The most common hookworms are Ancylostoma duodenale and Necator americanus. Adults attach to the walls of the jejunum and females lay large numbers of eggs that are passed out with the faeces. The eggs hatch in the soil and infect man by usually burrowing through the soles of the feet. The larvae then migrate to infect the heart and lungs before passing into the tracheae, pharynx and then the small intestine. Strongyloides stercoralis .
Females live in the mucosal glands of the small intestine.
Eggs hatch in these glands and the larvae are passed with the faeces into the soil. As with other hookworms, infection results from the larvae burrowing into the skin. The rest of the life cycle is as for A. duodenale and N. americanus. Adult worms of Ascaris lumbricoides live in the small intestine where they lay large numbers of eggs that are passed out with the faeces. Unlike the hookworms, the eggs are the infectious form in which the larvae develop.