Human Infection withRickettsia felis,Kenya

To determine the cause of acute febrile illnesses other than malaria in the North Eastern Province, Kenya, we investigated rickettsial infection among patients from Garissa Provincial Hospital for 23 months during 2006-2008. Nucleic acid preparations of serum from 6 (3.7%) of 163 patients were positive for rickettsial DNA as determined by a genusspecifi c quantitative real-time PCR and were subsequently confi rmed by molecular sequencing to be positive for Rickettsia felis. The 6 febrile patients' symptoms included headache; nausea; and muscle, back, and joint pain. None of the patients had a skin rash. R ickettsial diseases are found worldwide and are caused by infection with obligate intracellular rickettsiae, which are transmitted to humans by arthropod vectors (e.g., lice, fl eas, ticks, and mites). Rickettsiae are associated with arthropods for a least a part of their life cycle and are passed to other arthropods by transovarial transmission or horizontal transmission involving vertebrate hosts (1). Rickettsiae are small, gram-negative, fastidious bacteria of the subdivision of Proteobacteria, which are frequently divided into 2 groups based on antigenicity, G+C content, culture conditions, and actin polymerization: 1) the typhus group including Rickettsia prowazekii and R. typhi, the causative agents of louse-borne epidemic and fl ea-borne murine typhus, and 2) the spotted fever group including >20 species that may cause tick-, fl ea-, and mite-borne rickettsioses (2). Infection of humans by rickettsiae often begins at the site of the bite of the arthropod vector and subsequently spreads through the draining lymph nodes throughout the body, resulting in infection of endothelial cells, which can lead to multiorgan pathologic changes associated with potentially life-threatening diseases (1).