Urban Focus ofRickettsia typhiandRickettsia felisin Los Angeles, California

Abstract

Classic murine typhus, caused by Rickettsia typhi, is endemic in the continental United States in areas of Texas and southern California. We conducted an environmental investigation in an urban area of Los Angeles identified as the probable exposure site for a case of murine typhus. Four Rattus norvegicus heavily infested with Xenopsylla cheopis (average 32.5 fleas per animal, range 20-42) were trapped, and fleas, blood, and tissues were collected. DNAs from all specimens were tested for R. typhi and Rickettsia felis using a TaqMan assay targeting the rickettsial citrate synthase gene. Although rickettsiemia was not detected, DNA of R. felis was detected in at least one tissue from each rat. Tissues from 3 rats were also positive for R. typhi DNA. R. typhi and R. felis DNAs were detected in fleas collected from each animal with average minimal infection rates of 10% and 32.3%, respectively. Although R. typhi still circulates in urban Los Angeles in the classic Oriental flea-rat cycle, R. felis is more prevalent, even in this association.

An Investigation ofBartonellaspp.,Rickettsia typhi, and Seoul Hantavirus in Rats (Rattusspp.) from an Inner-City Neighborhood of Vancouver, Canada: Is Pathogen Presence a Reflection of Global and Local Rat Population Structure?

“…That being said, more than one Bartonella sp. was identified in that study (Gundi et al 2012), and R. typhi (Abramowicz et al 2011) has been found in rats from Los Angeles. Genetic characterization of global rat population structures may help to elucidate the distribution of RAZ among different cities.…”

“…Although spleen has been successfully used for detecting R. typhi infection in rats (Abramowicz et al 2011), the period of active rickettsemia detectable by PCR can be transient (i.e., < 1 month) (Azad 1990), and the bacterium can be maintained in fleas (the vectors for transmission) (Azad 1990, Azad andBeard 1998). For these reasons, negative PCR results alone cannot completely rule out the presence of circulating R. typhi.…”

“…Although these pathogens have been identified in number of different geographic locations (Arikawa et al 1994, Gundi et al 2004, Easterbrook et al 2007a, Heyman et al 2009, Hsieh et al 2010, Psaroulaki et al 2010, Abramowicz et al 2011, studies that specifically seek to quantify their prevalence in urban rat populations have occasionally found one or more of them to be absent (Yanagihara 1990, Ellis et al 1999, Cueto et al 2008, Inoue et al 2008, Jiang et al 2008, Eremeeva et al 2012. In many cases, it is unclear if the pathogen is truly absent, or if absence is a result of undersampling (Yanagihara.…”

Molecular Detection of Rickettsia felis in Different Flea Species from Caldas, Colombia

“…With a larger sample of X. cheopis and other flea species, it would be of interest to test for the presence of coinfection with R. felis and R. typhi in the same positive fleas, because it was previously reported in experimental works 42 and under natural conditions. 22,43,44 The analysis of the sequence electropherograms showed lack of ambiguity in the nucleotide assignments for all samples included. Because the PCR products were derived from pools in which several members could be positive, the clean sequence reads suggest that the amplified fragments were highly conserved and/or that only one flea in each pool was positive for a single Rickettsia.…”

High Prevalence of Rickettsia typhi and Bartonella Species in Rats and Fleas, Kisangani, Democratic Republic of the Congo

“…The prevalence of R. typhi in fleas and rodents DRC is one of the highest from the world. In the last years, R. typhi was identified in 10.8% of X. cheopis pools (4 of 16) in Indonesia, 33 in tissues from three rats and in 10% of fleas from each animal in California, 34 in 4% X. cheopis and 6.6% in Leptopsylla segnis in Cyprus, 35 and in 3.2% flea pools in Korea. 36 The flea remains infected with R. typhi for life with good fitness and the horizontal and vertical transmission increase the infected populations in this endemic area.…”