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Pathologic study of mice infected with Rickettsia tsutsugamushi R19 strain
1Department of Pathology, College of Medicine, Inha University, Inchon, Korea.
Abstract:
Scrub typhus, an acute febrile infectious disease caused by R. tsutsugamushi, has been reported from various parts of the far east and pacific rim of Asia including Korea. It is well known that all human pathogenic rickettsia share an affinity to endothelial cells of the small blood vessels and evoke vascular inflammation variably associated with a rash, microthrombi, and hemorrhage. We infected the ICR mice by inoculating sublethal doses of R. tsutsugamushi R19 strain intraperitoneally and observed the pathologic changes by time sequence. The histopathologic features of experimentally induced scrub typhus in the mice were generally nonspecific interstitial inflammations characterized by interstitial pneumonitis, periportal inflammation, multifocal hepatic necrosis, interstitial nephritis, sinusoidal engorgement, and lymphohistiocytic cell infiltration in lymph nodes and spleen. Contrary to the general features of other rickettsial diseases, the pathologic process of scrub typhus experimentally induced by R. tsutsugamushi R19 strain mainly involved the interstitial connective tissue but not the blood vessels.
Insights
Scrub typhus, caused by Orientia tsutsugamushi, primarily affects interstitial connective tissue, unlike other rickettsial diseases. This study details its pathological changes in mice, highlighting interstitial inflammation.
Area of Science:
- Pathology
- Infectious Diseases
- Microbiology
Background:
- Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi.
- Rickettsial diseases typically affect endothelial cells, causing vascular inflammation.
- Scrub typhus is prevalent in the Far East, including Korea.
Purpose of the Study:
- To investigate the histopathological changes of scrub typhus in a mouse model.
- To compare the pathology of scrub typhus with other rickettsial diseases.
Main Methods:
- ICR mice were inoculated with sublethal doses of Orientia tsutsugamushi R19 strain.
- Pathologic changes were observed sequentially through histopathology.
Main Results:
- Experimentally induced scrub typhus showed nonspecific interstitial inflammation.
- Key features included interstitial pneumonitis, periportal inflammation, hepatic necrosis, nephritis, and lymphoid infiltration.
- Unlike other rickettsial diseases, the pathology primarily involved interstitial connective tissue, not blood vessels.
Conclusions:
- The pathology of scrub typhus induced by O. tsutsugamushi R19 strain in mice is characterized by interstitial inflammation.
- This differs from the typical vascular pathology seen in other rickettsial infections.