Spotted Fever Rickettsiae in Ticks from the Northern Sinai Governate, Egypt

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  • Office of Tropical Medicine and International Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Ain Shams University, Research and Training Center on Vectors of Diseases, Virology Unit, Ben Gurion University of the Negev, Department of Microbiology and Immunology, School of Medicine, University of Maryland, Bethesda, Maryland, Egypt
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A field study was initiated in 1988 to investigate whether spotted fever group rickettsiae occur in geographic areas in Egypt that are adjacent to an area in the southern Israeli Negev that has a defined focus of spotted fever disease. Ticks were collected from dogs, sheep, and camels at four study sites in the northern Sinai. Tick hemolymph was processed for rickettsial detection by staining with fluorescein isothiocyanate-conjugated antibody to Rickettsia rickettsii. Of the 442 hemolymphs examined, 15 contained immunofluorescent rickettsiae. Eight hemolymph test-positive (HT +) ticks were Rhipicephalus sanguineus removed from dogs; the other HT + ticks comprised three Hyalomma species, H. anatolicum, H. impeltatum, and H. dromedarii. Both HT + and HT - ticks were tested for rickettsial DNA using the polymerase chain reaction (PCR). Eight of 10 HT + field-collected ticks were PCR positive (PCR +). All laboratory colony R. rickettsii-infected ticks were PCR +. No HT - ticks from field or laboratory isolates were PCR +.