Domestic dogs are mammalian reservoirs for the emerging zoonosis flea-borne spotted fever, caused by Rickettsia felis

Abstract

Rickettsia felis is an obligate intracellular bacterium that is being increasingly recognized as an etiological agent of human rickettsial disease globally. The agent is transmitted through the bite of an infected vector, the cat flea, Ctenocephalides felis, however there is to date, no consensus on the pathogen's vertebrate reservoir, required for the maintenance of this agent in nature. This study for the first time, demonstrates the role of the domestic dog (Canis familiaris) as a vertebrate reservoir of R. felis. The ability of dogs to sustain prolonged periods of rickettsemia, ability to remain asymptomatically infected with normal haematological parameters and ability to act as biological vehicles for the horizontal transmission of R. felis between infected and uninfected fleas provides indication of their status as a mammalian reservoir of this emerging zoonosis.

Figure 1

Flow diagrams showing the time lines of R. felis needle-inoculation experiment. The uncolored boxes indicate the beginning of experiment, the pink boxes report the initial IFAT, PCR and XTC-2 cell line culture results of the dogs and the light blue boxes report the PCR and XTC-2 cell line culture results of the fleas.

Figure 2

Flow diagrams showing the time lines of horizontal transmission of R. felis. The boxes in light blue indicate the horizontal transmission of R. felis via co-feeding fleas; the boxes in light pink indicate the horizontal transmission of R. felis via non-co-feeding fleas.

Figure 3

Graph showing the reciprocal IgG titers and PCR results for R. felis in blood of infected dogs by the days of post-infection. The shaded area represents seronegative titers of IFAT.

Figure 4

Graphs display the RBC, HGB, PLT and HCT of Dogs (A–G) during period of infection with R. felis. The shaded area represents the normal reference range for dogs.

Figure 5

Graph showing the WBC, LYM, MON and GRAN during period of infection with R. felis of Dogs (A–G). The shaded area represents the normal reference range for dogs.

Figure 6

Diagram showing the study dogs allocated for study.