Experiment 1

Nematodes

Four species of NematodesFour species of Nematodes ：：

Ascaris lumbricoides （蛔虫） Hookworm （钩虫） Trichuris trichiura ( 鞭虫 )Enterobius vermicularis( 蛲虫）

Ascaris lumbricoidesAscaris lumbricoides

(( 似蚓蛔线虫似蚓蛔线虫 ))

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

Adult worm of A. lumbricoides

The typical curled tail with a pair sickle like copulatory spine readily

distinguishes males.

On the tip of the head there are three lips, arranged as a Chinese word “ 品 ” .

mouth

lip

The lips of Ascaris lumbricoidesThe lips of Ascaris lumbricoides

Scanning electron microscope of the lips of Ascaris lumbricoides

The lips of Ascaris lumbricoidesThe lips of Ascaris lumbricoides

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.

male

female

EggEgg

unfertilized 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. fertilized eggs

Fertilized eggs: 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.

Freshly Passed Ascaris Eggs From Freshly Passed Ascaris Eggs From fecesfeces

The eggs may appear from light to dark brown in color.

Decorticated egg:

Normal fertile eggs may lack the mammillated layer and are referred as decorticated eggs.

larva

Unfertilized eggUnfertilized 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.

Unfertilized and Fertilized EggsUnfertilized and Fertilized Eggs

Diagnosis The symptoms and signs are

for reference only. The confirmative diagnosis depends on the recovery and identification of the worm or its egg.

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.

(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.

Ancylostoma duodenaleAncylostoma duodenale and and Necator americanusNecator americanusAdult

Egg

A.duodenale is larger than N.americanus

A.duodenale likes the letter “C”A.duodenale likes the letter “C”N.americanus likes the letter “S”N.americanus likes the letter “S”

MorphologyMorphology

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.

The Morphological Differences The Morphological Differences between Two species of Hookwormsbetween 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 _______________________________________________________

Ancylostoma duodenaleAncylostoma 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.

Necator americanusNecator americanus

This species contains a pair of semilunar cutting plates on the ventral wall. Scanning electron micrograph

of the oral opening of Necator americanus.

ventral ray

dorsal ray

lateral ray

rounded, dorsal ray tripartitetridigitate at the terminus

Broader than long , dorsal ray small,bipartitebidigitate at the base

A. duodenale N. americanus

Bursa & dorsal rayBursa & dorsal ray

dorsal raydorsal ray

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

Hookworm EggsHookworm 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..

Adults in intestinal mucosa

Intestinal phase: worms attach to the mucosa and feed on blood.

diagnosis

Methods: 1. saturated brine flotation

technique2. direct fecal smear

Trichuris trichiura

毛首鞭形线虫

Adult Egg

MorphologyMorphology

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

Adult:

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.

Egg:

Eggs of T. trichiura under the high power

EggEgg

adult worms deep into the caecal submucosa

diagnosis

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

Enterobius vermicularisEnterobius vermicularis

( 蠕形住肠线虫 )

MorphologyMorphology1. 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.

male female

Enterobius vermicularisEnterobius vermicularis

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

adult

Anterior part of E. vermicularis.

esophageal bulb

Cephalic alae

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

eggegg

50 to 60 µm by 25 µm, colorless and transparent, thick shell, flattened on

one side content is an immature

larva.

The egg of E. vermicularisThe egg of E. vermicularis

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.

Manipulation

Ascaris lumbricoides ： adult, the the lipslips, copulatory spines of malecopulatory spines of male ， the fertilized and unfertilized ova

Hookworm: adult,, Egg Egg ，， adults in adults in intestinal mucosa.intestinal mucosa.

Trichuris trichiura: adult, Egg, adult worms deeply into the caecal submucosa

Enterobius vermicularis: adult, eggegg

ExerciseExercise

Draw the egg of these four nematodes.

Mark the structure of the eggs.

Where can you find the eggs?