Rickettsia typhi (prevalence 1.9%) and R. felis (prevalence 24.8%) DNA were detected in rat fl eas (Xenopsylla cheopis) collected from mice on Oahu Island, Hawaii. The low prevalence of R. typhi on Oahu suggests that R. felis may be a more common cause of rickettsiosis than R. typhi in Hawaii.M urine typhus is a febrile zoonotic disease caused by Rickettsia typhi. The classic view is that R. typhi circulates among rats (Rattus rattus or R. norvegicus) and rat fl eas (Xenopsylla cheopis) (1,2), although other rodents and their ectoparasites have been implicated in maintenance of R. typhi in nature. Humans become infected when they visit disease-endemic areas infested with rats and acquire infection by inhalation or by self-inoculating infected fl eas or fl ea feces into skin.The most recent outbreak of murine typhus in Hawaii occurred in 2002 with 47 cases reported on 5 islands (3). Concomitantly, an increase occurred in the mouse population on the island of Maui, which reported 35 human cases. Peak occurrence of murine typhus in Hawaii was in 1944 with 186 cases reported, of which 80% occurred on the island of Oahu (4). Previous serologic surveys in Hawaii have identifi ed antibodies reactive with R. typhi antigen in the Polynesian rat (R. exulans), black rat (R. rattus), Norway rat (R. norvegicus), and house mouse (Mus musculus) (3,4). The Indian mongoose (Herpestes auropunctatus) was also identifi ed as a potential reservoir; however, its role has not yet been evaluated. We conducted a molecular survey of fl eas in Oahu to characterize the prevalence and identity of rickettsiae in Hawaii.
The StudyM. musculus mice were collected during rodent population studies in the leeward and southeast parts of Oahu during the summers of 2004, and 2007. Fleas were combed from each animal, identifi ed as X. cheopis by using standard taxonomic keys, and kept frozen at -70°C until they were sent to the Centers for Disease Control and Prevention (Atlanta, GA, USA) for further analyses. Mice were humanely killed; only brains were removed and frozen.DNA was isolated from each fl ea by using the Biomek 2000 Laboratory Automation workstation (Beckman, Fullerton, CA, USA) and reagents from the Wizard Prep kit (Promega, Madison, WI, USA) (5). DNA from 20 mg of mouse brain tissue was isolated by using the QiaAmp Mini kit (QIAGEN, Valencia, CA, USA).