High seroprevalence of antibodies against spotted fever and scrub typhus bacteria in patients with febrile Illness, Kenya

Abstract

Serum samples from patients in Kenya with febrile illnesses were screened for antibodies against bacteria that cause spotted fever, typhus, and scrub typhus. Seroprevalence was 10% for spotted fever group, <1% for typhus group, and 5% for scrub typhus group. Results should help clinicians expand their list of differential diagnoses for undifferentiated fevers.

Keywords: Kenya; Rickettsia; bacteria; rickettsial infections; scrub typhus; seroprevalence; spotted fever; typhus fever.

Figure 1

Distribution of titers to spotted fever (SFG) and scrub typhus (STG) groups in patients recruited in various surveillance hospitals. A) For SFG, Garissa District Hospital (GSA), in semiarid northeastern Kenya, had more patients with higher titers compared with Alupe District Hospital (ALH), on the Kenya-Uganda border; Marigat District Hospital (MGT), on the floor of the Rift Valley; Malindi District Hospital (MDH), on the Indian Ocean coast; Kisii District Hospital (KSI), in the Kisii highlands; and Kisumu District Hospital and Obama Children Hospital (KSM), on the Lake Victoria basin. B) For STG, MGT had the most patients with titers of 1:400 and 1:1,600 compared with ALH, MDH, KSI, and KSM.

Figure 2

Western blot analysis using the Orientia spp.–specific antigen (Otr47b). Twenty scrub typhus reactive serum samples at a titer ≥1:6,000 were used. Negative controls were serum samples that were reactive to spotted fever and typhus group antigens. The scrub typhus reactive serum samples recognized the Otr47b antigen (lanes 2 and 3), but the spotted fever group and typhus group reactive serum samples did not (data not shown). Lane 1 was probed with a positive control serum sample from an earlier scrub typhus outbreak study (5). M, molecular mass standard, kDa.