Genome sequence of Rickettsia conorii subsp. indica, the agent of Indian tick typhus

The Molecular Detection of Bacterial Infections of Public Health Importance in Hard Tick (Ixodidae) Nymphs Collected from the Forest Fringes of Western Ghats in the Goa, Karnataka and Maharashtra States of India

A survey was conducted to determine the human tick-borne bacterial infections in the nymphs which were collected from Western Ghats' fringe forest areas. Tick nymphs were collected using the flagging method from the villages where cases Kyasanur Forest Disease (KFD) were previously reported in the states of Goa, Karnataka and Maharashtra. A total of 200 tick pools consisting of 4587 nymphs were tested by PCR for the detection of bacteria of public health importance, such as Coxiella burnetii and Rickettsia spp. Of these, four pools (4.8%) in Karnataka and three pools (4.4%) in Maharashtra were positive for Coxiella burnetii, while none of the samples from Goa state were positive. Rickettsia spp. were positively obtained from Maharashtra (51.5%), Goa (35.42%) and Karnataka (26.19%). The sequence results of Rickettsia spp. showed similarity to the spotted fever group Candidatus Rickettsia shennongii, Rickettsia conorii subsp. heilongjiangensis and Rickettsia spp. strain koreansis. Individuals are entering into the forest areas for various reasons are more likely to infect with Coxiella burnetii. and Rickettsia spp.

Natural Mediterranean Spotted Fever Foci, Qingdao, China

We sequenced DNA from spleens of rodents captured in rural areas of Qingdao, East China, during 2013-2015. We found 1 Apodemus agrarius mouse infected with Rickettsia conorii, indicating a natural Mediterranean spotted fever foci exists in East China and that the range of R. conorii could be expanding.

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.

Distribution and Ecological Drivers of Spotted Fever Group Rickettsia in Asia

Spotted fever group and related rickettsia (SFGR) are a neglected group of pathogens that belong to the genus Rickettsia. SFGR are zoonotic and are transmitted by arthropod vectors, primarily ticks, fleas and mites to accidental hosts. These emerging and re-emerging infections are widely distributed throughout the world. Land-use change and increasing human-wildlife conflict compound the risk of SFGR infection to local people in endemic areas and travelers to these regions. In this article, we discuss the rickettsial organisms causing spotted fever and related diseases, their arthropod vectors in Asia and the impact of land-use change on their spread.

Rickettsia Species Isolated from Dermacentor occidentalis (Acari: Ixodidae) from California

The Pacific Coast tick (Dermacentor occidentalis Marx, 1892) is one of the most widely distributed and frequently encountered tick species in California. This tick is the primary vector of an unclassified spotted fever group rickettsial pathogen, designated currently as Rickettsia 364D, the etiologic agent of a recently recognized tick-borne rickettsiosis known as Pacific Coast tick fever. Despite intensified interest in this pathogen, important questions remain regarding its taxonomic status and possible variations in genotype among different strains that could influence its pathogenicity. Only the extensively passaged prototypical isolate (strain 364-D) is widely available to rickettsiologists and public health scientists worldwide. To achieve a larger, more geographically diverse, and contemporary collection of strains, 1,060 questing adult D. occidentalis ticks were collected from 18 sites across six counties in northern and southern California in 2016 and 2017. Fourteen ticks (1.3%) yielded DNA of Rickettsia 364D and from these, 10 unique isolates from Lake and Orange counties were obtained. Additionally, Rickettsia rhipicephali was detected in 108 (10.2%) ticks, from which eight isolates were obtained, and Rickettsia bellii in six (0.6%), from which three isolates were obtained. The panel of recently acquired, low-passage strains of Rickettsia 364D derived from this study could enhance opportunities for investigators to accurately determine the taxonomic standing of this agent and to develop specific diagnostic assays for detecting infections with Rickettsia 364D in ticks and humans.

Indian tick typhus presenting as Purpura fulminans

Seriously ill patients presenting with purpura fulminans, sepsis and multi-organ failure often require extensive diagnostic workup for proper diagnosis and management. Host of common infections prevalent in the tropics, e.g. malaria, dengue; other septicemic infections e.g. meningococcemia, typhoid, leptospirosis, toxic shock syndrome, scarlet fever, viral exanthems like measles, infectious mononucleosis, collagen vascular diseases (Kawasaki disease, other vasculitis) diseases, and adverse drug reactions are often kept in mind, and the index of suspicion for rickettsial illness is quite low. We present a case of Indian tick typhus presenting with purpura fulminans (retiform purpura all over the body), sepsis and multiorgan failure without lymphadenopathy and eschar, successfully treated with doxycycline and discharged home. Hence, a high index clinical suspicion and prompt administration of a simple therapy has led to successful recovery of the patient.

Update on tick-borne rickettsioses around the world: a geographic approach

Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These zoonoses are among the oldest known vector-borne diseases. However, in the past 25 years, the scope and importance of the recognized tick-associated rickettsial pathogens have increased dramatically, making this complex of diseases an ideal paradigm for the understanding of emerging and reemerging infections. Several species of tick-borne rickettsiae that were considered nonpathogenic for decades are now associated with human infections, and novel Rickettsia species of undetermined pathogenicity continue to be detected in or isolated from ticks around the world. This remarkable expansion of information has been driven largely by the use of molecular techniques that have facilitated the identification of novel and previously recognized rickettsiae in ticks. New approaches, such as swabbing of eschars to obtain material to be tested by PCR, have emerged in recent years and have played a role in describing emerging tick-borne rickettsioses. Here, we present the current knowledge on tick-borne rickettsiae and rickettsioses using a geographic approach toward the epidemiology of these diseases.

Genome sequence of Rickettsia conorii subsp. israelensis, the agent of Israeli spotted fever

Rickettsia conorii subsp. israelensis is the agent of Israeli spotted fever. The present study reports the draft genome of Rickettsia conorii subsp. israelensis strain ISTT CDC1, isolated from a Rhipicephalus sanguineus tick collected in Israel.

Genome sequence of Rickettsia conorii subsp. caspia, the agent of Astrakhan fever

Rickettsia conorii subsp. caspia is the agent of Astrakhan fever, a spotted fever group rickettsiosis endemic to Astrakhan, Russia. The present study reports the draft genome of Rickettsia conorii subsp. caspia strain A-167.

Genome sequences published outside of Standards in Genomic Sciences, May-June 2012

The purpose of this table is to provide the community with a citable record of publications of ongoing genome sequencing projects that have led to a publication in the scientific literature. While our goal is to make the list complete, there is no guarantee that we may have omitted one or more publications appearing in this time frame. Readers and authors who wish to have publications added to subsequent versions of this list are invited to provide the bibliographic data for such references to the SIGS editorial office.

Cross-protection among Rickettsia species and subspecies in a guinea pig model of cutaneous infection

Pathogenic rickettsiae of the spotted fever group (SFG) induce skin lesions called "eschars" at the sites of arthropod bites. We recently described a guinea pig model based on eschar formation to predict the eventual pathogenicity of new Rickettsia species, and in this study, we used the model to study cross-protection among SFG Rickettsia species and subspecies. We showed that the intradermal inoculation of guinea pigs with Rickettsia conorii subsp. conorii significantly reduced, but not completely prevented, the number of eschars after sub-challenges with the same pathogen (P=0.0004). The same effect was also observed for other subspecies of the R. conorii complex. Additionally, the bacterial load in the eschars was significantly lower in immunized animals than in naïve animals. No protection was observed when sub-challenges were performed with other Rickettsia species, such as R. africae, R. sibirica subsp. mongolitimonae, R. aeschlimannii and R. massiliae. Our data suggest that patients may experience several episodes of infection with related or with the same species of Rickettsia. Moreover, the absence of cross-protection between Rickettsia species may explain the co-existence of two or more tick-borne rickettsioses in the same geographic areas.