Isolation of a divergent strain of Rickettsia japonica from Dew's Australian bat Argasid ticks (Argas (Carios) dewae) in Victoria, Australia

Trends in Bacterial Pathogens of Bats: Global Distribution and Knowledge Gaps

Bats have received considerable recent attention for infectious disease research because of their potential to host and transmit viruses, including Ebola, Hendra, Nipah, and multiple coronaviruses. These pathogens are occasionally transmitted from bats to wildlife, livestock, and to humans, directly or through other bridging (intermediate) hosts. Due to their public health relevance, zoonotic viruses are a primary focus of research attention. In contrast, other emerging pathogens of bats, such as bacteria, are vastly understudied despite their ubiquity and diversity. Here, we describe the currently known host ranges and geographic distributional patterns of potentially zoonotic bacterial genera in bats, using published presence-absence data of pathogen occurrence. We identify apparent gaps in our understanding of the distribution of these pathogens on a global scale. The most frequently detected bacterial genera in bats are Bartonella, Leptospira, and Mycoplasma. However, a wide variety of other potentially zoonotic bacterial genera are also occasionally found in bats, such as Anaplasma, Brucella, Borrelia, Coxiella, Ehrlichia, Francisella, Neorickettsia, and Rickettsia. The bat families Phyllostomidae, Vespertilionidae, and Pteropodidae are most frequently reported as hosts of bacterial pathogens; however, the presence of at least one bacterial genus was confirmed in all 15 bat families tested. On a spatial scale, molecular diagnostics of samples from 58 countries and four overseas departments and island states (French Guiana, Mayotte, New Caledonia, and Réunion Island) reported testing for at least one bacterial pathogen in bats. We also identified geographical areas that have been mostly neglected during bacterial pathogen research in bats, such as the Afrotropical region and Southern Asia. Current knowledge on the distribution of potentially zoonotic bacterial genera in bats is strongly biased by research effort towards certain taxonomic groups and geographic regions. Identifying these biases can guide future surveillance efforts, contributing to a better understanding of the ecoepidemiology of zoonotic pathogens in bats.

Detection of Rickettsia lusitaniae Among Ornithodoros sawaii Soft Ticks Collected From Japanese Murrelet Seabird Nest Material From Gugul Island, Republic of Korea

In a follow-up to the investigations of soft ticks identified from seabird nest soil and litter collected from coastal islands of the Republic of Korea (ROK), Ornithodoros sawaii and Ornithodoros capensis were assessed for the presence and identification of rickettsiae. Ticks collected from samples of 50-100 g of nest litter and soil from seabird nests were identified individually by morphological techniques, and species confirmed by sequencing of the mt-rrs gene. Subsequently, tick DNA preparations were screened for the presence of rickettsiae using a genus-specific nested PCR (nPCR) assay targeting the 17 kDa antigen gene. The amplicons from the 17 kDa assay and two additional nPCR assays targeting the gltA and ompB gene fragments were sequenced and used to identify the rickettsiae. A total of 134 soft ticks belonging to two species, O. sawaii Kitaoka & Suzuki 1973 (n = 125) and O. capensis Neumann 1901 (n = 9), were collected. Rickettsia lusitaniae DNA was detected and identified among O. sawaii ticks (n = 11, 8.8%) collected from nest litter and soil of the Japanese murrelet (Synthliboramphus wumizusume Temminck 1836) at Gugul Island along the western coastal area of the ROK. This study confirmed for the first time the presence of R. lusitaniae associated with O. sawaii collected from migratory seabird nests in the ROK.

Screening of tick-borne pathogens in argasid ticks in Zambia: Expansion of the geographic distribution of Rickettsia lusitaniae and Rickettsia hoogstraalii and detection of putative novel Anaplasma species

Ticks (Ixodidae and Argasidae) are important arthropod vectors of various pathogens that cause human and animal infectious diseases. Many previously published studies on tick-borne pathogens focused on those transmitted by ixodid ticks. Although there are increasing reports of viral pathogens associated with argasid ticks, information on bacterial pathogens they transmit is scarce. The aim of this molecular study was to detect and characterize Rickettsia and Anaplasmataceae in three different argasid tick species, Ornithodoros faini, Ornithodoros moubata, and Argas walkerae collected in Zambia. Rickettsia hoogstraalii and Rickettsia lusitaniae were detected in 77 % (77/100) of Ar. walkerae and 10 % (5/50) of O. faini, respectively. All O. moubata pool samples (n = 124) were negative for rickettsial infections. Anaplasmataceae were detected in 63 % (63/100) of Ar. walkerae and in 82.2 % (102/124) of O. moubata pools, but not in O. faini. Phylogenetic analysis based on the concatenated sequences of 16S rRNA and groEL genes revealed that Anaplasma spp. detected in the present study were distinct from previously validated Anaplasma species, indicating that the current knowledge on the diversity and vector range of Anaplasma spp. is incomplete. Our findings highlight new geographical records of R. lusitaniae and R. hoogstraalii and confirm that the wide geographic distribution of these species includes the African continent. The data presented here increase our knowledge on argasid tick-borne bacteria and contribute toward understanding their epidemiology.

Expansion of Tick-Borne Rickettsioses in the World

Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These infections are among the oldest known diseases transmitted by vectors. In the last three decades there has been a rapid increase in the recognition of this disease complex. This unusual expansion of information was mainly caused by the development of molecular diagnostic techniques that have facilitated the identification of new and previously recognized rickettsiae. A lot of currently known bacteria of the genus Rickettsia have been considered nonpathogenic for years, and moreover, many new species have been identified with unknown pathogenicity. The genus Rickettsia is distributed all over the world. Many Rickettsia species are present on several continents. The geographical distribution of rickettsiae is related to their vectors. New cases of rickettsioses and new locations, where the presence of these bacteria is recognized, are still being identified. The variety and rapid evolution of the distribution and density of ticks and diseases which they transmit shows us the scale of the problem. This review article presents a comparison of the current understanding of the geographic distribution of pathogenic Rickettsia species to that of the beginning of the century.

Cutaneous Immunoprofiles of Three Spotted Fever Group Rickettsia Cases

Spotted fever group rickettsia (SFGR) can cause mild to fatal illness. The early interaction between the host and rickettsia in skin is largely unknown, and the pathogenesis of severe rickettsiosis remains an important topic. A surveillance of SFGR infection by PCR of blood and skin biopsy specimens followed by sequencing and immunohistochemical (IHC) detection was performed on patients with a recent tick bite between 2013 and 2016. Humoral and cutaneous immunoprofiles were evaluated in different SFGR cases by serum cytokine and chemokine detection, skin IHC staining, and transcriptome sequencing (RNA-seq).

Spotted fever group rickettsia (SFGR) can cause mild to fatal illness. The early interaction between the host and rickettsia in skin is largely unknown, and the pathogenesis of severe rickettsiosis remains an important topic. A surveillance of SFGR infection by PCR of blood and skin biopsy specimens followed by sequencing and immunohistochemical (IHC) detection was performed on patients with a recent tick bite between 2013 and 2016. Humoral and cutaneous immunoprofiles were evaluated in different SFGR cases by serum cytokine and chemokine detection, skin IHC staining, and transcriptome sequencing (RNA-seq). A total of 111 SFGR cases were identified, including 79 “Candidatus Rickettsia tarasevichiae,” 22 Rickettsia raoultii, 8 Rickettsia sibirica, and 2 Rickettsia heilongjiangensis cases. The sensitivity to detect SFGR in skin biopsy specimens (9/24, 37.5%) was significantly higher than that in blood samples (105/2,671, 3.9%) (P < 0.05). As early as 1 day after the tick bite, rickettsiae could be detected in the skin. R. sibirica infection was more severe than “Ca. Rickettsia” and R. raoultii infections. Increased levels of serum interleukin-18 (IL-18), IP10, and monokine induced by gamma interferon (MIG) and decreased levels of IL-2 were observed in febrile patients infected with R. sibirica compared to those infected with “Ca. Rickettsia.” RNA-seq and IHC staining could not discriminate between SFGR-infected and uninfected tick bite skin lesions. However, the type I interferon (IFN) response was differently expressed between R. sibirica and R. raoultii infections at the cutaneous interface. It is concluded that skin biopsy specimens were more reliable for the detection of SFGR infection in human patients although the immunoprofile may be complicated by immunomodulators induced by the tick bite.

A relapsing fever Borrelia and spotted fever Rickettsia in ticks from an Andean valley, central Chile

In humans, emerging infectious diseases are mostly zoonoses with ticks playing an important role as vectors. Tick-borne relapsing fever Borrelia and spotted fever Rickettsia occur in endemic foci along tropical and subtropical regions of the globe. However, both are widely neglected etiologic agents. In this study, we performed molecular analyses in order to assess the presence of Borrelia and Rickettsia DNA in ticks infesting small-mammals within a National Reserve located in the Andes Mountains, central Chile. While hard ticks were negative for the presence of both agents, sequences of four rickettsial (gltA, htrA, ompA, ompB) and two borrelial (16S rRNA and flaB) genes were obtained from larvae of an Ornithodoros sp. morphologically related with Ornithodoros atacamensis. Phylogenetic analyses indicated that the detected Borrelia and Rickettsia spp. belong to the relapsing fever and spotted fever groups, respectively. Moreover, the agents formed monophyletic clades with Rickettsia amblyommatis and "Candidatus Borrelia johnsonii." As positive ticks parasitize rodents within a highly visited National Reserve where outdoor activities are of common practice, the risk for human parasitism should not be discarded.