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 mercur
y, which is widely used in Amazonia for artisanal extraction of alluvial go
ld deposits. We report here that Hg impairs host resistance to malaria infe
ction at exo-erythrocytic stages. Hg exposed mice have higher parasitemia f
ollowing infection with sporozoites, but not after transfusion of infected
red cells. In mice inoculated with irradiated sporozoites, Hg blocks acquis
ition of immunity. In addition Hg affects immunologic parameters that are k
nown to be involved in host response to malaria infection. These results ha
ve potential implications for the incidence and prevalence of malaria among
populations exposed to mercury from artisanal goldmining and consumption o
f contaminated fish regions with high rates of malaria and other infectious
diseases.