Histologic Features and Immunodetection of African Tick-bite Fever Eschar

摘要

African tick-bite fever (ATBF) is a rickettsiosis causedby Rickettsia africae. We describe histologic features andimmunodetection of R. africae in cutaneous inoculationeschars from 8 patients with ATBF, which was diagnosedby culture or association of positive PCR detection andpositive serologic results. We used quantitative imageanalysis to compare the pattern of inflammation of theseeschars with those from Mediterranean spotted fever. Weevaluated the diagnostic value of immunohistochemicaltechniques by using a monoclonal antibody to R. africae.ATBF eschars were histologically characterized by inflam-mation of vessels composed mainly of significantly morepolymorphonuclear leukocytes than are found in cases ofMediterranean spotted fever (p<0.05). Small amounts R.africae antigens were demonstrated by immunohistochem-ical examination in 6 of 8 patients with ATBF. Neutrophils inATBF are a notable component of the host reaction, per-haps because ATBF is a milder disease than the other rick-ettsioses. Immunohistochemical detection of rickettsialantigens may be useful in diagnosing ATBF