Location and ultrastructure of spotted fever rickettsiae in nymphal Haemaphysalis hystricis ticks

The Haemaphysalis hystricis ticks we collected contained rod-shaped rickettsiae (length, 1.3μm; diameter, 0.3μm) in midgut epithelial cells, rectal sac cells, muscle cells surrounding trachea, cells of the central nervous system, and granular cells of the salivary glands. These microorganisms, which were defined as Rickettsia japonica by PCR analysis, existed freely in the cytoplasm of the cells and were surrounded by an electron-lucent (halo) zone. Nuclear localization and proliferation of the rickettsia were present in salivary gland cells. The rickettsial species we evaluated also demonstrate trans-stadial transmission because we used nymphal ticks, which molted from engorged larvae. This report is the first to describe the location and ultrastructure of spotted fever rickettsiae in H. hystricis ticks.