Rocky Mountain spotted fever. Gastrointestinal and pancreatic lesions and rickettsial infection.

Recent clinical studies have shown a high incidence of nausea, vomiting, diarrhea, and abdominal pain in Rocky Mountain spotted fever (RMSF), and case reports have documented rickettsial infection and vascular injury in the small intestine, appendix, and gallbladder. To determine the incidence and distribution of Rickettsia rickettsii and rickettsial lesions that might be the basis for these clinical manifestations of RMSF, tissues that were available from the stomach, small intestine, colon, and pancreas in fatal cases of RMSF were examined. Lesions were identified in pancreatic tissue in 91% of cases and in tissue obtained from the stomach, small intestine, and colon in all cases. Most tissues were judged to be only moderately injured. Organisms of R rickettsii were demonstrated by immunofluorescence in 14 (50%) of 28 cases and, when identified, correlated topographically with the location of vascular injury. These observations support the concept of rickettsial vascular injury of the gastrointestinal (GI) tract and pancreas leading to GI signs and symptoms in RMSF.