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（美洲板口线虫）and Ancylostoma duodenale（十二指肠钩口线虫）. They live in small intestine.
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
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
Decorticated ascaris egg
Decorticated ascaris egg hookworm egg
Shell thick thin
Egg cell unsegmented 4-8cells
Space between new moon shaped space empty space surrounding
Shell and cell between cell and ends of shell the segmented cells
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
A. lumbricoides Hookworm
Infective stage embryonated egg filariform larvae
route of infection by mouth by skin
mode of infection passively actively
blood-lung pass through the liver don’t pass through the liver
migration in lungs of host, larvae the larvae don’t molt and
molt twice and stay stay in the lungs
food of the adults intestinal content blood
life span 1 year several years
Filariform larvae cavum right heart
lungs(alveolus, bronchiole, bronchus) trachea, pharynx
duodenum adults eggs
outside of the body rhabditiform larvea1
In feces O2, 24hours
rhabditiform larvae2 (L2)
survive 15weeks in warm soil
filariaform(L3) wait for new hosts
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.
(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 (or pica 异嗜症) is due to the lack of trace element iron .
(4) Amenorrhea（闭经）, sterility（不孕）, abortion（流产） may take place in women.
(5) Gastrointestinal bleeding
(6) Infantile hookworm disease
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
1. Albendazole 2. Mebedazole
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
Unified measures: 1. sanitary disposal of night soil, 2. individual protection, 3. health education, 4. cultivate hygienic habits, 5. treat the patients and carriers.
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.
1. 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. .
2. Egg: 50 to 60m by 25 µm, persimmon seed-like, colorless and transparent, thick and asymmetric shell, content is a larva.
Anterior part of E. vermicularis. Note cephalic alae and esophageal bulb .
The cephalic alae are clearly seen at the anterior end. The cuticle and the alae are transversely striated. The oesophageal bulb are also visible.
Egg: 50 to 60m by 25 µm, persimmon seed-like, colorless and transparent, thick and asymmetric shell, content is a larva.
1. site of inhabitation: cecum and colon
2. infective stage: embryonated egg
3. infective route: by mouth
. 4. without intermediate host and reservoir host
5. life span of female adults: 1-2 months
migrate out anus 6hours
Adults eggs on perianal skin embryonated eggs
swallowed by hostlarvae hatch out molt
intestinal lumen adults in cecum
2-4 wks migrate down
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 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
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
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.