DO BABESIOSIS AND MALARIA SHARE A COMMON DISEASE PROCESS

Clinical confusion between human babesiosis and malaria is often repor ted in the literature. Headache, fever, chills, nausea, vomiting, myal gia, altered mental status, disseminated intravascular coagulation, an aemia with dyserythropoiesis, hypotension, respiratory distress, and r enal insufficiency are common to both diseases. This remarkable simila rity is nor restricted to the human host. In the mouse, for example, t he histological changes wrought by fatal malaria (Plasmodium vinckei) and babesiosis (Babesia rhodaini) are identical, and parasites of both genera cross-protect. Malarial disease pathogenesis is now generally associated with excessive production of pro-inflammatory cytokines, su ch as rumour necrosis factor. While this concept has not yet been exam ined in babesiosis, indirect evidence arises from noting the parasite density at which illness occurs in primary infections caused by either organism. Naive mice tolerate high loads of malarial or babesial para sites before they become ill, and are also tolerant to endotoxicity, w hich is mediated by these same cytokines. In contrast, humans require very much smaller loads of Plasmodium or Babesia spp. before becoming ill, and likewise are very sensitive to endotoxin, the harmful effects of which are mediated by the pro-inflammatory cytokines. For these re asons, as discussed in this review, the diseases caused by these two g enera of intra-erythrocytic protozoan parasites will probably prove to be conceptually identical.