Babesiosis is a potentially severe, and sometimes rapidly fatal, tick-borne illness caused by a malaria-like protozoan, Babesia microti, that infects and destroys the red blood cells. The blacklegged tick appears to be the primary vector of this disease to humans. Ticks become infected with the protozoan by feeding on an infected animal known as a reservoir host. Reservoir hosts carry babesiosis parasites in their bloodstream for extended periods, so that ticks feeding on them may become infected. When the infected tick then feeds on its next host, babesiosis parasites are passed on to that host and the cycle of infection continues. Rodents, especially the white-footed mouse and meadow vole, are the reservoir hosts for B. microti in New Jersey.