title: Susceptibility of inbred mice to Rickettsia parkeri.
abstract: Rickettsia parkeri, a member of the spotted fever group Rickettsia, is the causative agent of American boutonneuse fever in humans. Despite the increased recognition of human cases, limited information is available regarding the infection of invertebrate and vertebrate hosts for this emerging tick-borne disease. Toward the development of a viable transmission model and to further characterize the pathology associated with R. parkeri infection, inbred mouse strains (A/J, BALB/c, C3H/HeJ, and C3H/HeN) were intravenously and intradermally inoculated with 10(5) low-passage-number R. parkeri (Portsmouth strain), and infection, gross pathology, and histopathology were scored. Additionally, a quantitative real-time PCR (qPCR) was performed to estimate rickettsial load in heart, lung, spleen, and liver tissues of infected mice at 19 days postinoculation. Of the A/J, BALB/c, and C3H/HeN mice, none displayed universal pathology consistent with sustained infection. Compared to age-matched control mice, the intravenously inoculated C3H/HeJ mice exhibited marked facial edema and marked splenomegaly upon gross examination, while the intradermally inoculated mice developed characteristic eschar-like lesions. The C3H/HeJ mice also exhibited the greatest concentrations of rickettsial DNA from heart, lung, liver, and spleen samples when examined by qPCR. The similarity of the pathology of human disease and sustained infection suggests that the C3H/HeJ strain of mice is a promising candidate for subsequent experiments to examine the tick transmission, dissemination, and pathology of R. parkeri rickettsiosis.
authors.affiliation: Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
authors.forename: Britton J
authors.initials: BJ
authors.lastname: Grasperge
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Reif
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Morgan
authors.forename: Piyanate
authors.initials: P
authors.lastname: Sunyakumthorn
authors.forename: Joseph
authors.initials: J
authors.lastname: Bynog
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Paddock
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Macaluso
mesh_terms: D000818:Animals; D004269:DNA, Bacterial / Q000302:isolation & purification; D020022:Genetic Predisposition to Disease; D007249:Inflammation; D007958:Leukocyte Count; D007962:Leukocytes / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012281:Rickettsia / Q000145:classification*; D012282:Rickettsia Infections / Q000235:genetics* / Q000382:microbiology* / Q000473:pathology; D012867:Skin / Q000473:pathology; D013045:Species Specificity; D013997:Time Factors
chemical_list: D004269:DNA, Bacterial