Virulence of the Lyme disease spirochete before and after the tick bloodmeal: a quantitative assessment

Parasites & Vectors

Table 1 Infectious dose in mice of WTB. burgdorferi derived from unfed and fed ticks

Spirochete source		Mouse infection
	Inoculum^a (spirochetes/mouse)	Sero-positive mice^b (infected/no. inoculated)	Tissue isolation^c (infected/no. inoculated)
UNFED Ticks^d
Nymphs (group 1)	~1	0/5	0/5
	8	0/5	0/5
	80	0/5	0/5
Nymphs (group 2)	~10	0/5	0/5
	110	0/5	0/5
	1,100	0/5	0/5
	11,000	1/5	1/5
Adults	~1	0/5	0/5
	13	0/5	0/5
	130	0/5	0/5
	1,300	0/5	0/5
FED Ticks^e
Nymphs	~9	0/2	0/2
	90	5/5	5/5
	900	5/5	5/5
	9,000	5/5	5/5
	90,000	5/5	5/5

^aNo. of B. burgdorferi estimated by plating an aliquot of inocula for CFU
^bMice were bled 3 weeks after inoculation and assessed for seroconversion to B. burgdorferi whole cell lysates by immunoblot analysis
^cMice were euthanized 5 - 6 weeks after inoculation and infection determined by isolation of spirochetes from the ear, joint, and bladder tissues
^dGroups of unfed nymphs were homogenized in medium and serially diluted for inoculation into mice (nymph groups (1) and (2) represent pools of 10 and 30 ticks, respectively)
^eA group of 10 nymphs fed to repletion was homogenized in medium 7 days after drop-off and serially diluted for inoculation into mice

ISSN: 1756-3305