Necator americanus

Necator americanus A Human Hookworm, New World Hookworm	Contents	Rev 10/21/2025
	Classification	Biology and Ecology
	Morphology and Anatomy	Life Cycle
Return to Necator menu		Ecosystem Functions and Services
	Distribution	Management
Return to Ancylostomatidae Menu	Feeding	References
	Go to Nemaplex Main Menu	Go to Dictionary of Terminology

Classification:

Phylum: Nematoda
Class: Chromadorea
Order: Rhabditida

Superfamily: Ancylostomatoidea

Family: Ancylostomatidae

Necator americanus Stiles, 1903

Morphology and Anatomy:

Buccal cavity with two dorsal and two ventral cutting plates on the anterior margin, also a pair of subdorsal teeth and a pair of subventral teeth
Body length 9-11 mm females, 7-9 mm males.


	Adult female and male hookworms; tooth-like plates in the stoma of hookworms
Males:	Female:
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

Distribution:

Common in tropical and subtropical climates.

More than a billion people are infected with at least one species. The most important nematode infections of the human gastrointestinal tract are the intestinal roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura), and hookworm (Necator americanus or Ancylostoma duodenale).

It is common for a single individual, especially a child living in a less developed country, to be chronically infected with all three of the nematode parasites, which results in malnutrition, stunted growth stunting, retarded intellectual development, and cognitive and educational deficiencies.

Hosts:

Human.

Contact with soil contaminated with eggs or larvae of nematode parasites is a common form of transmission that results in human infection. The nematodes can live for years as adults in the human intestinal tract. Soil becomes contaminated by fecal material of infected humans and other animal hosts.

Human males are more frequently infested than females, probably through more frequent probability of exposure through labor and recreation.

Larvae penetrate the uninfected skin and travel through respiratory tract and lymph nodes. From there they enter the blood, lungs, and intestines.

Pigs may be an alternate host.

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Feeding:

Larvae penetrate the uninfected skin and travel through respiratory tract and lymph nodes. From there they enter the blood, lungs, and intestines.

If larvae fail to traverse the dermis and they may remain trapped in the skin. That causes skin irritation and cutaneous larval migrans. Other symptoms include excessive coughing and shortness of breath during larval migration.

Once attached to the intestinal wall, N. americanus resides and matures into adults, penetrates blood vessels, and sucks blood.

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Biology and Ecology:

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Life Cycle:

Adult hookworms (Ancylostoma duodenale and Necator americanus) parasitize the upper part of the human small intestine, whereas Ascaris lumbricoides parasitize the entire small intestine and adult Trichuris trichiura live in the large intestine, especially the caecum.

The parasites can live for 3-5 years in the human gastrointestinal tract. After mating, each adult female produces thousands of eggs per day; eggs leave the body in the feces (Roberts et al., 2010).

Eggs in soil hatch after 24ï¿½48 hours under favorable conditions
First juvenile stage J1 is a rhabditiform larva which grows and molts in soil to a J2. The J2 probably feed on microbes in soil and fecal material.
The J2 grows and molts to a J3 infective filariform stage which is able to penetrate human skin, travel through the blood vessels and heart, and reach the lungs.
In the lungs, the filariform larva migrates through pulmonary alveoli and up through the trachea where it is swallowed and carried to the small intestine.
The larva attaches to the intestinal wall, matures into an adult which mates and the famles commence producing eggs.
Adults live in the lumen of the intestinal wall cause damage to the tissues and blood loss.
Eggs produced by the adults are dposited to the soil in feces. the feces; female hookworms produce up to 30,000 eggs per day (Hotez et al., 2005)
Although they can live for 3-5 years, most adult hookworms worms are eliminated in 1-2 years.

Life cycle from SusanA Secretariat - https://www.flickr.com/photos/gtzecosan/15647441559/in/set-72157648845463939, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=36876125

Note: The N. americanus lifecycle only differs slightly from that of Ancylostoma duodenale. N. americanus has no development arrest in immune hosts and it must migrate through the lungs

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click	If species level data are not available, click for genus level parameters

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Ecosystem Functions and Services:

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Management:

Infections of N. americanus are commonly treated with benzimidazoles which kill adult worms by binding to the β-tubulin of the nematode and consequently inhibit microtubule polymerization within the parasite.

Infection and transmission of others can be prevented by not defecating outdoors or using human feces as fertilizer.

This parasite is not transmittable directly from person to person.

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References:

Bethony, J., Brooker, S., Albonico, M., Geiger, S.M., Loukas, A., Diemert, D., Hotez, P.J. 2006. Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. The Lancet 9521:1521-1532.

Hotez, P.J, Bethony, J. Bottazzi, M.E.; Brooker, S., Buss, P. 2005. Hookworm: "The Great Infection of Mankind. PLOS Medicine. 2 (3): e67. doi:10.1371/journal.pmed.0020067

Roberts, L.S.; Janovy, J.; Schmidt, G.D. 2010. Foundations of Parasitology (8th ed.). McGraw-Hill. pp. 472-473. ISBN 978-0071311038