1. Hookworms (钩虫) Two major species of hookworms can infect human
Necator americanus
(美洲板口线虫)
Ancylostoma duodenale
(十二指肠钩口线虫)

2. General Introduction
Human intestinal nematode of smaller size, inhabit the small intestine
World-wide distribution, about 900 million infections in the world
A. duodenale is prevalent in Southern Europe, North Africa, Northern Asia (North China), and the more pathogenic one
N. americanus is the predominant species in the Western hemisphere and equatorial Africa (South China)
Many areas are endemic for both species
Heavy infection may evoke anemia known as "Yellow Laziness"
It can profoundly affect entire populations by gradually sapping the victims’ strength, vitality, and overall well-being

3. Morphology: Adults Ancylostoma duodenale
Female is mm in length by 0.6 mm in diameter
Males are 8-11 mm by 0.4 mm
Posterior end has an umbrella-shaped bursa with riblike rays
Two pairs of curved teeth on the ventral wall of its buccal capsule

4. Morphology: Adults Necator americanus
Females are 9-11 mm in length by 0.4 mm in diameter
Males are 7-9 mm by 0.3 mm
Smaller than A. duodenale
A pair of semilunar cutting plates on the ventral wall of the buccal capsule

5. Buccal capsule
Ancylostoma duodenale
Necator americanus

6. Morphology: Egg
oval or can-shaped with a thin, hyaline shell, measured by µm.

8. Life cycle

11. Life cycle No intermediate host is necessary
Larva takes a free living mode
The filariform larva is the infective stage
Infection routes: skin penetration(mainly); orally swallow; maternal-child
Residing in human upper small intestine: duodenum, jejunum
Blood-Lung migration: skin --- lymphatic system --- right side of the heart --- lung --- respiratory tree --- coughed up and swallowed --- small intestine
Persisting migrans(迁延移行): Ancylostoma duodenale

12. Pathogenesis 1. Hookworm larvae dermatitis:
Penetration of the skin by the filariform larvae may be asymptomatic in previously uninfected individuals.
However, those experiencing repeated infections develop itching, known as "ground itch" or "dew itch".

13. Pathogenesis
2. Migration of pre-adult cause temporary pulmonary inflammation:
In heavily infected individuals
(i.e., worms), there can be symptoms of pneumonia during the migratory phase in the developmental cycle of these worms

14. Pathogenesis 3. Abdominal pains, diarrhea, loss of appetite… 4. Anemia
Especially in young children
Hypoproteinemic because of some loss of serum proteins
Iron-deficiency

15. 5. Allotriophagy (Geophagy): due to the iron-deficiency
Why the small worms can cause anemia?
The pump-like action when worms suck blood
The worms secrete an anticoagulant, which facilitates bleeding
The worms usually change the sites when suck blood
5. Allotriophagy (Geophagy): due to the iron-deficiency
6. Ancylostomiasis in infant

17. Edema, ascites and loss of labour force

18. Allotriophagy

19. Laboratory diagnosis Brine floatation is the method of first choice
Hookworm larvae cultivation is used for species identification
Hookworm larvae in sputum

20. Epidemiology Most prevalent in the tropical and subtropical zones
In China, mostly mixed infected, while A.duodenale is somewhat northward distributed and N. americanus in southward

21. Epidemiology
Moist, shady, sandy, or loamy soil favors persistence of these worms
Larvae can survive for up to 6 weeks
Do not live long in clay, dry, hard packed soils, or where temperatures are freezing, or are higher than 45C

22. Principles of Control Chemotherapy: Albendazole; Mebendazole
Sanitary disposal of human feces is the most effective control measure in preventing the spread of infection with the hookworms
Protection of the susceptible population