[The presence of Borrelia in the intestines and salivary glands of spontaneously infected adult Ixodes persulcatus Schulze ticks during bloodsucking].

A direct microscopic analysis of fixed smears and live preparations was used to reveal whether spirochetes are present in the gut and salivary glands of adult Ixodes persulcatus ticks spontaneously infected with Borrelia garinii and B. afzelii. Unfed ticks collected from a vegetation, partially fed ticks removed from human bodies, and ticks deliberately fed on laboratory animals were studied. In each preparation, all spirochetes were counted in 250 microscopic fields, and their concentration per 100 microscopic fields was determined. A total of 1962 ticks were individually analysed. The methods used on the study allowed a reliable identification of Borrelia in the viscera of not only unfed, but also of partially fed ticks. The infection rate in ticks that started bloodsucking was slightly lower than in the unfed ticks. This was associated with the decreased spirochete concentration in the preparations made from the partially fed ticks. Borrelia were frequently found in the salivary glands of the unfed infected I. persulcatus. During the first two to three days of bloodsucking, neither the proportion of ticks with spirochetes in the salivary glands, nor the spirochete concentrations increase. Borrelia migration from the tick gut into the salivary glands during early bloodsucking is not a prerequisite for or even important for pathogen transmission with saliva. The transmission rate appears to depend on the baseline proportion of the unfed ticks carrying spirochetes in their salivary glands.(ABSTRACT TRUNCATED AT 250 WORDS)