Table 1. Rickettsia rickettsii acquisition infestation 1 with Amblyomma aureolatum ticks on 6 guinea pigs, Brazil*.
| Guinea pig | Fever onset, dpi (maximum temperature, °C) | IFA endpoint titer at 21 dpi† | Feeding chamber‡ | PCR on ticks after molting, no. infected/no. tested (% infected) | |
|---|---|---|---|---|---|
| Unfed nymphs | Unfed adults | ||||
| 1 | 6 (40.3) | 65,536 | UL + IN | 10/10 (100) | 10/10 (100) |
|
|
|
|
UL |
10/10 (100) |
|
| 2 | 8 (40.0) | 65,536 | UL + IN | 9/9 (100) | 10/10 (100) |
|
|
|
|
UL |
10/10 (100) |
|
| 3 | 8 (40.5) | 8,192 | UL + IN | 15/15 (100) | 5/5 (100) |
|
|
|
|
UL |
15/15 (100) |
|
| 4 | 5 (40.7) | 65,536 | UL | 15/15 (100) | |
|
|
|
|
UL + IN |
15/15 (100) |
8/8 (100) |
| 5 | 9 (40.0) | 16,384 | UL | 15/15 (100) | |
|
|
|
|
UL + IN |
15/15 (100) |
8/8 (100) |
| 6 | 7 (40.4) | 16,384 | UL | 15/15 (100) | |
| UL + IN | 15/15 (100) | 6/6 (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 21 dpi 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).