Hookworm disease: host-pathogen biology.

The hallmark of hookworm infection, a common helminthic disease, is iron deficiency anemia. The development of anemia is dependent on the intensity of infection, the species of hookworm, and the ability of the host to resist infection and to maintain adequate stores of iron. When conditions are appropriate, the incidence of anemia caused by hookworm is high and has a significant economic impact since it results in a reduction of worker productivity. Loss of blood is caused by direct ingestion of red cells and by tissue trauma produced by worm attachment and feeding. This focal trauma may involve multiple villi and is characterized by local hemorrhage, tissue cytolysis, and neutrophilic response. Although focal intestinal lesions are apparent, their significance is questionable since diffuse mucosal changes are absent in intestinal biopsies of patients with heavy hookworm infection. Short-range control measures protecting against hookworm infection have not succeeded. Development of a vaccine against hookworm infection in humans is problematic since functional protective immunity in humans has not yet been demonstrated and no suitable animal model of hookworm infection in humans is available. At present, the most effective method of intervention appears to be supplementation of food staples with iron.