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Susceptibility of inbred mice to Rickettsia parkeri
Britton J Grasperge1, Kathryn E Reif, Timothy D Morgan
1Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
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.
Insights
Rickettsia parkeri causes American boutonneuse fever. C3H/HeJ mice showed significant infection signs, including edema and splenomegaly, making them a potential model for studying this emerging tick-borne disease.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Veterinary Pathology
Background:
- Rickettsia parkeri is the agent of American boutonneuse fever.
- Limited data exists on R. parkeri host infection and pathology.
- Emerging tick-borne diseases necessitate robust animal models.
Purpose of the Study:
- To characterize R. parkeri infection in different mouse strains.
- To identify a suitable mouse model for R. parkeri transmission studies.
- To understand the pathology of R. parkeri rickettsiosis.
Main Methods:
- Inoculation of four inbred mouse strains (A/J, BALB/c, C3H/HeJ, C3H/HeN) with R. parkeri.
- Intravenous and intradermal inoculation routes were used.
- Assessment of infection, gross pathology, histopathology, and rickettsial load via qPCR.
Main Results:
- C3H/HeJ mice exhibited facial edema, splenomegaly, and characteristic eschar lesions.
- C3H/HeJ mice showed the highest rickettsial DNA concentrations in multiple organs.
- Other mouse strains (A/J, BALB/c, C3H/HeN) did not display consistent infection pathology.
Conclusions:
- C3H/HeJ mice are a promising model for R. parkeri infection studies.
- This model can facilitate research into tick transmission, dissemination, and pathology.
- Further studies are warranted to fully elucidate R. parkeri rickettsiosis.
