TABLE 4.

Artificial feeding of larvae and nymphs with three strains of spirochetes^a

Strain	No. positive for infection/total no. (%)
	Immersed larvaeb		Capillary-fed nymphsc
			1-day hold		3-day hold
	1 wk	3 wk	1 wk	3 wk	1 wk
B31-A3	12/15 (80)	9/15 (60)	23/23 (100)	21/22 (95.5)	23/28 (82.1)
A3-pB	3/11 (27.3)*	1/10 (10)*	3/26 (11.5)*	2/25 (8)*	0/21 (0)*
A3-pB22	10/14 (71.4)	4/13 (30.8)	13/24 (54.2)*	14/21 (67.7)*	2/34 (5.9)*

^a*, infection rate was significantly different than the infection rate of ticks that fed on B31-A3-injected mice for each column (P < 0.05, Fisher's exact test).

^bImmersed larvae were tested for infection at 1 and 3 wk after placement on mice. Of the mice fed on by B31-A3-infected, A3-pB-infected, or A3-pB22-infected larvae, respectively, one of one, zero of one, and one of one tested positive for infection.

^cNymphs were held for 1 or 3 days after capillary feeding before placement on mice and then tested for infection 1 and 3 wk after placement on mice. Of the mice fed on by B31-A3-infected, A3-pB-infected, or A3-pB22-infected nymphs held for 1 day, two of two, zero of two, and one of two mice, respectively, tested positive for infection.