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. 2006 Sep;12(9):1332-7.
doi: 10.3201/eid1209.051540.

Histologic features and immunodetection of African tick-bite fever eschar

Hubert Lepidi  1 , Pierre-Edouard Fournier, Didier Raoult
Affiliations

Histologic features and immunodetection of African tick-bite fever eschar

Hubert Lepidi et al. Emerg Infect Dis. 2006 Sep.

Abstract

African tick-bite fever (ATBF) is a rickettsiosis caused by Rickettsia africae. We describe histologic features and immunodetection of R. africae in cutaneous inoculation eschars from 8 patients with ATBF, which was diagnosed by culture or association of positive PCR detection and positive serologic results. We used quantitative image analysis to compare the pattern of inflammation of these eschars with those from Mediterranean spotted fever. We evaluated the diagnostic value of immunohistochemical techniques by using a monoclonal antibody to R. africae. ATBF eschars were histologically characterized by inflammation of vessels composed mainly of significantly more polymorphonuclear leukocytes than are found in cases of Mediterranean spotted fever (p < 0.05). Small amounts R. africae antigens were demonstrated by immunohistochemical examination in 6 of 8 patients with ATBF. Neutrophils in ATBF are a notable component of the host reaction, perhaps because ATBF is a milder disease than the other rickettsioses. Immunohistochemical detection of rickettsial antigens may be useful in diagnosing ATBF.

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Figures

Figure 1
Figure 1
Fibrinoid necrosis of a vessel in the dermis (arrow) with perivascular inflammatory infiltrates mainly composed of polymorphonuclear leukocytes (hematoxylin-eosin-saffron; original magnification ×250).
Figure 2
Figure 2
Coagulative necrosis (*) of the dermis surrounding necrotic vessels (arrow) (hematoxylin-eosin-saffron; original magnification ×250).
Figure 3
Figure 3
Inoculation eschar from a patient with African tick-bite fever showing numerous dermal inflammatory infiltrates mainly composed of polymorphonuclear leukocytes (immunoperoxidase staining with an anti-CD15 antibody; original magnification ×100).
Figure 4
Figure 4
Quantification of inflammatory changes in inoculation eschars from patients with African tick-bite fever (Rickettsia africae, n = 8) and patients with Mediterranean spotted fever (R. conorii, n = 15). Surface areas expressing CD15, CD68, CD3, CD20, and Factor VIII were quantified after immunostaining. Quantification of each parameter was evaluated by computer-assisted analysis of digitized microscopic images. Results were normalized and expressed as a percentage of the total skin tissue surface area. Columns represent mean values ± standard error.
Figure 5
Figure 5
Immunohistochemical detection of Rickettsia africae in the inoculation eschar of a patient with African tick-bite fever. Note the location of the bacteria in the endothelial and inflammatory cells of a blood vessel in the dermis (arrow) (monoclonal rabbit anti-R. africae antibody used at a dilution of 1:1,000 and hematoxylin counterstain; original magnification ×250).
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References

    1. Raoult D, Fournier PE, Fenollar F, Jensenius M, Prioe T, de Pina JJ, et al. Rickettsia africae, a tick-borne pathogen in travelers to sub-Saharan Africa. N Engl J Med. 2001;344:1504–10. 10.1056/NEJM200105173442003 - DOI - PubMed
    1. Kelly P, Matthewman L, Beati L, Raoult D, Mason A, Dreary M, et al. African tick-bite fever: a new spotted fever group rickettsiosis under an old name. Lancet. 1992;340:982–3. 10.1016/0140-6736(92)92878-J - DOI - PubMed
    1. Kelly PJ, Beati L, Matthewman LA, Mason PR, Dasch GA, Raoult D. A new pathogenic spotted fever group rickettsia from Africa. J Trop Med Hyg. 1994;97:129–37. - PubMed
    1. Kelly PJ, Beati L, Mason PR, Matthewman LA, Roux V, Raoult D. Rickettsia africae sp. nov., the etiological agent of African tick bite fever. Int J Syst Bacteriol. 1996;46:611–4. 10.1099/00207713-46-2-611 - DOI - PubMed
    1. Jensenius M, Fournier PE, Kelly P, Myrvang B, Raoult D. African tick bite fever. Lancet Infect Dis. 2003;3:557–64. 10.1016/S1473-3099(03)00739-4 - DOI - PubMed

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