Preliminary observations on ultrastructure of borreliae in tissues of Ixodes persulcatus

We observed Lyme borrelia by electron microscopy in the tissues of the ticks, Ixodes persulcatus, which were indicated positive for borreliae by BSK cultures of their internal organs. Borreliae (0.25 micron in diameter) were found only in the lumen of the midgut. They were closely associated with the microvilli on the midgut epithelium but never penetrated into the epithelial cells. Ultrastructural features common to Lyme borreliae., i.e., the three-layered membranes surrounding the cytoplasm and orientation of the flagella insertions, were obviously confirmed. The present results are useful to understand tick tissue-borrelia interface.