PARASITE LOCALIZATION AND DISSEMINATION IN THE BABESIA-INFECTED HOST

Babesia bovis infections in cattle and B. canis infections in dogs are characterized by non-haemolytic anaemia and low parasitaemia during t he acute phase of the disease. In this phase of the disease, animals s uffer from hypotension followed by disturbances of the coagulation sys tem. This review discusses the hypothesis that may explain the process of parasite localization in the host, and, the consequences of such l ocalization. It is suggested that hypotension favours the interaction between infected erythrocytes and the endothelial lining, thus facilit ating localization of the infection. In addition, activation of the co agulation system by a parasite-derived molecule (one associated with t he surface of infected erythrocytes or a soluble antigen) might consol idate this situation by causing cellular plugs to form. The continued proliferation of parasites in such plugs may then result in the occurr ence of capillaries that are particularly heavily parasitised. An expl anation is also suggested for the protective effect of vaccines agains t clinical babesiosis, based on the soluble parasite antigens that are released into the medium in cultures of babesial parasites.