Life Cycle of a Hook Worm

Hook worms are a large group of small nematode parasites that infect humans and animals, especially dogs. They can bore into the skin and travel through a body before lodging in the small intestine. Some species of hook worm are Ancylostoma duodenale, Necator americanus and Ancylostoma ceylanicum.

Stage 1

• Hook worm eggs are found in fecal matter.

  Hook worm eggs are found in fecal matter and hatch in a couple of days, emerging as rhabditiform larvae.

Stage 2

• After about a week, they develop into the filariform larvae stage, which is the infective stage. Once the filariform larvae come in contact with a human or animal host, they burrow into the skin and travel through the blood vessels to the heart and lungs of the host.

Stage 3

• The filariform larvae emerge into the lungs of the host and migrate up to the pharynx, where they are swallowed. They travel through the digestive system until they attach themselves to the walls of the small intestine, where they feed and grow into the adult stage.

Stage 4

• The adult-stage parasites can survive in the small intestine for several years, laying eggs that are passed with the host's feces to start the cycle over again.

Geography

• Hookworms are found on most continents.

  Hook worms are very common in warm and moist climates and are found in Asia, Africa, North America, South America and Europe.