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Hookworms

Scientific name. Necator americanus/Ancylostoma duodenale

Common name. New World Hookworm/Old World Hookworm

Disease. necatoriasis/ancylostomiasis

Geographic distribution. Necator americanus : Southeast Asia, India, Sub-Saharan Africa and Tropical America. Ancylostoma duodenale : Northern India, Parkistan, China, Middle East and Northern Africa.

Life cycle. Humans are infected with hookworm when third-stage filariform larvae in soil. They penetrate through the skin, particularly into areas such as unprotected feet. Once infected, the filariform larvae migrate into blood circulation. They break out of the pulmonary blood vessels into alveoli, then crawl up the trachea and are swallowed with saliva to re-enter the intestinal tract. They attach themselves to the mucous membrane of the small intestine to mature into adults.

Morphology. The adults are cylindrical with a head bent sharply backwards giving them a hooked appearance. The average adult hookworm usually measure about 5-10 ㎜ in length by 0.2 to 0.5 ㎜ in width. The hookworm species are mainly differentiated by their buccal capsule and the arrangement of rays in the bursa. The hookworm eggs measure 60-75 ㎛ by 35-40 ㎛. Eggs may be unsegmented or show visible embryonic cleavages, usually two, four or eight cell stages. However, eggs in stool samples that have been kept at room temperature over time may reveal a developing larva.

Pathology and clinical symptoms. Sometimes some itchy papules at the site of larval penetration, ground itch, occurs. Patients with chronic infections may experience vague mild GI symptoms, slight anemia due to loss of blood and weight loss or weakness. In heavy infections, microcytic hypochromic anemia is produced.

Diagnosis. Recovery of the eggs in stool samples.

Prevention. Proper sanitation practices, appropriate fecal disposal, and personal protection by covering bare feet.

Treatment. Mebendazole or albendazole. It should not be given to pregnant women.


Kyoung Hwan Joo


Hookworm egg.

Tai Soon Yong


Hookworm egg.

Tai Soon Yong



Yong Suk Ryang



Yong Suk Ryang


Hookworm eggs in the stool examination from the patient, X450

Yong Suk Ryang


Hookworm, various eggs in the stool examination from the patient, X450

Yong Suk Ryang


Hookworm ova and larva in the stool examination from case, X100

Yong Suk Ryang


Hookworm egg from feces of cat.

Woon-Mok Sohn


Rhabditoidform larva of a hookworm.

Tai Soon Yong