Use of quantitative PCR to measure density of Borrelia burgdorferi in the midgut and salivary glands of feeding tick vectors

Quantitative real-time PCR was used to assay spirochetes in feeding ticks. Spirochetes in tick midguts increased sixfold, from 998 per tick before att achment to 5,884 at 48 h of attachment. Spirochetes in tick salivary glands increased > 17-fold, from 1.2 per salivary gland pair before feeding to 20 .8 at 72 h postattachment. The period of the most rapid increase in the num ber of spirochetes in the salivary glands occurred from 48 to 60 h postatta chment; this time period coincides with the maximal increase in transmissio n risk during nymphal tick feeding.