Hookworms

Hookworms

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.

I.   Morphology

1. 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.

2. Eggs: 60×40 µm in size, oval in shape, shell is thin and colorless. Content is 2-8cells.

Adults of A. duodenale

Adults of N. americanus

Differences between two hookworms

Scanning electron micrograph of the mouth capsule of Ancylostoma duodenale, note the presence of four "teeth," two on each side.

Scanning electron micrograph of the mouth capsule of Necator americanus, another species of human hookworm. Note the presence of two cutting "teeth“.

Ancylostoma duodenale - copulatory bursa and spines of male(a side view)

Copulatory bursa of N. americanus(a side view)

Left picture: Copulatory bursa and spines of N. americanus(a side view); Right picture: copulatory bursa of A. duodenale(a top view)

Morphologically it is not possible to differentiate between A. duodenale and N. americanus. Interference contrast. ×400. Enlarged by 5.4.

3.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 1peir 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 _______________________________________________________

II. Life 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

Life cycle of hookworm

III. Pathogenesis and Clinical Manifestations

1. 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.

2. Adults in small intestine (1) Epigastric pain as that of a duodenal ulcer. (2) A large worm burden results in microcytic hypochrom

atic 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

Adults in intestinal mucosa

Iv. Diagnosis

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

Method: 1. saturated brine flotation technique2. direct fecal smear3. culture of larvaeV. Treatment1. Albendazole 2. MebedazoleVI. Epidemiology worldwide distribution. 22-26℃ is the optimal temperature for Ancylosto

ma 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

VII. PreventionUnified measures: 1. sanitary disposal of night soil, 2. individual protectio

n, 3. health education, 4. cultivate hygienic habits, 5. treat the patients and carriers.