The pathophysiology of canine babesiosis: new approaches to an old puzzle.

The haemoprotozoan parasite, Babesia canis, is the cause of an economically important and potentially life-threatening disease of dogs in South Africa, the pathophysiology of which is incompletely understood. Available literature is reviewed, with emphasis on the pathophysiology of the anaemia and complications of babesiosis. The remainder of the review explores the possibility that pathophysiological mechanisms currently being investigated in human malaria and bovine babesiosis (in which, as in canine babesiosis, an intra-erythrocytic parasite causes multi-systemic pathology) might also be active in B. canis infections. The entity referred to as the multiple organ dysfunction syndrome is discussed as a proposed mechanism within which apparently unrelated aspects of babesiosis form a predictable pattern. The molecular mediators of multiple organ dysfunction, including cytokines, nitric oxide and free oxygen radicals, are generated by host tissues, and are now under active study to help elucidate the pathophysiology of malaria. The similarities between the manifestations of different diseases in different host species can be explained by the concept that the disease process is largely mediated by these molecules, generated by the host in response to the parasite, rather than arising directly from the parasite itself. The current direction of malaria research provides a basis for future research into the pathophysiology of canine babesiosis.