Eosinophilia following treatment of patients with schistosomiasis mansoni and Bancroft's filariasis.

Eosinophilia is frequently observed after treatment of patients with infections due to parasitic helminths. For definition of the characteristics and causes of post-treatment eosinophilic responses, 47 patients with Bancroft's filariasis, who were treated with diethylcarbamazine, and eight patients with schistosomiasis mansoni, who were treated with niridazole, were studied. After therapy for eight days, both groups developed significant (P less than 0.05) increases in their levels of eosinophilia, which peaked in two to four weeks. Maximal levels averaged two and one-half to three time the levels before treatment. Before therapy the number of circulating eosinophils was unrelated to intensity of infection in both groups, but after treatment, when the same relationship was examined in the larger group (the patients with filariasis), the degree of post-treatment eosinophilia was significantly correlated with the patients' worm burdens before treatment (r = 0.727; P less than 0.001). Thus, treatment of helminthic infections can provide a unique opportunity for studying eosinophil responses of humans to graded doses of antigen and has shown that acute responses are determined quantitatively by the amount of antigen initially presented to the host.