Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. These species are found throughout the tropics and subtropics.Most people who are infected are asymptomatic. The most significant risk of hookworm infection is anemia secondary to loss of iron into the gut.
Hookworm larvae emerge from passed eggs within 24 hours. Molt to an infective filariform larval stage in another 24 hours. After molting, larvae are able to penetrate intact skin. Walking barefoot in soil contaminated with feces - most common method of exposure.
After skin penetration, the venous circulation carries larvae to the pulmonary bed, where they lodge in pulmonary capillaries. Within 3-5 days, the larvae break through into alveoli & travel up from the lungs into the bronchi, the trachea, and the pharynx. Upon reaching the pharynx, larvae are swallowed and gain access to the GI tract. Once in the GI tract, worms attach to the wall of the intestine and begin to feed on the blood of the host. Chronic loss of blood and serum proteins leads to hookworm anemia and impaired nutrition.
Though rare, hookworm infestation should be suspected as a cause of gastrointestinal bleeding in infants in communities with a high risk of infestation. Prognosis is excellent with proper antihelminthic treatment.