Rickettsial Infections among Ctenocephalides felis and Host Animals during a Flea-Borne Rickettsioses Outbreak in Orange County, California

Abstract

Due to a resurgence of flea-borne rickettsioses in Orange County, California, we investigated the etiologies of rickettsial infections of Ctenocephalides felis, the predominant fleas species obtained from opossums (Didelphis virginiana) and domestic cats (Felis catus), collected from case exposure sites and other areas in Orange County. In addition, we assessed the prevalence of IgG antibodies against spotted fever group (SFGR) and typhus group (TGR) rickettsiae in opossum sera. Of the 597 flea specimens collected from opossums and cats, 37.2% tested positive for Rickettsia. PCR and sequencing of rickettsial genes obtained from C. felis flea DNA preparations revealed the presence of R. typhi (1.3%), R. felis (28.0%) and R. felis-like organisms (7.5%). Sera from opossums contained TGR-specific (40.84%), but not SFGR-specific antibodies. The detection of R. felis and R. typhi in the C. felis fleas in Orange County highlights the potential risk for human infection with either of these pathogens, and underscores the need for further investigations incorporating specimens from humans, animal hosts, and invertebrate vectors in endemic areas. Such studies will be essential for establishing a link in the ongoing flea-borne rickettsioses outbreaks.

Fatal Flea-Borne Typhus in Texas: A Retrospective Case Series, 1985–2015

“…Because R. typhi and R. felis occur sympatrically in fleas in Texas, it is possible that R. felis may be responsible for some cases of flea-borne typhus36–38; however, vertebrates infected with R. felis characteristically produce antibodies that cross-react with antigens of spotted fever group rickettsiae rather than typhus group rickettsiae 39,40. Antibodies reactive with spotted fever group rickettsiae were detected in five of the patients in this series for whom these tests were performed, but each of these patients had corresponding typhus group titers that were at least 4-fold higher.…”

Direct evidence of <i>Rickettsia typhi</i> infection in <i>Rhipicephalus sanguineus</i> ticks and their canine hosts

“…This last alternate cycle was described during epidemic outbreaks of murine typhus, in communities from Texas and California that were not in touch with the classic transmission, however, data supported the infection of fleas by Rickettsia typhi but no rickettsemia in opossums, only anti-Rickettsia typhi antibodies. (Blanton et al, 2016;Maina et al, 2016). Other studies have demonstrated that dogs can play an important role in the transmission of murine typhus, as high antibody titers against Rickettsia typhi and rickettsemia have been demonstrated by IFA and PCR/sequencing in dog blood samples from different world regions including Yucatan; however, its potential as reservoirs remains to be assessed (Nogueras et al, 2013;Martinez-Ortiz et al, 2016).…”

Molecular Detection of Rickettsia felis in Haemaphysalis longicornis Ticks in Anhui Province of China

“…where R. felis is more prevalent in arthropods and mammals in the area than R. typhi [3,5,6,7]. In Asia, R. felis has been detected by PCR in fleas from hailand, South Korea, Afghanistan, Laos, Malaysia, and China), ticks from China and Japan, lice from China, mosquito from China, raccoons from Japan, dogs from China, cat from China and people from China and South Korea [8,9].…”