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

[First autochthonous case of spotted fever associated with the Reserva Ecológica Costanera Sur, Buenos Aires City]

The first autochthonous case of rickettsiosis is reported here. The case occurred in the Costanera Sur Ecological Reserve, a protected area of the City of Buenos Aires, in August 2022, where 4 species of ticks were found, namely Amblyomma aureolatum, Ixodes auritulus sensu lato, Rhipicephalus sanguineus sensu stricto and Amblyomma triste. The epidemiological, ecological, clinical and laboratory aspects that allowed timely diagnosis and appropriate treatment are also described.

Molecular detection of rickettsial agents in Amblyomma maculatum ticks (Ixodida: Ixodidae) from Ecuador

Rickettsiales are obligate intracellular bacteria that need vertebrates and arthropods to maintain their life cycles. Some species of the genera Anaplasma, Ehrlichia, and Rickettsia are transmitted by ticks to both animals and humans and can cause mild to severe and even fatal cases. In the Americas, there is substantial data on rickettsial agents, encompassing both clinical cases and the detection of these agents in ticks, but in Ecuador, the information about them remains poorly understood. Therefore, the objective of this study was to detect molecularly rickettsial agents in Amblyomma maculatum ticks in both parasitic and free-living phases collected from domestic animals and pasture in five localities across three coastal provinces of Ecuador. Rickettsia parkeri, Candidatus Rickettsia andeanae, and Ehrlichia sp. were recorded in A. maculatum for the first time in Ecuador. These records were made in a region where antibodies to the Spotted Fever Rickettsia Group were detected in humans. Additional studies are needed to characterize Ehrlichia sp. at a specific level. Furthermore, recognizing the specific Rickettsiales species circulating in the ticks and the hosts within a region is crucial for assessing potential contact risks.

Serological and Molecular Survey of Rickettsial Agents in Wild Boars (Sus scrofa) from Midwestern Brazil

Wild boars (Sus scrofa L.) are considered among the most harmful invasive species worldwide, causing irreversible ecosystem damage, acting as zoonotic spreaders and reservoirs, threatening human and animal health, and having an important economic impact. Accordingly, the present study has assessed the rickettsial exposure, tick infestation of wild boars, and rickettsial DNA presence in ticks from infested animals from the Cerrado biome in midwestern Brazil. Anti-Rickettsia spp. antibodies were detected in serum samples of wild boars by immunofluorescence assay. Overall, 106/285 (37.2%) wild boar serum samples from 13 to 18 (72.2%) municipalities showed seroreactivity to at least one of the four Rickettsia spp. antigens tested, the largest number of wild boars serologically tested to Rickettsia spp. in this type of study. Among the 106 seroreactive animals, 34 showed possible homologous reactions between R. parkeri, R. amblyommatis, and R. bellii, with endpoint titers between 128 and 512. A sample of 45 ticks collected from four culled wild boars was identified as Amblyomma sculptum, and all tested negative for rickettsial DNA presence. In conclusion, this study has provided a reliable sampling seroprevalence and indicated high exposure of wild boars to rickettsial agents, with a potential interaction with Rickettsia spp. from the spotted fever group within the Cerrado biome from midwestern Brazil.

An expanded genetic toolkit for inducible expression and targeted gene silencing in Rickettsia parkeri

Pathogenic species within the Rickettsia genus are transmitted to humans through arthropod vectors and cause a spectrum of diseases ranging from mild to life-threatening. Despite rickettsiae posing an emerging global health risk, the genetic requirements of their infectious life cycles remain poorly understood. A major hurdle toward building this understanding has been the lack of efficient tools for genetic manipulation, owing to the technical difficulties associated with their obligate intracellular nature. To this end, we implemented the Tet-On system to enable conditional gene expression in Rickettsia parkeri. Using Tet-On, we show inducible expression of antibiotic resistance and a fluorescent reporter. We further used this inducible promoter to screen the ability of R. parkeri to express four variants of the catalytically dead Cas9 (dCas9). We demonstrate that all four dCas9 variants can be expressed in R. parkeri and used for CRISPR interference (CRISPRi)-mediated targeted gene knockdown. We show targeted knockdown of an antibiotic resistance gene as well as the endogenous virulence factor sca2. Altogether, we have developed systems for inducible gene expression and CRISPRi-mediated gene knockdown for the first time in rickettsiae, laying the groundwork for more scalable, targeted mechanistic investigations into their infectious life cycles.IMPORTANCEThe spotted fever group of Rickettsia contains vector-borne pathogenic bacteria that are neglected and emerging threats to public health. Due to the obligate intracellular nature of rickettsiae, the development of tools for genetic manipulation has been stunted, and the molecular and genetic underpinnings of their infectious lifecycle remain poorly understood. Here, we expand the genetic toolkit by introducing systems for conditional gene expression and CRISPR interference (CRISPRi)-mediated gene knockdown. These systems allow for relatively easy manipulation of rickettsial gene expression. We demonstrate the effectiveness of these tools by disrupting the intracellular life cycle using CRISPRi to deplete the sca2 virulence factor. These tools will be crucial for building a more comprehensive and detailed understanding of rickettsial biology and pathogenesis.

Whole genome sequence and comparative genomic analysis of novel Rickettsia koreansis strain CNH17-7 isolated from human

PURPOSE

To determine the genomic feature of novel spotted fever-causing Rickettsia koreansis strain CNH17-7, which is different from R. japonica that is a causative agent for Japanese spotted fever (JSF), and to perform its comparative genomic analysis.

METHODS

Whole genome sequencing (WGS) was performed on R. koreansis strain CNH17-7 by using the Illumina Miseq system. After WGS, assembly and annotation were done by SPAdes. Then, its genomic features were compared with 19 different Rickettsia species. Based on the average nucleotide identity (ANI) value, an unweighted pair group method with an arithmetic mean (UPGMA) dendrogram was generated. Following the dendrogram analysis, pan-and core-genome analysis was performed. Then additional comparative analyses with two genetically closest Rickettsia species were conducted based on gene repertoire.

RESULTS

R. koreansis strain CNH17-7 has a chromosome consisting of 1,392,633 bp with GC content of 32.4%. The ANI-derived UPGMA showed that R. koreansis strain CNH17-7 is genetically close to R. japonica YH and R. heilongjiangensis 054 but is distinctively differentiated. The ANI value of R. koreansis strain CNH17-7 to R. japonica YH and R. heilongjiangensis 054 are 98.14% and 98.04% respectively, indicating R. koreansis strain CNH17-7 is sufficient to be classified as a new species. Other than ANI, R. koreansis strain CNH17-7 also contains novel CDS and its COG functional category proportion which is distinct compared to R. japonica YH and R. heilongjiangensis 054.

CONCLUSION

We have revealed genomic features of the novel R. koreansis strain CNH17-7. Hence, we propose R. koreansis strain CNH17-7 as new Rickettsia species.

Cell-selective proteomics reveal novel effectors secreted by an obligate intracellular bacterial pathogen

Pathogenic bacteria secrete protein effectors to hijack host machinery and remodel their infectious niche. Rickettsia spp. are obligate intracellular bacteria that can cause life-threatening disease, but their absolute dependence on the host cell has impeded discovery of rickettsial effectors and their host targets. We implemented bioorthogonal non-canonical amino acid tagging (BONCAT) during R. parkeri infection to selectively label, isolate, and identify effectors delivered into the host cell. As the first use of BONCAT in an obligate intracellular bacterium, our screen more than doubles the number of experimentally validated effectors for the genus. The seven novel secreted rickettsial factors (Srfs) we identified include Rickettsia-specific proteins of unknown function that localize to the host cytoplasm, mitochondria, and ER. We further show that one such effector, SrfD, interacts with the host Sec61 translocon. Altogether, our work uncovers a diverse set of previously uncharacterized rickettsial effectors and lays the foundation for a deeper exploration of the host-pathogen interface.

The Impact of Altitude on Tick-Borne Pathogens at Two Mountain Ranges in Central Slovakia

Ticks are ectoparasites of a wide range of animals and are important vectors of numerous pathogens affecting humans, livestock, and pets. This study investigates possible correlations between selected factors, altitude, soil pH, and a factor called 'amount' (number of ticks examined in pooled samples) on the occurrence of I. ricinus ticks positive for selected tick-borne microorganisms. Questing I. ricinus ticks were collected in 2016 and 2017 across various altitudes, at two mountain ranges in central Slovakia. Tick pools were screened for the presence of Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato (Bbsl), Babesia/Theileria spp., Rickettsia spp., and tick-borne encephalitis virus (TBEV) using molecular methods. Regression analysis was employed to evaluate relationships between selected factors and the occurrence of vector-borne microorganisms. This study revealed a statistically significant influence of altitude on the occurrence of A. phagocytophilum; increasing altitude of the sampling site was associated with increased probability of pathogen occurrence. For Babesia/Theileria spp., neither altitude nor soil pH significantly affected pathogen occurrence. The occurrence of Bbsl was notably impacted by both altitude and soil pH; higher altitudes were associated with a decreased probability of pathogen presence, whereas higher soil pH increased the likelihood of pathogen occurrence. The presence of Rickettsia in a pooled sample was not affected by altitude and soil pH, but the 'amount' factor was a significant predictor, increasing the probability of pathogen detection. Neither altitude nor soil pH had a significant impact on TBEV occurrence. The regression models showed moderate goodness-of-fit levels to the data, underscoring their utility in examining the role of altitude and soil pH on pathogen occurrence. However, they explained only a small portion of the overall variance in pathogen occurrence, indicating the presence of other significant factors not covered in this study.

Molecular Identification of Spotted Fever Group Rickettsiae in Ticks in the Republic of Korea

The Rickettsia species transmitted by ticks are mostly classified within the spotted fever group rickettsiae (SFGR), which causes tick-borne rickettsiosis. Although efforts have been made to investigate their prevalence in the Republic of Korea (ROK), research has been limited to certain areas. Furthermore, the pooling method for ticks does not fully reflect the exact infection rate. Therefore, we aimed to perform molecular identification of SFGR in ticks to elucidate the current prevalence of tick-borne rickettsiosis in the ROK. The SFGR of ticks was identified using polymerase chain reaction targeting the 17 kDa antigen, ompA, and gltA, followed by sequencing for species identification and phylogenetic analysis. In total, 302 ticks belonging to four species (Haemaphysalis flava, H. longicornis, Ixodes nipponensis, and Amblyomma testudinarium) were collected between April and November 2022. The overall SFGR infection rate was 26.8% (81/302 patients). Both adult and nymphal ticks and the SFGR infection rate increased during April-May, reaching their peaks in June, followed by a marked decline in August and July, respectively. Phylogenetic analysis revealed three species (R. monacensis, R. heilongjiangensis, and Candidatus R. jingxinensis) of SFGR. Thus, our results emphasize the importance of tick surveys for the prevention and management of tick-borne rickettsiosis.

The influence of forest habitat type on Ixodes ricinus infections with Rickettsia spp. in south-western Poland

This study investigates the prevalence of Rickettsia spp. in Ixodes ricinus tick populations in different forest habitat types (broadleaf forest, mixed broadleaf and coniferous forest, and coniferous forest) in south-western Poland. During the survey periods from April to June 2018 and 2019 a total of 494 I. ricinus ticks, including 374 nymphs, 60 females and 60 males, were tested for Rickettsia infections by nested PCR targeting the gltA gene. The overall infection rate was 42.3%; however, we observed statistically significant year-to-year variation. Infection rates varied between tick developmental stages and were significantly influenced by forest habitat type. As assessed by a generalized linear mixed model (GLMM), the highest infection rates were observed in mixed broadleaf and coniferous forests, while coniferous forests had a significant negative effect on infection prevalence. DNA sequencing of selected samples confirmed the predominance of Rickettsia helvetica (91.2%) and less frequent Rickettsia monacensis (8.8%). This study suggests that the forest habitat types can influence Rickettsia spp. infection in tick populations; however, a comprehensive understanding of all factors influencing the level of infection requires future study.

Island hitchhikers: pathogen agents of Madeira and Azores ticks

Ticks are blood-sucking arthropods that can transmit pathogens to their host. As insular ecosystems can enhance tick-host interactions, this study aimed to understand tick diversity, pathogen presence, and their respective associations in the Azores and Madeira archipelagos. Unfed or partially engorged ticks (n = 120) were collected from 58 cats and dogs in the Azores (n = 41 specimens) and Madeira (n = 79 specimens) from November 2018 to March 2019. Vector identification was based on morphology and molecular criteria. For pathogen sequencing, 18S gene fragment for Babesia/Hepatozoon and gltA for Rickettsia were performed. Sequence data was explored using BLAST and BLAST and phylogenetic inference tools. In the Azores, Ixodes hexagonus, I. ventalloi, and Rhipicephalus sanguineus (n = 6; 14.6%, n = 6; 14.6%, and n = 29; 70.7% respectively) were found and in Madeira I. ricinus and R. sanguineus (n = 78, 98.7%; and n = 1, 1.3%; respectively) were identified. Tick COI markers confirmed species highlighting confirmation of R. sanguineus s.s. and genotype A of I. ventalloi. In the Azores Islands, the detected Rickettsia massiliae was linked to R. sanguineus (dogs and cats) and I. hexagonus (dogs), and in Madeira Island, R. monacensis (dogs) and Hepatozoon silvestris (cats) were found associated with I. ricinus. Further, I. ventalloi presence in the Azores expands west its known range, and Hepatozoon silvestris in Madeira may suggest that I. ricinus could have a role as a potential vector. Finally, as R. massiliae and R. monacensis presence underlines public health risks, surveillance by health authorities is crucial as pathogen-tick interactions may drive disease spread, therefore monitoring remains pivotal for disease prevention.

Rickettsia africae infections in sub-Saharan Africa: A systematic literature review of epidemiological studies and summary of case reports

Rickettsia africae is a tick-borne bacteria known to cause African tick bite fever (ATBF). While the disease was first described more than 100 years ago, knowledge of transmission risk factors and disease burden remain poorly described. To better understand the burden of R. africae, this article reviewed and summarized the published literature related to ATBF epidemiology and clinical management. Using a systematic approach, consistent with the PRISMA guidelines, we identified more than 100 eligible articles, including 65 epidemiological studies and 41 case reports. Most reports described R. africae in ticks and livestock, while human studies were less common. Human disease case reports were exclusively among returning travellers from non-endemic areas, which limits our disease knowledge among at-risk populations: people living in endemic regions. Substantial efforts to elucidate the ATBF risk factors and clinical manifestations among local populations are needed to develop effective preventative strategies and facilitate appropriate and timely diagnosis.

The case of Mediterranean spotted fever of the traveler returned from Zambia

We report the case of a traveler who returned from Zambia and was diagnosed with Mediterranean spotted fever (MSF), an infectious disease caused by Rickettsia conorii conorii. The patient presented to Sapporo City General Hospital with symptoms of fever, malaise, headache, and rash. The pathogen was identified by Polymerase Chain Reaction assays and subsequent analyses. The patient improved with 10-day treatment of oral doxycycline. Although some cases of MSF have been reported in sub-Saharan Africa, none have been reported in Zambia. Rhipicephalus sanguineus sensu lato, the vector of the Rickettsia conorii conorii, has been found in various areas of Zambia. Our case report highlights the potential threat of Mediterranean spotted fever in urban areas of Zambia.

Description of Rhipicephalus hibericus sp. nov. (Ixodoidea: Ixodidae), a species of the Rhipicephalus sanguineus group in southwestern Europe

We describe all the life stages of Rhipicephalus hibericus n. sp., provide the types, and present molecular support for a new species of the Rhipicephalus sanguineus sensu lato group, present in southwestern Europe, that has been historically confused with Rhipicephalus turanicus Pomerantzev, 1940. A new name is proposed for this taxon because it was impossible to ascribe to types of already described species in the group, deposited for more than 100 years in natural history institutions. The males have a dorsum showing deep and coarse punctations (absent in Rhipicephalus sanguineus sensu stricto) and adanal plates with large punctations (absent in R. sanguineus s.s.); the tail of the spiracular plate is as wide as the closest festoon (half the width in R. sanguineus s.s.). Females have large punctations in dorsal fields, a wide spiracular plate, and a "V" shaped genital opening; such a combination of characters cannot be found in other species of the group. Immatures are described from specimens collected on hosts (Rodentia and Eulipotyphla). Both larvae and nymphs are markedly smaller than R. sanguineus s.s. Nymphs display long, backward-projected auriculae; larvae are almost half the size of R. sanguineus s.s. The new species can hybridize with R. sanguineus s.s. in laboratory colonies producing an unfertile F2, laying brown and dry eggs that did not hatch. Phylogenetic analysis of partial coxI gene sequences placed R. hibericus in a well-supported clade with other sequences of R. sanguineus s.l. from Portugal, as a sister clade of R. sanguineus s.s. The new species does not belong to the R. turanicus group of species. Both 12S and 16S partial gene sequences were not as precise in the correct phylogenetic placement of R. hibericus, in part probably due to the existence of erroneously identified sequences in GenBank©. This description, together with the previous reinstatement of Rhipicephalus secundus and Rhipicephalus rutilus, and the description of the neotypes of R. sanguineus s.s. should help researchers to adequately identify their collections. Our findings demonstrate that R. turanicus is absent in southwestern Europe. Old collections should be re-examined to provide the actual range of the new species.

Evaluating the circulation of Ehrlichia canis and Rickettsia spp. in domestic dogs from a semiarid region in Brazil

Tick-borne diseases are important for animal and human health, because they can cause death if not diagnosed and treated early. Canine monocytic ehrlichiosis (CME) can cause high morbidity in dog populations. Rocky Mountain Spotted Fever (RMSF) is among the most virulent infectious in humans; dogs are also susceptible to infection. The aims of this study were to evaluate the presence of Ehrlichia canis and Rickettsia spp. infections in domestic dogs, and to identify tick species parasitizing dogs among urban areas of two municipalities (Sobral and Alcântaras) in the Ceará State, Northeastern Brazil. A total of 208 domiciled dogs was sampled. After clinical evaluation, blood samples and ticks were collected and submitted to Real-Time Polymerase Chain Reaction (RT-PCR) targeting E. canis DNA. Serum samples were screened by Indirect Immunofluorescence Assays (IFA) for antibodies against different strains of Rickettsia spp. previously recognized in Brazil. The results of this study indicate the molecular detection of E. canis in the state of Ceará, Brazil, where the proportion of canine infection in Sobral (9.9%) was higher than in Alcântaras (5.6%). Rhipicephalus sanguineus sensu lato was the prevalent tick species infesting the dogs in both municipalities (43.5 and 53.3%, respectively). Our serological results indicate that dogs of the study area were at low risk of exposure to these tick-borne Rickettsia spp. of the spotted fever group. Our study offers epidemiological data of these diseases to better understanding Rickettsiales epidemic and enzootic cycles in the Brazilian semiarid region, improving prevention and control measures.

Tick-Borne Bacterial Diseases in Europe: Threats to public health

BACKGROUND

Tick-borne diseases, caused by bacterial pathogens, pose a growing threat to public health in Europe. This paper provides an overview of the historical context of the discovery of the most impactful pathogens transmitted by ticks, including Borrelia burgdorferi sensu lato, Rickettsia spp., Anaplasma spp., Francisella spp., Ehrlichia spp., and Neoehrlichia mikurensis. Understanding the historical context of their discovery provides insight into the evolution of our understanding of these pathogens.

METHODS AND RESULTS

Systematic investigation of the prevalence and transmission dynamics of these bacterial pathogens is provided, highlighting the intricate relationships among ticks, host organisms, and the environment. Epidemiology is explored, providing an in-depth analysis of clinical features associated with infections. Diagnostic methodologies undergo critical examination, with a spotlight on technological advancements that enhance detection capabilities. Additionally, the paper discusses available treatment options, addressing existing therapeutic strategies and considering future aspects.

CONCLUSIONS

By integrating various pieces of information on these bacterial species, the paper aims to provide a comprehensive resource for researchers and healthcare professionals addressing the impact of bacterial tick-borne diseases in Europe. This review underscores the importance of understanding the complex details influencing bacterial prevalence and transmission dynamics to better combat these emerging public health threats.

A conserved interaction between the effector Sca4 and host endocytic machinery suggests additional roles for Sca4 during rickettsial infection

Intracellular bacterial pathogens deploy secreted effector proteins that manipulate diverse host machinery and pathways to promote infection. Although many effectors carry out a single specific function or interaction, there are a growing number of secreted pathogen effectors capable of interacting with multiple host factors. However, few effectors secreted by obligate intracellular Rickettsia species have been linked to multiple host targets. Here, we investigated the conserved rickettsial secreted effector Sca4, which was previously shown to interact with host vinculin to promote cell-to-cell spread in the model Rickettsia species R. parkeri . We discovered that Sca4 also binds the host cell endocytic factor clathrin heavy chain (CHC, CLTC ) via a conserved segment in the Sca4 N-terminus. Ablation of CLTC expression or chemical inhibition of endocytosis reduced R. parkeri cell-to-cell spread, indicating that clathrin promotes efficient spread between mammalian cells. This activity was independent of Sca4 and appeared restricted to the recipient host cell, suggesting that the Sca4-clathrin interaction also regulates another aspect of the infectious lifecycle. Indeed, R. parkeri lacking Sca4 or expressing a Sca4 truncation unable to bind clathrin had markedly reduced burdens in tick cells, hinting at a cell-type specific function for the Sca4-clathrin interaction. Sca4 homologs from diverse Rickettsia species also bound clathrin, suggesting that the function of this novel effector-host interaction may be broadly important for rickettsial infection. We conclude that Sca4 has multiple targets during infection and that rickettsiae may manipulate host endocytic machinery to facilitate several stages of their life cycles.

American mitogenome reference for the tropical brown dog tick, Rhipicephalus linnaei (Audouin, 1826)

The brown dog tick, Rhipicephalus linnaei (Audouin, 1826), is distributed across the American continent and is formerly known as the "tropical lineage". It belongs to the Rhipicephalus sanguineus (Latreille, 1806) species complex, referred to as R. sanguineus (sensu lato). Mitochondrial genome sequences are frequently used for the identification and represent reference material for field studies. In the present study, the entire mitochondrial genomes of R. linnaei (∼15 kb) collected from dogs in Mexico were sequenced and compared with available mitogenomes of R. sanguineus (s.l.). The mitochondrial genome is ∼90% identical to the reference genome of R. sanguineus (sensu stricto, former "temperate lineage") and > 99% identical to R. linnaei mitogenome derived from the neotype. Two additional mitogenomes were obtained and described as R. linnaei and R. turanicus from dogs in Saudi Arabia. The present study delivers a molecular reference for R. linnaei from America and complements R. linnaei mitogenomes from Africa, Asia and Australia. We propose to consider the complete mitogenome, as the reference for American R. linnaei, even when partial mitochondrial cox1, 12S rRNA or 16S rRNA genes are characterised.

Molecular identification of Borrelia and SFG Rickettsia spp. in hard ticks parasitizing domestic and wild animals in southeastern Spain

Lyme disease and the spotted fever group rickettsiosis, involve bacteria belonging to the genus Borrelia and Rickettsia, respectively. These infections are the most important tick-borne zoonotic diseases involving ticks as vectors. Descriptive and epidemiological studies are essential to determine the animal hosts involved in the maintenance of these diseases. In the present study, 94 tick pool samples from 15 different host species located in the Region of Murcia (southeastern, Spain) were analysed. Ticks were morphologically identified as: Dermacentor marginatus, Hyalomma lusitanicum, Ixodes Ricinus, and Rhipicephalus sanguineus. Our results showed that 5.3% of the tick pool samples carried Borrelia spp. DNA, and 20.2% carried SFG Rickettsia DNA. In every hard tick pool Spot Fever Group (SFG) Rickettsia spp. DNA were detected, except for H. lusitanicum. Likewise, D. marginatum was the only species in which Borrelia spp. DNA was not detected. Barbary sheep and wild boar were the host species in which tick pools showed DNA presence of both pathogens. This study increases the knowledge about the presence of Borrelia spp. DNA and SFG Rickettsia spp. DNA in different hard tick species from this geographical area.

Cervids as Sentinels for Rickettsia spp. in Portugal

Cervids are highly exposed to ticks, however, their role in the life cycle of these rickettsiae has not been fully elucidated. Given the expanding distribution and growing population of deer species in Portugal, coupled with their direct and indirect interactions with humans during hunting, it becomes crucial to explore their role as sentinels and potential reservoirs of Rickettsia. The present investigation aimed to detect and evaluate exposure to Rickettsia in free-living deer from Portugal. Blood samples (n = 77) were collected from hunted game animals (red deer and fallow deer) from different areas throughout Portugal (Idanha-a-Nova, Monte Fidalgo, Montalvão and Arraiolos) and sera were tested by immunofluorescence assay, to detect antibodies. Additionally, blood DNA samples were screened for SFGR by nested-polymerase chain reaction targeting a fragment of the outer membrane protein B (ompB) gene, as well as for Anaplasma and Ehrlichia spp. targeting the 16S rRNA gene. Thirty-five per cent (25 deer and two fallow deer) tested positive (sera with a titer ≥1:64) for IgG antibodies against Rickettsia conorii. No rickettsial DNA was detected by PCR for the ompB gene, and all DNA samples tested negative for Anaplasma and Ehrlichia. As far as we know, this study is the first screening of cervid species in Portugal for Rickettsia antibodies. The findings suggest that these animals serve as useful sentinel indicators for the circulation of rickettsiae, offering a complementary perspective to studies focused on ticks. The increasing numbers of hunted deer in Portugal and the potential zoonotic features of Rickettsia spp. highlight the importance of continued surveillance directed at tick-borne diseases, especially those involving wild animals.

Detection of tick-borne pathogens in Rhipicephalus bursa ticks collected from the autochthonous Garrano breed of horses in Portugal

The Garrano is a semi-feral horse breed native to several mountains in the northern Iberian Peninsula. Despite being endangered, this unique breed of pony has managed to survive in the wild and continues to be selectively bred, highlighting their remarkable resilience and adaptability to harsh environments. Wildlife plays a critical role in the survival of tick vectors in their natural habitats and the transfer of tick-borne pathogens, as they can serve as reservoir hosts for many agents and amplifiers for these vectors. The semi-feral lifestyle of the Garrano horses makes them particularly vulnerable to exposure to numerous tick species throughout the year. Therefore, the aim of this study was to investigate the occurrence of Anaplasma, Ehrlichia, Babesia, Theileria, and spotted fever rickettsiae in the Garrano horse ticks to obtain a knowledge of circulating agents in this host population. The collected ticks (n = 455) were identified as Rhipicephalus bursa. DNA specimens were organized in pools of 5 ticks, for molecular screening. Pools PCR results confirmed the presence of Candidatus Rickettsia barbariae (n = 12 for the ompB gene, n = 11 for the ompA gene and n = 6 for the gltA gene), Babesia bigemina (n = 1), Babesia caballi (n = 3), Theileria equi (n = 15) and Theileria haneyi (n = 1).These results confirm the circulation of an emerging rickettsial spotted fever group member, Candidatus R. barbariae, in R. bursa ticks. Our findings demonstrated that Candidatus R. barbariae co-circulates with B. bigemina and T. equi, which are vectored by R. bursa. We are reporting for the first time, the detection of T. haneyi among R. bursa ticks feeding in the Garrano horses in Portugal. Surveillance studies for tick-borne infections are essential to provide information that can facilitate the implementation of preventive and control strategies.

Distribution and pathogen prevalence of field-collected ticks from south-western Korea: a study from 2019 to 2022

Hard ticks are known vectors of various pathogens, including the severe fever with thrombocytopenia syndrome virus, Rickettsia spp., Coxiella burnetii, Borrelia spp., Anaplasma phagocytophilum, and Ehrlichia spp. This study aims to investigate the distribution and prevalence of tick-borne pathogens in southwestern Korea from 2019 to 2022. A total of 13,280 ticks were collected during the study period, with H. longicornis accounting for 86.1% of the collected ticks. H. flava, I. nipponensis and A. testudinarium comprised 9.4%, 3.6%, and 0.8% of the ticks, respectively. Among 983 pools tested, Rickettsia spp. (216 pools, 1.6% MIR) were the most prevalent pathogens across all tick species, with R. japonica and R. monacensis frequently detected in I. nipponensis and Haemaphysalis spp., respectively. Borrelia spp. (28 pools, 0.2% MIR) were predominantly detected in I. nipponensis (27 pools, 13.8% MIR, P < 0.001). Co-infections, mainly involving Rickettsia monacensis and Borrelia afzelii, were detected in I. nipponensis. Notably, this study identified R. monacensis for the first time in A. testudinarium in South Korea. These findings offer valuable insights into the tick population and associated pathogens in the region, underscoring the importance of tick-borne disease surveillance and prevention measures.

Pathogens Detected in Questing Ixodes ricinus Ticks in a Mountainous Area in Greece

Ixodes ricinus ticks are vectors of a plethora of pathogens. The purpose of this study was to screen 398 I. ricinus ticks for a variety of pathogens. Following the pooling, homogenization, and extraction of total nucleic acids, a real-time PCR was applied for the detection of a panel of tick-borne pathogens, while additional conventional PCRs combined with Sanger sequencing were applied for the detection of viruses and typing of Rickettsia and Borrelia species. At least one pathogen was detected in 60 of the 80 (75%) tick pools. Rickettsia spp. predominated, as it was detected in 63.75% of the pools (51/80; MIR 12.81%), followed by Borrelia spp. (35 pools (45%); MIR 8.79%), while Anaplasma phagocytophilum was detected in 2 pools (2.5%, MIR 0.5%). The ticks of six Rickettsia-positive pools were tested individually (from stored half-ticks); all sequences were identical to those of R. monacensis. Similarly, the ticks of six Borrelia-positive pools were tested individually, and it was shown that four belonged to the genospecies Borrelia garinii and two to Borrelia valaisiana. Phleboviruses were detected in 3 pools (3.75%; MIR 0.75%), with sequences clustering in the Ixovirus genus, while nairoviruses were detected in 7 pools (8.75%; MIR 1.76%), with one sequence clustering in the Orthonairovirus genus, and six clustering in the Norwavirus genus. Although a small number of ticks from only one area in Greece were tested, a variety of pathogens together with recently identified viruses were detected, prompting further studies in ticks and surveillance studies in humans.

Ticks and tick-borne diseases from Mallorca Island, Spain

Ixodid ticks are obligate blood-feeding arthropods and important vectors of pathogens. In Mallorca, almost no data on the tick fauna are available. Herein, we investigated ticks and tick-borne pathogens in ticks collected from dogs, a cat and humans in Mallorca as result of a citizen science project. A total of 91 ticks were received from German tourists and residents in Mallorca. Ticks were collected from March to October 2023 from dogs, cat and humans, morphologically and genetically identified and tested for pathogens by PCRs. Six tick species could be identified: Ixodes ricinus (n = 2), Ixodes ventalloi (n = 1), Hyalomma lusitanicum (n = 7), Hyalomma marginatum (n = 1), Rhipicephalus sanguineus s.l. (n = 71) and Rhipicephalus pusillus (n = 9). Rhipicephalus sanguineus s.l. adults were collected from dogs and four females from a cat and the 16S rDNA sequences identified it as Rh. sanguineus s.s. Hyalomma lusitanicum was collected from 1 human, 1 dog and 5 specimens were collected from the ground in the community of Santanyi, together with one H. marginatum male. This is the first report of Hyalomma marginatum in Mallorca. Both I. ricinus were collected from humans and I. ventalloi female was collected from a dog. All ticks tested negative for Anaplasma phagocytophilum, Coxiella spp., Francisella spp., and piroplasms. In 32/71 (45%) specimens of Rh. sanguineus s.s., Rickettsia spp. could be detected and in 18/32 (56.2%) sequenced tick DNAs R. massiliae was identified. Ixodes ventalloi female and both I. ricinus tested positive in the screening PCR, but the sequencing for the identification of the Rickettsia sp. failed.

Ixodiphagus hookeri (Hymenoptera: Encyrtidae) and Tick-Borne Pathogens in Ticks with Sympatric Occurrence (and Different Activities) in the Slovak Karst National Park (Slovakia), Central Europe

Ticks are involved in the transmission a plethora of pathogens. To effectively control ticks and mitigate the risks associated with tick-borne diseases, it is important to implement tick control measures. These may include the use of acaricides as well as the development and implementation of an alternative, environmentally friendly tick management program that include practices such as habitat modification or establishing biological control. Ixodiphagus hookeri Howard is a tick-specific parasitoid wasp that predates on several species of ixodid ticks and could contribute to the control of the tick population. This work aimed to detect the presence of parasitoid wasps in ticks (Ixodidae) using genetic approaches. Several tick species of the genera Ixodes, Haemaphysalis, and Dermacentor, with a sympatric occurrence in the Slovak Karst National Park in southeastern Slovakia, were screened for the presence of wasps of the genus Ixodiphagus. The DNA of the parasitoids was detected in four tick species from three genera. This work presents the first molecular detection of parasitoids in two Dermacentor tick species, as well as the first molecular identification of Ixodiphagus wasps in Ixodes ricinus and Haemaphysalis concinna ticks from the Karst area. In the given area, it was observed that I. ricinus and H. concinna ticks are hyper-parasitized by wasps. Moreover, it was observed that wasps here can parasitize several tick species, some of which are of less significance for human and animal health (as they transmit fewer pathogens).

The structure and behavioral patterns of the human population affected by ixodid tick bites in Irkutsk Region, Eastern Siberia, Russia

The bites of hard ticks are the major route of transmission of tick-borne infections to humans, causing thousands of cases of diseases worldwide. However, the characteristics of the human population that is exposed to tick bites are still understudied. This work is aimed at characterizing both the structure of the population directly contacting ticks and the human behavioral features associated with tick bites. We studied 25,970 individuals who sought medical help after a tick bite at the Centre for Diagnostics and Prevention of Tick-borne Infections (CDPTBI) in Irkutsk City (Russian Federation). The demographic and behavioral characteristics of the human population were analyzed using z-tests for proportions, the Mann-Whitney U test, and the Spearman rank correlation coefficient. The majority of bitten people were urban residents (70 %), and most of them were either of active ages between 30 and 74 years old (62 %), or children between 0 and 9 years old (approximately 20%). Tick bites occurred mostly in the range of 150 km around the location of the diagnostic facility (83 %). In comparison to the general population, significant differences were revealed in the representation of different age groups among bitten people. The population affected by tick bites included fewer men and women in the ages of 10-29 and over 75 years old than would be predicted based on the demographics of the general population. Vice versa, the proportions of people in the ages of 5-9 and 60-74 increased among bitten people. Among men, such activities (in order of occurrence) as "leisure and recreation", "visiting allotments", "foraging for forest food", and "fulfilling work duties" tend to be more associated with tick bites. Among women, tick bites occurred mainly during "visiting allotments", "leisure and recreation", "visiting cemeteries" and "contact with pets and plants at home". The overall vaccination rate was 12 %; however, significantly more men than women were vaccinated against tick-borne encephalitis (up to 20 % vs. approximately 7 % respectively). The structure of the tick bite - affected population suggests that it is age-specific human behavior that mainly determines the frequency of contact between people and ticks. However, in several age groups, especially among children from 5 to 9 and people aged 30-39 years old, gender-related factors could significantly change the exposure of people to tick bites.

Ticks (Acari: Ixodidae) and rickettsiae associated with wild boars in a rural area of Minas Gerais, Brazil

Wild boars or feral pigs are classified by the Brazilian Institute for the Environment and Renewable Resources (IBAMA) in "Category I of invasive exotic species". They cause economic losses, harm the environment, serve as hosts and reservoirs for several zoonotic disease agents, and provide a blood meal for tick species that act as vectors for zoonotic diseases. The objective of this study was to identify tick species on wild boars, assess host-seeking ticks in the related environment, and identify other potential tick hosts coexisting with wild boars on a farm located in the state of Minas Gerais, southeastern Brazil. Additionally, the study aimed to determine the presence of rickettsiae in these arthropods and assess the exposure of wild boars to rickettsiae species from the Spotted Fever Group and Rickettsia bellii through serology. A total of 3585 host-seeking ticks from three species (Amblyomma sculptum - 41.58%; Amblyomma dubitatum - 0.39% and Rhipicephalus microplus - 0.05%) were collected in the environment and A. sculptum was the most abundant species. Thirty-one wild boars were evaluated, resulting in the collection of 415 ticks, all of which were A. sculptum. Rickettsia DNA was not detected in samples of A. sculptum and R. microplus from the environment or in A. sculptum ticks from wild boars. However, all A. dubitatum ticks (n = 14) had Rickettsia bellii DNA confirmed by the species-specific PCR protocol. Out of the 31 serum samples from wild boars, 24 reacted with at least one Rickettsia antigen. Among these, seven individuals exhibited a reaction to a probable homologous antigen (PHA) of three rickettsiae species: R. rickettsii (n = 3), R. amblyommatis (n = 3) and R. rhipicephali (n = 1). Despite the high prevalence of seroreactivity, titers were low, indicating limited exposure to Rickettsia spp. Camera traps generated 874 animal records, capturing a total of 1688 individuals. At least 11 species of birds and 14 species of mammals (12 wild and two domestic) shared the environment with wild boars and potentially shared ticks with them. These findings provide baseline information for understanding the sharing of ticks and tick-borne pathogens between wild boars and other animals within the Cerrado biome. Further studies are necessary to monitor the potential and actual risk of wild boars to harbor infected ticks and their role in the transmission and maintenance cycle of Rickettsia spp.

Molecular Detection and Characterization of Rickettsia Species in Ixodid Ticks from Selected Regions of Namibia

Rickettsial pathogens are among the emerging and re-emerging vector-borne zoonoses of public health importance. Reports indicate human exposure to Rickettsial pathogens in Namibia through serological surveys, but there is a lack of data on infection rates in tick vectors, hindering the assessment of the relative risk to humans. Our study sought to screen Ixodid ticks collected from livestock for the presence of Rickettsia species in order to determine infection rates in ticks and to determine the Rickettsia species circulating in the country. We collected and pooled Hyalomma and Rhipicephalus ticks from two adjacent regions of Namibia (Khomas and Otjozondjupa) and observed an overall minimum Rickettsia infection rate of 8.6% (26/304), with an estimated overall pooled prevalence of 9.94% (95% CI: 6.5-14.3). There were no statistically significant differences in the estimated pooled prevalence between the two regions or tick genera. Based on the nucleotide sequence similarity and phylogenetic analysis of the outer membrane protein A (n = 9) and citrate synthase (n = 12) genes, BLAST analysis revealed similarity between Rickettsia africae (n = 2) and Rickettsia aeschlimannii (n = 11), with sequence identities ranging from 98.46 to 100%. Our initial study in Namibia indicates that both zoonotic R. africae and R. aeschlimannii are in circulation in the country, with R. aeschlimannii being the predominant species.

Italian peninsula as a hybridization zone of Ixodes inopinatus and I. ricinus and the prevalence of tick-borne pathogens in I. inopinatus, I. ricinus, and their hybrids

BACKGROUND

Ixodes inopinatus was described from Spain on the basis of morphology and partial sequencing of 16S ribosomal DNA. However, several studies suggested that morphological differences between I. inopinatus and Ixodes ricinus are minimal and that 16S rDNA lacks the power to distinguish the two species. Furthermore, nuclear and mitochondrial markers indicated evidence of hybridization between I. inopinatus and I. ricinus. In this study, we tested our hypothesis on tick dispersal from North Africa to Southern Europe and determined the prevalence of selected tick-borne pathogens (TBPs) in I. inopinatus, I. ricinus, and their hybrids.

METHODS

Ticks were collected in Italy and Algeria by flagging, identified by sequencing of partial TROSPA and COI genes, and screened for Borrelia burgdorferi s.l., B. miyamotoi, Rickettsia spp., and Anaplasma phagocytophilum by polymerase chain reaction and sequencing of specific markers.

RESULTS

Out of the 380 ticks, in Italy, 92 were I. ricinus, 3 were I. inopinatus, and 136 were hybrids of the two species. All 149 ticks from Algeria were I. inopinatus. Overall, 60% of ticks were positive for at least one TBP. Borrelia burgdorferi s.l. was detected in 19.5% of ticks, and it was significantly more prevalent in Ixodes ticks from Algeria than in ticks from Italy. Prevalence of Rickettsia spotted fever group (SFG) was 51.1%, with significantly greater prevalence in ticks from Algeria than in ticks from Italy. Borrelia miyamotoi and A. phagocytophilum were detected in low prevalence (0.9% and 5.2%, respectively) and only in ticks from Italy.

CONCLUSIONS

This study indicates that I. inopinatus is a dominant species in Algeria, while I. ricinus and hybrids were common in Italy. The higher prevalence of B. burgdorferi s.l. and Rickettsia SFG in I. inopinatus compared with that in I. ricinus might be due to geographical and ecological differences between these two tick species. The role of I. inopinatus in the epidemiology of TBPs needs further investigation in the Mediterranean Basin.

Spatially limited pathogen pollution in an invasive tick and host system

Expansion of global commerce has facilitated pathogen pollution via the transportation and translocation of invasive species and their associated parasites and pathogens. In Florida, imported cane toads (Rhinella horribilis) were accidentally and intentionally released on multiple occasions. Early populations were found to be infested with the invasive tick, Amblyomma rotundatum, yet it is unknown if these ticks dispersed with their hosts as cane toads spread throughout much of the state. The objectives of our investigation were to (1) determine if there are fewer tick infestations on toads at the periphery than at the core of their distribution as predicted by founder effect events, and (2) identify if ticks were infected with exotic pathogens. We captured toads from 10 populations across Florida. We collected ticks, vent tissue, and tick attachment site tissue from each toad, then tested samples for bacteria in the genus, Rickettsia. We found that 3/10 populations had toads that were infested with A. rotundatum, and infested individuals were in the earliest introduced populations at the core of their distribution. Pathogen testing confirmed Rickettisa bellii in ticks, but not in toad tissues. Haplotype networks could not clearly distinguish if R. bellii in Florida was more closely related to North or South American strains, but host-tick associations suggest that the pathogen was exotic to Florida. Our investigation demonstrated that an invasive species facilitated the introduction of parasites and pathogens into Florida, yet the invasive tick species encountered limitations to dispersal on this host species.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10530-024-03291-9.

Prevalence of tick-borne pathogens in ticks collected from the wild mountain ungulates mouflon and chamois in 4 regions of France

Ticks are major vectors of various pathogens of health importance, such as bacteria, viruses and parasites. The problems associated with ticks and vector-borne pathogens are increasing in mountain areas, particularly in connection with global climate change. We collected ticks (n = 2,081) from chamois and mouflon in 4 mountainous areas of France. We identified 6 tick species: Ixodes ricinus, Rhipicephalus bursa, Rh. sanguineus s.l., Haemaphysalis sulcata, H. punctata and Dermacentor marginatus. We observed a strong variation in tick species composition among the study sites, linked in particular to the climate of the sites. We then analysed 791 ticks for DNA of vector-borne pathogens: Babesia/Theileria spp., Borrelia burgdorferi s.l., Anaplasma phagocytophilum, A. marginale, A. ovis, and Rickettsia of the spotted fever group (SFG). Theileria ovis was detected only in Corsica in Rh. bursa. Babesia venatorum (2 sites), Borrelia burgdorferi s.l. (B. afzelii and B. garinii; 2 sites) and Anaplasma phagocytophilum (3 sites) were detected in I. ricinus. Anaplasma ovis was detected at one site in I. ricinus and Rh. sanguineus s.l. SFG Rickettsia were detected at all the study sites: R. monacensis and R. helvetica in I. ricinus at the 3 sites where this tick is present; R. massiliae in Rh. sanguineus s.l. (1 site); and R. hoogstraalii and Candidatus R. barbariae in Rh. bursa in Corsica. These results show that there is a risk of tick-borne diseases for humans and domestic and wild animals frequenting these mountain areas.

TRIM56-mediated production of type I interferon inhibits intracellular replication of Rickettsia rickettsii

Rickettsia rickettsii (R. rickettsii), the causative agent of Rocky Mountain spotted fever (RMSF), is the most pathogenic member among Rickettsia spp. Previous studies have shown that tripartite motif-containing 56 (TRIM56) E3 ligase-induced ubiquitination of STING is important for cytosolic DNA sensing and type I interferon production to induce anti-DNA viral immunity, but whether it affects intracellular replication of R. rickettsii remains uncharacterized. Here, we investigated the effect of TRIM56 on HeLa and THP-1 cells infected with R. rickettsii. We found that the expression of TRIM56 was upregulated in the R. rickettsii-infected cells, and the overexpression of TRIM56 inhibited the intracellular replication of R. rickettsii, while R. rickettsii replication was enhanced in the TRIM56-silenced host cells with the reduced phosphorylation of IRF3 and STING and the increased production of interferon-β. In addition, the mutation of the TRIM56 E3 ligase catalytic site impairs the inhibitory function against R. rickettsii in HeLa cells. Altogether, our study discovers that TRIM56 is a host restriction factor of R. rickettsii by regulating the cGAS-STING-mediated signaling pathway. This study gives new evidence for the role of TRIM56 in the innate immune response against intracellular bacterial infection and provides new therapeutic targets for RMSF.

IMPORTANCE

Given that Rickettsia rickettsii (R. rickettsii) is the most pathogenic member within the Rickettsia genus and serves as the causative agent of Rocky Mountain spotted fever, there is a growing need to explore host targets. In this study, we examined the impact of host TRIM56 on R. rickettsii infection in HeLa and THP-1 cells. We observed a significant upregulation of TRIM56 expression in R. rickettsii-infected cells. Remarkably, the overexpression of TRIM56 inhibited the intracellular replication of R. rickettsii, while silencing TRIM56 enhanced bacterial replication accompanied by reduced phosphorylation of IRF3 and STING, along with increased interferon-β production. Notably, the mutation of the TRIM56's E3 ligase catalytic site did not impede R. rickettsii replication in HeLa cells. Collectively, our findings provide novel insights into the role of TRIM56 as a host restriction factor against R. rickettsii through the modulation of the cGAS-STING signaling pathway.

Grazing system and Hyalomma marginatum tick infestation in cattle with high prevalence of SFG Rickettsia spp

Tick-borne diseases (TBDs) represent a significant portion of infectious diseases of global public health interest. In Italy, knowledge about the occurrence of tick-borne pathogens (TBPs) in ticks parasitizing cattle is scarce. In this research, we focused on ticks infesting Maremmana cattle grazing in open pasture and silvopasture systems. After being morphologically identified, ticks were molecularly tested for the presence of pathogens of the genus Rickettsia. Of the 794 ticks detected, 117 were collected, being the majority Hyalomma marginatum (72.6%), followed by other Hyalomma species (23%), Rhipicephalus turanicus (1.7%), Rh. bursa (0.9%), Hy. lusitanicum (0.9%) and Dermatocentor marginatus (0.9%). All ticks were adults, 58.1% males and 41.8% females. The highest tick prevalence was noted in April for silvopasture system cattle (90%), and in May for open pasture ones (85%). TBPs were detected only in Hy. marginatum, and all belong to Rickettsia spp. of zoonotic interest. In particular, 21/40 (52.5%) ticks scored positive for Rickettsia spp. by gltA gene and of these 15/21 (71.4%) also to spotted fever group (SFG) rickettsiae by ompA gene. Of the total positive specimens, 19 were successfully sequenced and scored Rickettsia aeschilimannii (17/19, 89.5%), R. slovaca (1/19, 5%), and R. massiliae (1/19, 5%). This research highlights the potential impact of grazing systems on cattle parasitization by hard ticks. The molecular investigation of TBPs in ticks collected from Maremmana cattle shed light on the presence of pathogenic bacteria of SFG Rickettsia spp., pointing out the potential risk of TBPs transmission between livestock and humans.

Molecular and next-generation sequencing analysis of tick-borne pathogens of Rhipicephalus ticks (Acari: Ixodidae) in cattle and dogs

Ticks are small and adaptable arachnid ectoparasites and global carriers of various pathogens that threaten both human and animal health. They are present in many parts of China. A total of 858 ticks were collected from various regions and hosts, then subjected to species identification based on morphological and molecular characteristics, as described in the authors' previous study. Eighty-three individual tick samples were selected for screening pathogens based on metagenomic next-generation sequencing (mNGS) and polymerase chain reaction (PCR) assays. The genomic DNA of tick species was extracted, and amplification of the bacterial 16S rRNA gene was carried out from DNA of individual ticks using V3-V4 hypervariable regions, before subjecting to metagenomic analysis. Each tick underwent specific PCR tests for identifying the bacterial species present, including Anaplasma, Ehrlichia, Coxiella, and Rickettsia, and also protozoans such as Babesia, Theileria, and Hepatozoon. Illumina NovaSeq sequencing results revealed that the dominant phylum and family in Rhipicephalus spp. were Bacteroidota and Muribaculaceae, respectively. Alpha diversity patterns varied depending on tick sex (R. linnaei only), species and location, but not on host. Furthermore, bacterial pathogens, including A. marginale (58 %, 29/50), A. platys (6 %, 3/50), E. minasensis (2 %, 1/50), Ehrlichia sp. (10 %, 5/50), T. sinensis (24 %, 12/50), T. orientalis (54 %, 27/50) and Coxiella-like bacteria (CLB) (80 %, 40/50) were detected in R. microplus, while E. canis (33.33 %, 10/30), H. canis (20 %, 6/30) and CLB (100 %, 30/30) were detected in R. linnaei. Also, Anaplasma sp. (33.33 %, 1/3), A. marginale (33.33 %, 1/3), R. felis (33.33 %, 1/3) and CLB (100 %, 3/3) were detected in R. haemaphysaloides. Dual and triple co-infections involving pathogens or CLB were detected in 84.00 % of R. microplus, 66.66 % of R. haemaphysaloides, and 33.00 % of R. linnaei. The report on microbial communities and pathogens, which found from Rhipicephalus spp. in Hainan Island, is an important step towards a better understanding of tick-borne disease transmission. This is the first report in the area on the presence of Anaplasma sp., A. marginale, R. felis and Coxiella, in R. haemaphysaloides.

An expanded genetic toolkit for inducible expression and targeted gene silencing in Rickettsia parkeri

Pathogenic species within the Rickettsia genus are transmitted to humans through arthropod vectors and cause a spectrum of diseases ranging from mild to life-threatening. Despite rickettsiae posing an emerging global health risk, the genetic requirements of their infectious life cycles remain poorly understood. A major hurdle toward building this understanding has been the lack of efficient tools for genetic manipulation, owing to the technical difficulties associated with their obligate intracellular nature. To this end, we implemented the Tet-On system to enable conditional gene expression in Rickettsia parkeri. Using Tet-On, we show inducible expression of antibiotic resistance and a fluorescent reporter. We further used this inducible promoter to screen the ability of R. parkeri to express four variants of the catalytically dead Cas9 (dCas9). We demonstrate that all four dCas9 variants can be expressed in R. parkeri and used for CRISPR interference (CRISPRi)-mediated targeted gene knockdown. We show targeted knockdown of an antibiotic resistance gene as well as the endogenous virulence factor sca2. Altogether, we have developed systems for inducible gene expression and CRISPRi-mediated gene knockdown for the first time in rickettsiae, laying the groundwork for more scalable, targeted mechanistic investigations into their infectious life cycles.

Genotyping of ticks: first molecular report of Hyalomma asiaticum and molecular detection of tick-borne bacteria in ticks and blood from Khyber Pakhtunkhwa, Pakistan

Multiple ticks (Acari: Ixodoidea) carrying Rickettsiales bacteria have significant importance for both human and animal health. Thus, the purpose of this work was to genetically analyze tick species and their associated Rickettsiales bacteria in animal hosts. In order to achieve these objectives, various animals (including camels, cattle, goats, sheep, dogs, and mice) were inspected in four districts (Mardan, Peshawar, Kohat, and Karak) of Khyber Pakhtunkhwa to collect ticks, while blood samples were collected from all the symptomatic and asymptomatic cattle in all four districts. A total of 234 ticks were obtained from 86 out of 143 (60.14%) host animals, which were morphologically identified as Rhipicephalus turanicus, Rhipicephalus microplus, Haemaphysalis cornupunctata, and Hyalomma asiaticum. Among these, their representative ticks (126/234, 53.85%) were processed for molecular confirmation using cytochrome c oxidase (cox1) gene. Obtained cox1 sequences of four different tick species showed 99.72%-100% maximum identity with their corresponding species reported from Pakistan, China, India, and Kazakhstan and clustered phylogenetically. This study presented the first genetic report of Hy. asiaticum ticks in Pakistan. Moreover, genetically confirmed tick species were molecularly analyzed by PCR for detection of Rickettsiales DNA using partial fragments of 16S rDNA, 190-kDa outer membrane protein A (ompA), and 120-kDa outer membrane protein B (ompB) genes. In addition, blood samples were analyzed to identify Rickettsiales bacteria using the aforementioned genes. Rickettsiales bacteria were found in 24/126 (19.05%) ticks and 4/16 (25.00%) in symptomatic cattle's blood. The obtained ompA and ompB sequences from Hy. asiaticum ticks showed 99.73%-99.87% with Candidatus Rickettsia shennongii and unidentified Rickettsia sp., whereas the obtained 16S rDNA sequences from cattle's blood and ticks (Hae. cornupunctata) showed 99.67% highest identity with Anaplasma phagocytophilum. The 16S rDNA sequence of Rickettsiales DNA from Rh. turanicus ticks showed 100% identity with Ehrlichia canis and unidentified Ehrlichia sp. Obtained sequences of Rickettsiales bacteria were grouped along with their respective species in phylogenetic trees, which were previously reported in Greece, Cuba, Iraq, Turkey, Pakistan, South Korea, and China (mainland and Taiwan). This extensive study explores the wide range of damaging ticks and their corresponding tick-borne bacteria in the area, suggesting a possible danger to both livestock and human communities.

First Molecular Identification of Rickettsia aeschlimannii and Rickettsia africae in Ticks from Ghana

The threats from vector-borne pathogens transmitted by ticks place people (including deployed troops) at increased risk for infection, frequently contributing to undifferentiated febrile illness syndromes. Wild and domesticated animals are critical to the transmission cycle of many tick-borne diseases. Livestock can be infected by ticks, and serve as hosts to tick-borne diseases such as rickettsiosis. Thus, it is necessary to identify the tick species and determine their potential to transmit pathogens. A total of 1,493 adult ticks from three genera-Amblyomma, Hyalomma, and Rhipicephalus-were identified using available morphological keys and were pooled (n = 541) by sex and species. Rickettsia species were detected in 308 of 541 (56.9%) pools by genus-specific quantitative polymerase chain reaction assay (Rick17b). Furthermore, sequencing of the outer membrane protein A and B genes (ompA and ompB) of random samples of Rickettsia-positive samples led to the identification of Rickettsia aeschlimannii and Rickettsia africae with most R. africae DNA (80.2%) detected in pools of Amblyomma variegatum. We report the first molecular detection and identification of the rickettsial pathogens R. africae and R. aeschlimannii in ticks from Ghana. Our findings suggest there is a need to use control measures to prevent infections from occurring among human populations in endemic areas in Ghana. This study underscores the importance of determining which vector-borne pathogens are in circulation in Ghana. Further clinical and prevalence studies are needed to understand more comprehensively the clinical impact of these rickettsial pathogens contributing to human disease and morbidity in Ghana.

Evidence on the prevalence of emerging and re-emerging tick- and flea-borne rickettsial agents in acute encephalitis syndrome endemic areas of northeast Uttar Pradesh, India

Outbreaks of acute encephalitis syndrome (AES) with unknown aetiology are reported every year in Gorakhpur district, Uttar Pradesh, India, and Orientia tsutsugamushi, the rickettsial pathogen, responsible for scrub typhus has been attributed as the primary cause of AES problem. However, information on the prevalence of other rickettsial infections is lacking. Hence, this study was carried out to assess any occurrence of tick- and flea-borne rickettsial agents in villages reporting AES cases in this district. In total, 825 peridomestic small mammals were trapped, by setting 9254 Sherman traps in four villages with a trap success rate of 8.9%. The Asian house shrew, Suncus murinus, constituted the predominant animal species (56.2%) and contributed to the maximum number (87.37%) of ectoparasites. In total, 1552 ectoparasites comprising two species of ticks and one species each of flea and louse were retrieved from the trapped rodents/shrews. Rhipicephalus sanguineus, the brown dog tick, was the predominant species retrieved from the trapped rodents/shrews, and the overall infestation rate was 1.75 per animal. In total, 4428 ectoparasites comprising five tick species, three louse species and one flea species were collected from 1798 domestic animals screened. Rhipicephalus microplus was the predominant tick species collected from the domestic animals. The cat flea, Ctenocephalides felis, constituted 1.5% of the total ectoparasites. Of all the ectoparasite samples (5980) from domestic animals and rodents, tested as 1211 pools through real-time PCR assays, 64 pools were positive for 23S rRNA gene of rickettsial agents. The PCR-positive samples were subjected to multi-locus sequence typing (MLST). In BLAST and phylogenetic analysis, the ectoparasites were found to harbour Rickettsia asembonensis (n = 9), Rickettsia conorii (n = 3), Rickettsia massiliae (n = 29) and Candidatus Rickettsia senegalensis (n = 1). A total of 22 pools were detected to have multiple rickettsial agents. The prevalence of fleas and high abundance of tick vectors with natural infections of rickettsial agents indicates the risk of transmission of tick- and flea-borne rickettsial diseases in rural villages of Gorakhpur. Further epidemiological studies are required to confirm the transmission of these agents to humans.

Serological and molecular epidemiological investigation of Mediterranean spotted fever in Yunnan Province, China

OBJECTIVES

Given the limited research and its potential hazards, the study aimed to determine the prevalence of Mediterranean spotted fever (MSF) caused by Rickettsia conorii (R. conorii), a tick-borne disease, in Yunnan Province, China.

METHODS

Through stratified sampling across five distinct regions in Yunnan, 5358 blood samples were obtained from the general healthy population. Enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), and Polymerase chain reaction (PCR) were employed for analysis.

RESULTS

IFA identified 27 (0.50%) subjects with immunoglobulin G (IgG) positivity; none were positive for immunoglobulin M (IgM) via ELISA. PCR detected one individual with R. conorii outer membrane protein A (ompA). Significant seroprevalence variation was observed, particularly in Southern Yunnan (P = 0.032), with R. conorii subsp. conorii confirmed in the PCR-positive sample.

CONCLUSIONS

This research reveals a correlation between MSF prevalence, geography, and climate in Yunnan. The paucity of prior studies underscores MSF's potential diagnostic challenges in the region. Comprehensive understanding of the pathogen's distribution is pivotal for intervention. Given the study's scope and Yunnan's unique setting, additional research is advocated.

New tick records with notes on rickettsial infection from the wildlife of the state of Espírito Santo, southeastern Brazil

This work aimed to report ticks infesting the wildlife among 15 municipalities of the state of Espírito Santo between 2016 and 2021, within the Atlantic Forest biome of southeastern Brazil. A total of 576 tick specimens (187 males, 56 females, 149 nymphs, and 184 larvae) was collected from 41 species of wild vertebrates (two reptiles, nine mammals, and 30 birds). Ticks were identified by morphological or molecular methods into 18 species, being 12, four, one and one of the genera Amblyomma, Ixodes, Rhipicephalus and Ornithodoros, respectively. Amblyomma rotundatum was the only species collected from reptiles. Ticks collected from mammals were identified as Amblyomma brasiliense, Amblyomma calcaratum, Amblyomma dubitatum, Amblyomma longirostre, Amblyomma nodosum, Amblyomma pacae, Amblyomma sculptum, Amblyomma varium and Rhipicephalus microplus. Amblyomma sculptum was the species found on the widest variety of hosts, collected from four mammal orders and five bird orders. Passeriformes birds were infested by Amblyomma fuscum, A. longirostre (also found on non- passerine birds), A. nodosum, Amblyomma parkeri, Amblyomma romarioi, A. varium and Ixodes loricatus. An adult female of Ixodes rio was collected from a Piciformes bird. Seabirds of the order Procellariiformes were infested by Ixodes percavatus sensu lato and Ixodes uriae. The argasid Ornithodoros capensis was collected from an offshore metallic platform that was used by Suliformes seabirds. Rickettsial agents of the spotted fever group, Rickettsia amblyommatis and Rickettsia sp. strain Pampulha, were detected in the ticks A. longirostre [from the Paraguayan hairy dwarf porcupine (Coendou spinosus)] and A. dubitatum [from the capybara (Hydrochoerus hydrochaeris)], respectively. The following nine tick species are reported for the first time in Espírito Santo state: A. calcaratum, A. fuscum, A. pacae, A. parkeri, A. romarioi, I. loricatus, I. rio, I. uriae, and O. capensis. Although it is also the first report of I. uriae in Brazil, we do not consider it established in the country. Multiple new tick-host associations are reported in the present study.

Distribution of different Rickettsia species in countries of the WHO Eastern Mediterranean (WHO-EMRO) region: An overview

SUBJECT

Rickettsia is a zoonotic bacterial pathogen transmitted by vectors and has extensive reservoirs in animal and human populations. Rickettsiosis is a public health problem all over the world. However, comprehensive information on the geographical distribution of different Rickettsia species, infection status of reservoirs, vectors, and human cases is lacking in most parts of the world. Therefore, this study aimed to investigate the geographical distribution of different Rickettsia species and their vectors in countries of the WHO-EMRO region.

METHODS

In this review study, a search was conducted for reports and published studies on Rickettsia species from WHO-EMRO region countries in various databases from 1995 to 2022. Finally, the reported status of human cases, reservoirs, and vectors associated with each species in different countries was documented.

RESULTS

Reports of infections related to the detection of Rickettsia species were only available for 15 out of 22 WHO-EMRO member countries. A total of twenty-four Rickettsia species, including R. sibrica, R. lusitaniae, R. africae, R. prowazekii, R. felis, R. typhi, R. rickettsii, R. aeschlimannii, R. conorii, R. massiliae, R. helvetica, R. monacensis, R. rhipicephali, R. bellii, R. asembonensis, R. hoogstraalii, R. andeanae, R. raoultii, R. asiatica, R. slovaca, R. australis, R. barbariae, Candidatus R. amblyommii, and Candidatus R. goldwasserii, were reported from WHO-EMRO member countries. Furthermore, human cases infected with six different Rickettsia species, including R. sibrica, R. prowazekii, R. felis, R. typhi, R. rickettsii, R. aeschlimannii, R. conorii, R. massiliae, and R. helvetica, were reported from these countries.

CONCLUSION

The vast diversity of Rickettsia vectors has contributed to the ongoing discovery of new Rickettsia species. Therefore, further research on the reservoir hosts of Rickettsia infections in the understudied WHO-EMRO region is crucial. This research sheds light on Rickettsia disease's epidemiology and transmission dynamics in this region.

Seasonal pattern of questing ticks and prevalence of pathogenic Rickettsia and Anaplasmataceae in Khao Yai national park, Thailand

BACKGROUND

Tick-borne diseases (TBD) are considered neglected diseases in Thailand with disease burden likely underestimated. To assess risk for emerging TBD in Thailand, the seasonality of questing tick and pathogen prevalence were studied in Khao Yai National Park, a top tourist destination.

METHODS

During 2019, questing ticks around tourist attractions were systematically collected bimonthly and analyzed for Rickettsia and Anaplasmataceae bacterial species by polymerase chain reaction and DNA sequencing.

RESULTS

Larvae and nymphs of questing ticks peaked in Khao Yai National Park during the late rainy-winter season, though no specific trends were observed in adult ticks. Winter (November to February) was the highest risk for human tick-bites due to higher numbers of both ticks and visitors. Of the total 5916 ticks analyzed (651 pools), Anaplasma phagocytophilum, Neoehrlichia mikurensis, Ehrlichia ewingii, and Ehrlichia chaffeensis were detected at low rates (≤0.05%). There was a higher prevalence of human rickettsioses (0.2-7%) in ticks surveyed with Rickettsia tamurae, Rickettsia raoultii, and Rickettsia montana the major species. Amblyomma ticks had the highest prevalence of Rickettsia (85%, 35/44 Amblyomma adults), in which only R. tamurae and R. raoultii were found in Amblyomma with mixed species infections common. We report the first detection of R. africae-like and N. mikurensis in Ixodes granulatus adults in Thailand, suggesting I. granulatus as a potential vector for these pathogens.

CONCLUSION

This study demonstrated the risk of emerging TBD in Thailand and underscores the need for tick-bite prevention among tourists in Thailand.

Pathogenic Rickettsia spp. as emerging models for bacterial biology

Our understanding of free-living bacterial models like Escherichia coli far outpaces that of obligate intracellular bacteria, which cannot be cultured axenically. All obligate intracellular bacteria are host-associated, and many cause serious human diseases. Their constant exposure to the distinct biochemical niche of the host has driven the evolution of numerous specialized bacteriological and genetic adaptations, as well as innovative molecular mechanisms of infection. Here, we review the history and use of pathogenic Rickettsia species, which cause an array of vector-borne vascular illnesses, as model systems to probe microbial biology. Although many challenges remain in our studies of these organisms, the rich pathogenic and biological diversity of Rickettsia spp. constitutes a unique backdrop to investigate how microbes survive and thrive in host and vector cells. We take a bacterial-focused perspective and highlight emerging insights that relate to new host-pathogen interactions, bacterial physiology, and evolution. The transformation of Rickettsia spp. from pathogens to models demonstrates how recalcitrant microbes may be leveraged in the lab to tap unmined bacterial diversity for new discoveries. Rickettsia spp. hold great promise as model systems not only to understand other obligate intracellular pathogens but also to discover new biology across and beyond bacteria.

Molecular surveillance of microbial agents from cattle-attached and questing ticks from livestock agroecosystems of Antioquia, Colombia

Ticks are obligate ectoparasites and vectors of pathogens affecting health, agriculture, and animal welfare. This study collected ticks from the cattle and questing ticks of 24 Magdalena Medio Antioquia region cattle farms. Genomic DNA was extracted from the specimens (individual or pools) of the 2088 adult ticks collected from cattle and 4667 immature questing ticks collected from pastures. The molecular detection of Babesia, Anaplasma, Coxiella and Rickettsia genera was performed by polymerase chain reaction amplification and subsequent DNA sequencing. In a total of 6755 Rhipicephalus microplus DNA samples, Anaplasma marginale was the most detected with a frequency of 2% (Confidence Interval- CI 1.68-2.36), followed by Babesia bigemina with 0.28% (CI 0.16-0.44), Coxiella spp. with 0.15% (CI 0.07-0.27), and Rickettsia spp. with 0.13% (CI 0.06-0.25). Molecular analysis of the DNA sequences obtained from the tick samples revealed the presence of Coxiella-like endosymbiont and R. felis. These results demonstrated the diversity of microorganisms present in R. microplus ticks predominantly associated with cattle and questing ticks from livestock agroecosystems, suggesting their role as reservoirs and potential biological vectors of these microorganisms on the studied sites. Also, it emphasizes the need to combine acarological surveillance with clinical diagnoses and control strategies on regional and national levels.

Human Tick-Borne Diseases and Advances in Anti-Tick Vaccine Approaches: A Comprehensive Review

This comprehensive review explores the field of anti-tick vaccines, addressing their significance in combating tick-borne diseases of public health concern. The main objectives are to provide a brief epidemiology of diseases affecting humans and a thorough understanding of tick biology, traditional tick control methods, the development and mechanisms of anti-tick vaccines, their efficacy in field applications, associated challenges, and future prospects. Tick-borne diseases (TBDs) pose a significant and escalating threat to global health and the livestock industries due to the widespread distribution of ticks and the multitude of pathogens they transmit. Traditional tick control methods, such as acaricides and repellents, have limitations, including environmental concerns and the emergence of tick resistance. Anti-tick vaccines offer a promising alternative by targeting specific tick proteins crucial for feeding and pathogen transmission. Developing vaccines with antigens based on these essential proteins is likely to disrupt these processes. Indeed, anti-tick vaccines have shown efficacy in laboratory and field trials successfully implemented in livestock, reducing the prevalence of TBDs. However, some challenges still remain, including vaccine efficacy on different hosts, polymorphisms in ticks of the same species, and the economic considerations of adopting large-scale vaccine strategies. Emerging technologies and approaches hold promise for improving anti-tick vaccine development and expanding their impact on public health and agriculture.

Development and validation of a novel detection method for Rickettsia rickettsii using a loop-mediated isothermal amplification assay

Introduction

Rickettsia rickettsii is an obligate, intracellular pathogen and the causative agent of Rocky Mountain spotted fever (RMSF). RMSF is an important zoonotic disease due to its high fatal outcome in humans. The difficulty of clinical diagnosis due to the low sensitivity and specificity of current diagnostic methods are a principal setback. We reported the development of a new method for the detection of R. rickettsii in human and tick DNA samples using loop-mediated isothermal amplification (LAMP), as well as the validation of the LAMP test for R. rickettsii in field samples of infected ticks and humans, determining the diagnostic sensitivity and specificity, as well as the reproducibility of the test.

Methods

This technique uses hydroxy naphthol blue (HNB) as an indicator of the formation of magnesium pyrophosphate, a marker for the presence of DNA. Here, we used a putative R. rickettsii gene as a target for three pairs of primers that specifically amplify R. rickettsii DNA by hairpin-based isothermal amplification technique (LAMP).

Results and discussion

The sensitivity of the assay was ~1.6-3 pg, which is 10 times more sensitive than PCR. To determine the diagnostics specificity and sensitivity, 103 human DNA samples and 30 tick DNA samples were evaluated. For the human samples, a sensitivity for HNB of 93%, a specificity of 70% and a k of 0.53 were obtained. For electrophoresis the sensitivity was 97% with a specificity of 58% and a k of 0.42. For tick samples, a sensitivity of 80% was obtained, a specificity of 93% for HNB and for electrophoresis the sensitivity and specificity were 87%. The k for both was 0.73. The degree of concordance between HNB and electrophoresis was 0.82 for humans and for ticks, it was 0.87. The result is obtained in shorter time, compared to a PCR protocol, and is visually interpreted by the color change. Therefore, this method could be a reliable tool for the early diagnosis of rickettsiosis.

Eco-epidemiological study of seropositivity against Rickettsia and Leptospira agents in rural areas of Urabá, Colombia

Rickettsioses and leptospirosis are infectious diseases that are often underdiagnosed due to a lack of knowledge about their epidemiology, pathophysiology, diagnosis, management, among others.

Objetive

to characterize the seroprevalence and seroincidence of both Rickettsia and Leptospira agents and determine the risk factors for these outcomes in rural areas of Urabá, Antioquia.

Methods

a secondary data analysis using information on Rickettsia and Leptospira exposure from a prior prospective study that explored sociocultural and ecological aspects of Rickettsia infection in rural Urabá, Colombia. A multinomial mixed logistic regression model was employed to analyze factors linked to seroprevalent cases of Rickettsia, Leptospira and both, along with descriptive analyses of seroincident cases.

Results

the concomitant seroprevalence against Rickettsiaand Leptospira was 9.38% [95%CI 6.08%-13.37%] (56/597). The factors associated with this seroprevalence were age (ORa= 1.02 [95%CI 1.007-1.03]), male gender (ORa= 3.06 [95%CI 1.75-5.37]), fever history (ORa= 1.71 [95%CI 1.06-2.77]) the presence of breeding pigs (ORa= 2.29 [95%CI 1.36-3.88]), peridomicile yucca crops(ORa= 2.5 [95%CI 1.1-5.62]), and deforestation practices(ORa= 1.74 [95%CI 1.06-2.87]). The concomitant seroincidence against Rickettsia and Leptospira was 1.09% (3/274) [95%CI 0.29%-4.05%], three cases were female, with a median age of 31.83 years-old (IQR 8.69-56.99). At the household level, all the seroincident cases had households built partially or totally with soil floors, wooden walls, and zinc roofs. Two seroincident cases described the presence of equines, canines, and domestic chickens in intra or peri-domicile. Finally, two cases were exposed to synanthropic rodents, and one case to tick infestation.

Conclusion

there is evidence of seroprevalent and seroincident cases of seropositivity against both Rickettsia and Leptospira in rural areas of Urabá, Colombia. These findings can help improve public health surveillance systems in preventing, detecting, and attending to the different clinical cases caused by these pathogens.

Tick-borne microorganisms in Amblyomma tigrinum (Acari: Ixodidae) from the Patagonian region of Argentina

This study presents the results of the molecular detection of tick-borne microorganisms in Amblyomma tigrinum Koch collected near the city of Viedma, Río Negro, Argentina. Ticks were collected in their non-parasitic stage, on pet dogs and on Lycalopex gymnocercus (Pampa fox). Also, six tick samples from humans were analyzed. All ticks were morphologically identified to species level and genomic DNA was extracted. The DNA samples were examined by end point PCR assays to amplified DNA of Anaplasma sp., Babesia sp., Ehrlichia sp., Rickettsia sp. and Theileria sp. Although all tested DNA samples from the collected ticks resulted negative to the detection of Piroplasmida and Rickettsia spp., 16 samples (16.5%, including all hosts) were positive in the 16S rDNA gene PCR that detects bacteria from the Anaplasmataceae family. Phylogenetic analysis of seven obtained partial sequences resulted in the identification of three bacteria: two Ehrlichia spp. (related to Ehrlichia sp. strain Iberá and strain Viedma) and Candidatus Anaplasma boleense. The latter finding represents the first detection of this novel Candidatus species in A. tigrinum. Based on the results of this study, it must be assumed that the diversity of bacteria of the Anaplasmataceae family in Argentina is greater than previously thought, and that these bacteria can infect a wide range of domestic and wild animals.

Clinical and laboratory features of rickettsioses in Yucatan, Mexico

Rickettsia species are obligate intracellular bacteria that can cause mild to severe human disease. Based on phylogeny, clinical symptoms, and antigenic properties, rickettsiae are classified into four groups. Infections by these agents are characterized by clinical symptoms ranging from self-limited to severe and even fatal febrile illnesses, depending on the Rickettsia spp. involved, the patient's predisposition, and timely medical care. The present study aimed to characterize rickettsial diseases in Yucatan according to clinical and laboratory features appearing in medical records corresponding to 427 samples taken between 2015 and 2018. A study was conducted over the period 2015-2018 on 427 samples. Clinical and laboratory features were documented from the patients' medical records. For molecular diagnosis, blood was collected in 3.8 % sodium citrate as anticoagulant, and DNA was extracted. Single-step and nested PCR amplification was performed using genus-specific primers for the rickettsial 17kDa and ompB genes. The amplicons obtained were purified and sequenced. A total of 22.7 % (97/427) positive cases of Rickettsia spp. were identified by PCR from 14.15 % (15/106) of the municipalities in Yucatan. 75.2 % (73/97) of the cases were from the city of Merida during the autumn (September-December). The age groups with the highest frequency of confirmed cases were pediatric (5-14 years) (57.7 %) and adults (25-49 years) (42.2 %). There were six fatal cases in children, one associated with R. typhi and five with R. rickettsii. In non-fatal cases, 32.9 % (32/97) corresponded to the spotted fever group (SFG), and 60.8 % (59/97) to the typhus group (TG). Significant differences in signs, and laboratory data, were observed between the pediatric and adult populations. For the treatment of patients, oral and intravenous doxycycline was used in severe hospitalized cases. Typhus group and spotted fever group Rickettsiae are endemic pathological agents found in urban and rural areas of our region. Molecular identification allows for greater diagnostic accuracy and timely treatment and consequently a better prognosis. It is necessary to implement or reinforce measures focused on the dissemination of knowledge regarding rickettsial diseases and their prevention.