New Jersey-Wide Survey of Spotted Fever Group Rickettsia (Proteobacteria: Rickettsiaceae) in Dermacentor variabilis and Amblyomma americanum (Acari: Ixodida: Ixodidae)

Abstract

For the last decade, the New Jersey (NJ) Department of Health has reported between 42 and 144 new cases each year of "spotted fever group rickettsiosis" (SFGR), a statistic that reflects uncertainty regarding which rickettsial agents (Proteobacteria: Rickettsiaceae: Rickettsia) are infecting NJ residents. To identify the Rickettsia circulating in NJ ticks, we used a combination of conventional and real time PCR approaches to screen 560 Dermacentor variabilis Say and 245 Amblyomma americanum L. obtained from a 1-day statewide surveillance in May 2018 and an additional 394 D. variabilis collected across NJ in 2013-2018. We found zero D. variabilis infected with Rickettsia rickettsii, the agent of Rocky Mountain spotted fever and, on average, 1.3% infected with presumed nonpathogenic Rickettsia montanensis. We also found zero A. americanum infected with R. rickettsii, and 20% infected with Rickettsia amblyommatis, a prevalence somewhat lower than in more southern states. Overall, we conclude that it is unlikely that R. rickettsii vectored by D. variabilis is a primary cause of SFGR cases in NJ and discuss our findings in the context of known facts and current limitations. We conclude that understanding the causes of SFGR east of the Mississippi will require collaboration among medical doctors, public health authorities, and medical entomologists to follow up presumptive human cases of SFGR with detailed histories of exposure, species-specific molecular assays, and active surveillance of putative vectors and the pathogens they may carry.

Identification ofRickettsiaspp. andBabesia conradaeinDermacentorspp. Collected from Dogs and Cats Across the United States

“…Even though D. variabilis and D. andersoni are considered primary vectors of R. rickettsii , the causative agent of RMSF, we did not detect this pathogen in any Dermacentor tick ( n = 848) collected from dogs and cats in 44 U.S. states. Instead, we identified various other SFGR, which support data from other studies reporting a range of SFGR and a low prevalence of R. rickettsii in Dermacentor ticks (Moncayo et al 2010 , Fritzen et al 2011 , Trout Fryxell et al 2015 , Santanello et al 2018 , Dykstra et al 2020 , Francis et al 2020 , Luedtke et al 2020 , Occi et al 2020 ). In fact, when identified in D. variabilis , R. rickettsii has a reported prevalence less than 1%; however, this is in contrast to previous reports of greater than 8% of ticks harboring R. rickettsii (Schriefer and Azad 1994 , Stromdahl et al 2011 , Kakumanu et al 2018 , Hecht et al 2019 ).…”

Enabling metagenomic surveillance for bacterial tick-borne pathogens using nanopore sequencing with adaptive sampling

“…For example, human infectious A. phagocytophilum strains can be rapidly differentiated from non-human infectious ungulate strains without requiring nested PCR [45]. Genetically similar species, such as spotted fever group rickettsiae (some of which are not human infectious), will be rapidly differentiable in the field rather than relying on PCR amplification followed by sequencing or restriction fragment length polymorphism techniques, as is currently done [46,47].…”

Metagenomic analysis of human-biting cat fleas in urban northeastern United States of America reveals an emerging zoonotic pathogen

“…Fleas from six positive pools were individually tested with the same assay, revealing six positive individuals (5.6%) with a single positive per pool. We then amplified and sequenced fragments of the gltA 6 (Accession no. MT901296) and ompB 14 (Accession no.…”

“…Fleas from positive pools were individually tested with the same qPCR assay to pinpoint which fleas in each pool were positive. To identify the Rickettsia to species level we amplified and sequenced a 608 bp fragment of the rickettsia gltA gene using primers PgltA-2F 5′-TTCTCATCCTATGGCTATTATGC-3′ and PgltA-2R 5′-TTCAAGTTCTATTGCTATTTG-3′ 6 and a 820 bp fragment of the rickettsia ompB gene using primers 120-M59 and 120–807 14 . Positive and negative controls produced the expected results in all tests performed.…”

“…Species from all three groups are common in wild and domestic mammals globally; SFG transmission to humans occurs via tick bite, while many arthropods including fleas are known vectors of TG and TRG 4 . Since 2000, cases of presumptive SFG have increased markedly in the mid-Atlantic states, including New Jersey, associated with reduced morbidity and mortality 5 , a puzzling phenomenon since recent surveys of the primary tick vectors have seldomly detected the presence of SFG Rickettsia 6 .…”