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Volume 17, Number 5—May 2011

Experimental Infection of Amblyomma aureolatum Ticks with Rickettsia rickettsii

Marcelo B. LabrunaComments to Author , Maria Ogrzewalska, João F. Soares, Thiago F. Martins, Herbert S. Soares, Jonas Moraes-Filho, Fernanda A. Nieri-Bastos, Aliny P. Almeida, and Adriano Pinter
Author affiliations: Author affiliations: University of São Paulo, São Paulo, Brazil (M.B. Labruna, M. Ogrzewalska, J.F. Soares, T.F. Martins, H.S. Soares, J. Moraes-Filho, F.A. Nieri-Bastos, A.P. Almeida); Superintendency of Control of Endemic Diseases, São Paulo (A. Pinter)

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Table 1

Clinical data of hosts infested by a Rickettsia rickettsii–infected colony of Amblyomma aureolatum ticks, and results of PCR performed on unfed ticks from 4 consecutive generations (F1 to F4)*

Tick stage and generation Infested hosts
PCR of unfed ticks,
no. infected/no. tested
Host, no. No. ticks/host Fever†
No. deaths Diagnostic test
No. Onset, dpi PCR‡ IFA§
Nymph–F1 Guinea pig, 2 50 2 6 2 Pos ND 45/45¶
Adult–F1 Dog, 2 20 couples 0 0 ND ND 10/10
Larva–F2 Guinea pig, 2 1,000–2,000 2 7–8 1 ND Pos
Larva–F2 Rabbit, 3 1,000–2,000 3 7–9 0 ND Pos
Nymph–F2 Guinea pig, 3 80 3 5 2 Pos Pos 30/30
Nymph–F2 Rabbit, 1 200 1 6 0 ND Pos
Adult–F2 Rabbit, 2 7 couples 2 7–8 0 ND Pos
Larva–-F3 Guinea pig, 4 1,000–2,000 4 7–8 2 Pos Pos
Nymph–F3 Rabbit, 1 400 1 6 0 ND Pos
Adult–F3 Dog, 1 12 couples 0 0 ND ND
Larva–F4 Guinea pig, 5 1,000–3,000 5 6–7 1 ND Pos 100/100
Nymph–F4 Rabbit, 1 500 1 5 0 ND Pos 30/30

*dpi, days postinfestation; IFA, immunofluorescence assay; pos, positive; ND, not done; –, data not collected.
†Rectal temperature >40°C.
‡PCR performed on lung-extracted DNA from guinea pigs that died during the febrile period.
§A positive result means seroconversion, namely nonreactive (titer <64) at 0 DPI, and reactive (titer >1,024) at 21 dpi.
Previously reported by Labruna et al. (9).

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