High prevalence of “Candidatus Rickettsia andeanae” and apparent exclusion of Rickettsia parkeri in adult Amblyomma maculatum (Acari: Ixodidae) from Kansas and Oklahoma

Abstract

Amblyomma maculatum (the Gulf Coast tick), an aggressive, human-biting, Nearctic and Neotropical tick, is the principal vector of Rickettsia parkeri in the United States. This pathogenic spotted fever group Rickettsia species has been identified in 8–52% of questing adult Gulf Coast ticks in the southeastern United States. To our knowledge, R. parkeri has not been reported previously from adult specimens of A. maculatum collected in Kansas or Oklahoma. A total of 216 adult A. maculatum ticks were collected from 18 counties in Kansas and Oklahoma during 2011–2014 and evaluated by molecular methods for evidence of infection with R. parkeri. No infections with this agent were identified; however, 47% of 94 ticks collected from Kansas and 73% of 122 ticks from Oklahoma were infected with “Candidatus Rickettsia andeanae” a spotted fever group Rickettsia species of undetermined pathogenicity. These preliminary data suggest that “Ca. R. andeanae” is well-adapted to survival in populations of A. maculatum in Kansas and Oklahoma, and that its ubiquity in Gulf Coast ticks in these states may effectively exclude R. parkeri from their shared arthropod host, which could diminish markedly or preclude entirely the occurrence of R. parkeri rickettsiosis in this region of the United States.

Expanding Range of Amblyomma americanum and Simultaneous Changes in the Epidemiology of Spotted Fever Group Rickettsiosis in the United States

“…46 In Kansas and Oklahoma, the Gulf Coast tick may not carry R. parkeri because of high prevalence of "Candidatus Rickettsia andeanae", an agent of unknown human pathogenicity. 48 In our results, the HR in Kansas and Oklahoma was lower than other parts of the Gulf Coast tick's range, suggesting that the Gulf Coast tick may not be a vector associated with severe SFG rickettsiosis in these states.…”

Amblyomma sculptum: genetic diversity and rickettsias in the Brazilian Cerrado biome

“…Otherwise, there is no knowledge concerning Ca. R. andeanae pathogenicity, although it may cause the decrease or exclusion of R. parkeri rickettsiosis (Paddock et al, 2015). This makes Ca.…”

Rickettsia parkeri and Candidatus Rickettsia andeanae in Amblyomma maculatum Group Ticks

“…Although R. parkeri in an engorged nymph was reported once in Oklahoma, R. parkeri has not been reported in adult A. maculatum ticks in Oklahoma or Kansas. To date, all test-positive adult ticks in Kansas and Oklahoma have been infected with Candidatus Rickettsia andeanae (2). The absence of R. parkeri in Oklahoma is surprising because it was detected in A. maculatum group ticks recovered from dogs in Arkansas counties bordering eastern Oklahoma (3) and in adult A. maculatum ticks in Texas (4), and A. maculatum ticks have been present in Oklahoma since the 1940s (4).…”

“…Candidatus R. andeanae prevalence in A. maculatum ticks varies inversely with R. parkeri prevalence in some regions (4). Although Candidatus R. andeanae is not known to cause human illness (4), the high prevalence of Candidatus R. andeanae in Oklahoma ticks might interfere with R. parkeri development, limiting its distribution (2). The potential presence of this human pathogen in the largest metropolitan area in the state, and 1 of the largest in the central United States, necessitates thorough case evaluation of future SFGR cases in this region.…”

“…The family Astroviridae comprises 2 genera, Mamastrovirus and Avastrovirus, and classification is based on host origin. Astroviruses cause diarrhea and neurologic diseases in mammals and a spectrum of diseases, including diarrhea, hepatitis, and nephritis, in birds (2). Astrovirus is associated with respiratory disease in humans, cattle, and pigs (3)(4)(5) and has also been found in fecal samples from roe deer with gastrointestinal illness in Denmark (6).…”