Necator americanus
This species, so called American hookworm, is found in predominantly the tropics. The anterior end is hooked against the body curvature. The mouth is provided ventrally and dorsally with cutting plate.
Male:
The male measures 8 cm in length. The posterior end is broadened into a membraneous copulatory bursa, which is provided with two long spicules fused distally.
Female:
The female measures 10 cm in length. The posterior end is straight
Infective stage and methods of infection:
The filariform larva infects by skin penetration.
Adult male and female worms live in the small intestine. The female lays eggs (oval, 60x40 microns), which contain immature embryo in the 4 cell stage. When the eggs pass in the stool to the soil and under favorable conditions of temperature, moisture and oxygen, they hatch into larvae, which molt twice and become infective. When the filariform larvae penetrate the skin, they circulate in the blood, reach the lungs, ascend to the trachea, descend to esophagus to reach the small intestine and become adults.
Pathogenecity
Adult worms in the intestine feed on blood causing iron deficiency anemia. The larvae may cause inflammation of the lungs.
Diagnosis:
Examination of stool by direct saline smear to detect the eggs.
INSTAGRAM
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