Infection status of bank vole offspring.

A bank vole offspring was considered to have been successfully challenged with B. afzelii if at least one engorged B. afzelii-infected nymph was collected and/or if it developed a systemic infection following the infectious tick challenge. A bank vole was defined as having a systemic infection with B. afzelii if it tested positive for more than one of the following six offspring infection criteria: (i) the presence of B. afzelii-specific IgG antibodies at 35 days p.i., (ii) the presence of B. afzelii in the ear tissue biopsy specimen at 35 days p.i., (iii) the presence of B. afzelii in the bladder at 70 days p.i., (iv) the presence of B. afzelii in the left ear at 70 days p.i., (v) the presence of B. afzelii in the left rear joint at 70 days p.i., and (vi) the presence in culture of live spirochetes from dissected organs at 70 days p.i. Note that 35 days p.i. and 70 days p.i. correspond to 70 days postbirth (PB) and 105 days PB, respectively.