Plasmodium vivax Parasite Load Is Associated With Histopathology in Saimiri boliviensis With Findings Comparable to P vivax Pathogenesis in Humans

Background. Plasmodium vivax can cause severe malaria with multisystem organ dysfunction and death. Clinical reports suggest that parasite accumulation in tissues may contribute to pathogenesis and disease severity, but direct evidence is scarce. Methods. We present quantitative parasitological and histopathological analyses of tissue sections from a cohort of naive, mostly splenectomized Saimiri boliviensis infected with P vivax to define the relationship of tissue parasite load and histopathology. Results. The lung, liver, and kidney showed the most tissue injury, with pathological presentations similar to observations reported from autopsies. Parasite loads correlated with the degree of histopathologic changes in the lung and liver tissues. In contrast, kidney damage was not associated directly with parasite load but with the presence of hemozoin, an inflammatory parasite byproduct. Conclusions. This analysis supports the use of the S boliviensis infection model for performing detailed histopathological studies to better understand and potentially design interventions to treat serious clinical manifestations caused by P vivax.