Mercury exposure and murine response to Plasmodium yoelii infection and immunization.

Malaria has re-emerged in Amazonia over the past two decades. Many factors have been proposed for this, among them changes in population distribution, failures of vector control and pharmacologic management, and local as well as global environmental changes. Among the latter factors, we have studied the potential role of increasing exposures to the immunotoxic metal mercury, which is widely used in Amazonia for artisanal extraction of alluvial gold deposits. We report here that Hg impairs host resistance to malaria infection at exo-erythrocytic stages. Hg exposed mice have higher parasitemia following infection with sporozoites, but not after transfusion of infected red cells. In mice inoculated with irradiated sporozoites, Hg blocks acquisition of immunity. In addition Hg affects immunologic parameters that are known to be involved in host response to malaria infection. These results have potential implications for the incidence and prevalence of malaria among populations exposed to mercury from artisanal goldmining and consumption of contaminated fish regions with high rates of malaria and other infectious diseases.