Hookworm

The hookworms cause hookworm disease, which is one of the five major parasitic disease in China(malaria, shistosomiasis, filariasis, kala- azar and hookworm disease). At least two species of hookworms infect man, Necator americanus and Ancylostoma duodenale. They live in small intestine.

Morfology

Adults: They look like an odd piece thread and are about 1cm. They are white or light pinkish when living. ♀is slightly larger than♂.The male’s posterior end is expanded to form a copulatory bursa.

Eggs: 60×40 µm in size, oval in shape, shell is thin and colorless.

Content is 2-8cells.

The Morphological Differences between Two species of Hookworms

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A. duodenale N. americanus

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Size larger smaller

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Shape single curve, looks like C double curves, looks like S

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Mouth 2 pairs of ventral teeth 1peir of ventral cutting plates

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Copulatory circle in shape oval in shape

Bursa (a top view) (a top view)

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Copulatory 1pair with separate 1pair of which unite to form

spicule endings a terminal hooklet

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caudal spine present no

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vulva position post-equatorial pre-equatorial

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Lyfe cycle

1. Final host: man

2. Inf. Stage: Larva 3 or filariform larva

3. Inf. Route: by skin

4. Food: blood and tissue fluid

5. Site of inhabitation: small intestine

6. Life span: Ad 15years, Na 3-7years

7. Blood-lung migration:

skin, cavum, right heart, lungs

nPathogenesis & Clinical manifestation

Larval migration

(1) Dermatitis, known as "ground itch" or "stool poison".The larvae penetrating the skin cause allergic reaction, petechiae 0r papule with itching and burning sensation. Scratching leads to secondary infection.

(2) pneumonitis (allergic reaction), Loeffier's syndrome: cough, asthma, low fever, biood-tinged sputum or hemoptysis, chest-pain, inflammation shadows in lungs under X-ray. These manifestations go on about 2 weeks.

Adults in small intestine

(1) Epigastric pain as that of a duodenal ulcer.

(2) A large worm burden results in microcytic hypochromatic anemia (character manifestation). The symptoms are lassitude, edema, palpitation of the heart. In severe case, death may result from cardiac failure or physical exhaustion.

(3) Allotriophagy (orpica) is due to the lack of trace element iron (4) Amenorrhea, sterility, abortionmay take place in women.

(5) Gastrointestinal bleeding

(6) Infantile hookworm disease

Diagnosis

Criterion: 1. hemoglobin is lower than 120g/L in man, 110g/L in woman. 2. find hookworm egg

Method:

1. saturated brine flotation technique

2. direct fecal smear

3. culture of larvae

Treatment

1. Albendazole
2. Mebedazole

Epidemiology

worldwide distribution. 22-26℃ is the optimal temperature for Ancylostoma duodenale development, Ancylostoma duodenale mainly prevalent in north of China. 31-35℃ is suitable for Necator americanus, it is mainly prevalent in south of China

Prevention

Unified measures:
1. sanitary disposal of night soil,
2. individual protection,
3. health education,
4. cultivate hygienic habits,
5. treat the patients and carriers.

Enterobius vermicularis (Pinworm)

The pinworms are one of the most common intestinal nematodes. The adult worms inhabit the cecum and colon. Right after mating, the male dies. Therefore, the male worms are rarely seen. The female worms migrate out the anus depositing eggs on the perianal skin. Humans get this infection by mouth and by autoinfection.


Morfology

Adults: The adults look like a pin and are white in color. The female worm measures about 8 to 13 mm in size and is fusiform in shape. The male adult is only 2-5mm. The tail of a male is curved. They die right after mating, thus males are rarely seen. The anterior end tapers and is 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.

Egg: 50 to 60m by 25 µm, persimmon seed-like, colorless and transparent, thick and asymmetric shell, content is a larva.Anal smear showing large numbers of Enterobius eggs under the lower power. In the background are also two Ascaris eggs.

Life cycle

site of inhabitation: cecum and colon , infective stage: embryonated egg and infective route: by mouth, without intermediate host and reservoir host, life span of female adults: 1-2 months.

About one-third of pinworm-infected persons are asymptomatic, The adult worms may cause slight irritation of the intestinal mucosa.

Major symptom is anal pruritus, which associates with the nocturnal migration of the gravid females from the anus and deposition of eggs in the perianal folds of the skin. Restlessness, nervousness, and irritability, probably resulting from poor sleep associated with anal pruritus,. In young girls, migration of the worms may produce vaginitis and salpingitis or granuloma of the peritoneal cavity.

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.

Treatment & Prevention

Since the life span of the pinworm is less than two months, the major problem is reinfection. Albendazole is the drug of choice. Repeated retreatment may be necessary for a radical cure.

Prevention:
1. treat the patients and carriers
2. individual health
3. public health
4. health education and hygienic habits

Epidemiology

Geographical distribution—cosmopolitan in temperate zones with about 30 to 50% of the population infected. It is more common in white than colored people and more prevalent in children than adults. Enterobiasis is most common where people live under crowded conditions such as orphanages, kindergartens, and large families.

Trichuris trichiura

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. The male is smaller than the female and has a curved tail. The reproductive organs of male and female are all double tubule.

Egg: it is barrel or spindle in shape and 50 x 20µm in size. It is brownish and has a translucent polar plug at either ends. The content of the egg is an undeveloped cell


Life cycle

Female releases 1000 to 7000 unembryonated double-plugged eggs each day.Eggs are deposited onto warm, moist shady soil where they embryonate to the L1 stage.

The emrionate egg is the infective stage and is ingested. L1 hatch from the egg in the small intestine and burrow into the mucosa where they are. Adults migrate to the ileocecal and colon regions. Adult worm is inserted into the wall of the intestine penetrating through the mucosa and into the submucosa where blood is ingested.

Pathogenesis:

1.Light infection: Asymptomatic

2.Middle infection: Clinical manifestations are usually abdominal pain, anorexia, diarrhea, constipation .

3. Heavy infection: Bloody diarrhea, emaciation, prolapse of the anus may occur.

Diagnosis:

Discover the eggs in feces by saturated brine flotation method or direct fecal smear.

Treatment and prevention: Same as those of ascariasis Take Mebendazole 3 days for a treatment course and repeat next week