these four nematodes.
Mark the structure of the eggs.
Where can you find the eggs?