Isolation and Identification ofRickettsia massiliaefromRhipicephalus sanguineusTicks Collected in Arizona

Abstract

Twenty Rhipicephalus sanguineus ticks collected in eastern Arizona were tested by PCR assay to establish their infection rate with spotted fever group rickettsiae. With a nested PCR assay which detects a fragment of the Rickettsia genus-specific 17-kDa antigen gene (htrA), five ticks (25%) were found to contain rickettsial DNA. One rickettsial isolate was obtained from these ticks by inoculating a suspension of a triturated tick into monolayers of Vero E6 monkey kidney cells and XTC-2 clawed toad cells, and its cell culture and genotypic characteristics were determined. Fragments of the 16S rRNA, GltA, rOmpA, rOmpB, and Sca4 genes had 100%, 100%, 99%, 99%, and 99%, respectively, nucleotide similarity to Rickettsia massiliae strain Bar29, previously isolated from R. sanguineus in Catalonia, Spain (L. Beati et al., J. Clin. Microbiol. 34:2688-2694, 1996). The new isolate, AZT80, does not elicit cytotoxic effects in Vero cells and causes a persistent infection in XTC-2 cells. The AZT80 strain is susceptible to doxycycline but resistant to rifampin and erythromycin. Whether R. massiliae AZT80 is pathogenic or infectious for dogs and humans or can cause seroconversion to spotted fever group antigens in the United States is unknown.

Rocky Mountain Spotted Fever in the United States, 2000–2007: Interpreting Contemporary Increases in Incidence

“…364D. [31][32][33][34][35][36][37][38] There is also evidence that Rickettsia amblyommii , a tick-borne spotted fever group Rickettsia previously considered nonpathogenic, may cause mild illness and be misdiagnosed as RMSF on common serologic assays. 39 Geographic variations in severity have been noted, and a focus of unusually mild illness has been noted in North Carolina where R. amblyommii is prevalent.…”

A Focus of Dogs and Rickettsia massiliae–Infected Rhipicephalus sanguineus in California

“…Our findings expand the known geographic range in North America for R. massiliae , which now includes southern California in addition to a reported focus in Arizona. 5 Numerous ticks containing R. massiliae were present on this property during 2008-2009. Canine infection with R. conorii (the etiologic agent of Mediterranean spotted fever) shows clinical symptoms and serum and hematologic abnormalities similar to those of Rocky Mountain spotted fever. 34 In both infections, rickettsiemia detectable between days 2 and 12 after inoculation develops in acutely ill dogs.…”

“…conorii (the etiologic agent of Mediterranean spotted fever) is not resistant. 4,5,23 The similar clinical manifestations, common vector within the area endemic for Mediterranean spotted fever, and primary use of cross-reactive serologic assays for diagnosis of rickettsial diseases complicate understanding the true prevalence and distribution of R. massiliae and associated human or potentially canine infections. A limited canine serosurvey in northeastern Spain demonstrated that 8.6-25% (n = 93) of Catalonian dogs were exposed to R. massiliae Bar29 and 4-20% to R. conorii or another cross-reacting Rickettsia .…”

Isolation of Rickettsia rhipicephali and Rickettsia bellii from Haemaphysalis juxtakochi Ticks in the State of São Paulo, Brazil

“…In addition, Rickettsia prowazekii (the agent of epidemic typhus) was reported in A. cajennense or Amblyomma imitator ticks in Mexico (28). Interestingly, all of these Rickettsia species (except for "Candidatus Rickettsia andeanae") have been isolated in the United States, from the same tick species and/or from tick species different from those in Latin America (12,23,28,34,45).…”