Table 2. Rickettsia rickettsii acquisition infestation 2 with Amblyomma aureolatum ticks on 4 guinea pigs 30 days after acquisition infestation 1, Brazil*.

Guinea pig	Temperature range, °C	IFA endpoint titer at day 0†	Feeding chamber‡	PCR on ticks after molting, no. infected/no. tested (% infected)
				Unfed nymphs	Unfed adults
1	No fever to 38.8	32,768	UL + IN	0/10 (0)	2/2 (100)
			UL	0/10 (0)
2	No fever to 38.4	32,768	UL + IN	0/10 (0)	3/3 (100)
			UL	0/10 (0)
3	No fever to 39.1	32,768	UL	0/30 (0)
			UL + IN	10/30 (33)	3/3 (100)
4	No fever to 39.2	65,536	UL	0/30 (0)
			UL + IN	5/30 (17)	3/3 (100)

*Each guinea pig was infested on day 0 with R. rickettsii IN and on day 3 with UL. Recovered engorged larvae and nymphs were allowed to molt to nymphs and adult ticks, respectively, which were tested by real-time PCR for presence of rickettsial DNA. dpi, days postinfestation; IFA, immunofluorescence assay; IN, infected nymphs; UL, uninfected larvae.
†Blood was collected at day 0 (30 days after acquisition infestation 1) and tested by IFA with R. rickettsii antigens.
‡Tick infestations were performed on 2 feeding chambers glued to the shaved back of each guinea pig, 1 chamber receiving IN and UL, the other receiving only UL (Figure).