Tick-borne Diseases Research Articles

Impact of E. muris infection on B. burgdorferi-induced joint pathology in mice.

Tick-borne infections are increasing in the United States and around the world. The most common tick-borne disease in the United States is Lyme disease caused by infection with the spirochete Borrelia burgdorferi (Bb), and pathogenesis varies from subclinical to severe. Bb infection is transmitted by Ixodes ticks, which can carry multiple other microbial pathogens, including Ehrlichia species. To address how the simultaneous inoculation of a distinct pathogen impacted the course of Bb-induced disease, we used C57BL/6 (B6) mice which are susceptible to Bb infection but develop only mild joint pathology. While infection of B6 mice with Bb alone resulted in minimal inflammatory responses, mice co-infected with both Bb and the obligate intracellular pathogen Ehrlichia muris (Em) displayed hematologic changes, inflammatory cytokine production, and emergency myelopoiesis similar to what was observed in mice infected only with Em. Moreover, infection of B6 mice with Bb alone resulted in no detectable joint inflammation, whereas mice co-infected with both Em and Bb exhibited significant inflammation of the ankle joint. Our findings support the concept that co-infection with Ehrlichia can exacerbate inflammation, resulting in more severe Bb-induced disease.

Comparative evaluation of real-time polymerase chain reaction, conventional PCR and microscopy for detection of Babesia bigemina in bovines of Punjab (India).

Babesia bigemina is a major cause of bovine babesiosis, an economically devastating tick-borne disease that needs timely diagnosis for precise treatment. In present investigation, the detection efficacy of real-time PCR (qPCR) in comparison to conventional PCR and microscopy targeting 18S ribosomal gene was evaluated on 95 bovines (70 cattle and 25 buffaloes) suspected for babesiosis. Real-time PCR was standardized with the 10-fold serial dilutions in duplication of the given positive control (2 × 106 copy number) ranging from 106 to 100 copy number/µL and mean Ct value of each dilution was taken to extrapolate the curve. The samples with Ct value 36.92 of 10 copy number/µL were considered as positive. Out of 95 samples, 5 (5.26%), 21 (22.10%) and 49 (51.58%) positive by microscopy, conventional PCR and real-time PCR were in corresponding range of > 106-104, 104-103, and 103-<10 copy number/µL, respectively. The concordance of real-time PCR with conventional PCR and microscopy was moderate (Kappa = 0.523) and slight (Kappa = 0.09), respectively. The cows were at four times risk than the buffaloes for B. bigemina infection (Odds ratio:3.85, CI:1.4255-10.4370). This pioneer report from Punjab state (India) of application of real-time PCR to detect B. bigemina in bovines was found to be more sensitive than conventional PCR and microscopy that needs further investigations on a greater number of random samples.

Tick-Borne Diseases in Sub-Saharan Africa: A Systematic Review of Pathogens, Research Focus, and Implications for Public Health.

Sub-Saharan Africa, with its hot and humid climate, is a conducive zone for tick proliferation. These vectors pose a major challenge to both animal and human health in the region. However, despite the relevance of emerging diseases and evidence of tick-borne disease emergence, very few studies have been dedicated to investigating zoonotic pathogens transmitted by ticks in this area. To raise awareness of the risks of tick-borne zoonotic diseases in sub-Saharan Africa, and to define a direction for future research, this systematic review considers the trends of research on tick-borne bacteria, parasites, and viruses from 2012 to 2023, aiming to highlight the circulation of these pathogens in ticks, cattle, sheep, goats, and humans. For this purpose, three international databases were screened to select 159 papers fitting designed inclusion criteria and used for qualitative analyses. Analysis of these studies revealed a high diversity of tick-borne pathogens in sub-Saharan Africa, with a total of 37 bacterial species, 27 parasite species, and 14 viruses identified. Among these, 27% were zoonotic pathogens, yet only 11 studies investigated their presence in humans. Furthermore, there is growing interest in the investigation of bacteria and parasites in both ticks and ruminants. However, research into viruses is limited and has only received notable interest from 2021 onwards. While studies on the detection of bacteria, including those of medical interest, have focused on ticks, little consideration has been given to these vectors in studies of parasites circulation. Regarding the limited focus on zoonotic pathogens transmitted by ticks, particularly in humans, despite documented cases of emerging zoonoses and the notable 27% proportion reported, further efforts should be made to fill these gaps. Future studies should prioritize the investigation of zoonotic pathogens, especially viruses, which represent the primary emerging threats, by adopting a One Health approach. This will enhance the understanding of their circulation and impact on both human and animal health. In addition, more attention should be given to the risk factors/drivers associated to their emergence as well as the perception of the population at risk of infection from these zoonotic pathogens.

Evaluation of the relationship between YKL-40 level and clinical severity in patients with Crimean-Congo hemorrhagic fever

ABSTRACT Crimean-Congo hemorrhagic fever (CCHF) is a widespread tick-borne viral disease. YKL-40 (also known as chitinase-3-like-1 protein) is an acute phase protein released by various immune cells. The purpose of this study was to investigate the relationship between YKL-40 level and the clinical course and prognosis of CCHF. The study included 78 patients who were admitted to our hospital between April 15 and 30 August 2022 and had a positive polymerase chain reaction test result for CCHF. The patients were divided into two groups, severe and non-severe. In addition, a control group consisting of 22 healthy people was established. Mean serum YKL-40 levels were significantly higher in patients than controls (106.8 ng/mL ± 91.2 and 47.1 ng/mL ± 35.3, respectively; p < 0.001). However, mean YKL-40 levels were also significantly higher in patients with severe CCHF compared to non-severe cases (173.3 ± 112.3 and 67.5 ± 41.7, respectively; p < 0.001). A comparison of the 10 exitus patients and the 68 survivors revealed significantly higher YKL-40 levels in the exitus group (mean: 214.0 ± 139.0 and 92.8 ± 73.6, respectively; p = 0.001). A receiver operating characteristic analysis for YKL-40 levels to distinguish between severe and non-severe patients found an area under the curve of 0.925. YKL-40 levels were measured with a sensitivity of 97% and a specificity of 84% with a cutoff value of 90.7 ng/mL. YKL-40 levels measured at the time of hospital presentation in patients with CCHF can be used as a biomarker for clinical course and prognosis.

Tickborne disease contributing to lamb deaths across Scotland.

Tickborne disease contributing to lamb deaths across Scotland.

Candidatus Midichloria mitochondrii can be vertically transmitted in Hyalomma anatolicum

In this study, a tick intracellular symbiont, Candidatus Midichloria mitochondrii, was detected in Hyalomma anatolicum from Xinjiang, China. Morphological identification and cytochrome oxidase subunit I sequence alignment were used for molecular identification of the tick species. PCR detection further revealed the presence of endosymbiont C. M. mitochondrii in the tick. Specific primers were designed for Groel and 16S rRNA genes of C. M. mitochondrii for PCR amplification and phylogenetic analysis. To further investigate the vertical transmission characteristics of C. M. mitochondrii, specific primers were designed based on the FabⅠ gene fragment to detect C. M. mitochondrii in different developmental stages and organs of the tick using qPCR. Of the 336 tick specimens collected from the field, 266 samples were identified as H. anatolicum on the basis of morphological characteristics. The gene fragment alignment results of COI confirmed that these ticks were H. anatolicum. The phylogenetic analysis showed that Groel gene of C. M. mitochondrii clustered with Midichloria strains detected in Ixodes ricinus ticks from Italy and Ixodes holocyclus ticks from Australia, with 100% sequence similarity. Furthermore, the 16S rRNA gene of C. M. mitochondrii clusters with the strains isolated from Hyalomma rufipes ticks in Italy, exhibiting the highest degree of homology. qPCR results showed that C. M. mitochondrii was present at all developmental stages of H. anatolicum, with the highest relative abundance in eggs, and lower relative abundance in nymphs and unfed males. With female tick blood feeding, the relative abundance of C. M. mitochondrii increased, and a particularly high relative abundance was detected in the ovaries of engorged female ticks. This study provides information for studying the survival adaptability of H. anatolicum, and provides data for further investigation of the mechanisms regulating tick endosymbionts in ticks, enriching the reference materials for comprehensive prevention and control of tick-borne diseases.

Hyalomma marginatum - an emerging tickborne disease vector for the UK?

The tick Hyalomma marginatum is expanding its geographical range, reinforcing the need for surveillance and control to prevent the emergence of tickborne equine disease. Daniel Armstrong, policy adviser for exotic animal diseases at Defra, explains more.

Ticks and Tick-Borne Pathogens: Occurrence and Host Associations over Four Years of Wildlife Surveillance in the Liguria Region (Northwest Italy).

Tick-borne diseases (TBDs) are a considerable public health problem worldwide. The occurrence of Anaplasma spp., Borrelia burgdorferi s.l., Coxiella burnetii, Rickettsia spp., and tick-borne encephalitis virus (TBEv) was investigated via PCR and sequencing in 683 ticks collected from 105 roe deer, 61 wild boars, 49 fallow deer, and 2 chamois, in the Liguria region, northwest Italy, between 2019 and 2022. The ticks were morphologically identified. Four different tick species were found: Ixodes ricinus (66.8% of the collected ticks), Dermacentor marginatus (15.8%), Rhipicephalus sanguineus s.s. (15.7%), and Haemaphysalis punctata (0.9%). Six ticks (0.9%) were only identified as Rhipicephalus spp. Of the 222 pools analyzed, 27.9% were positive. Most pools (n = 58, 26.1% of pools analyzed) were positive for Rickettsia spp., and several species were found: Rickettsia slovaca was the dominant species (15.3%), followed by R. monacensis (8.1%), while R. helvetica (1.8%), R. massiliae (0.5%), and R. raoultii (0.5%) were found only sporadically. Anaplasma phagocytophilum was identified in three pools and B. burgdorferi s.l. in one pool. All samples were negative for C. burnetii and TBEv. Significant associations were found between I. ricinus and roe deer, D. marginatus and wild boar, and between R. monacensis and I. ricinus. The prevalence of Rickettsia spp. differed significantly between tick and host species. This updated picture of tick species and TBPs in wild ungulates in Liguria, where the population of these animals is increasing, shows a widespread presence of potentially zoonotic Rickettsia spp. Continuous monitoring and public information on preventive measures are needed.

Assessment of Novel Haematological Inflammatory Markers (NLR, SII, and SIRI) as Predictors of SIRS in Dogs with Canine Monocytic Ehrlichiosis

Canine monocytic ehrlichiosis (CME) is a tick-borne and fatal disease that induces a systemic inflammatory response syndrome (SIRS), which underscores the importance of assessing the level of inflammation. In this study, we aimed to evaluate changes in the SII and SIRI indexes in dogs with CME based on the presence of SIRS criteria. A total of 53 dogs affected with CME and 13 healthy dogs were included in the study. Haematological data, including neutrophil to lymphocyte ratio (NLR), systemic inflammatory index (SII), and systemic inflammatory response index (SIRI), were collected and statistically compared between groups based on SIRS status. The NLR and SIRI indexes were significantly higher in dogs with CME that meet the criteria for SIRS compared to dogs without SIRS and healthy controls. In summary, monitoring the SIRI index can aid in evaluating SIRS criteria in dogs with CME, which can help improve their treatment and overall prognosis.

Risk of Ixodes ricinus Bites in a Population of Forestry Workers in an Endemic Region in France.

The progressing worldwide increases in tick occurrence and tick-borne diseases calls for the development of new prevention strategies to reduce their impact on human and animal health. Defining the risk of exposure to tick bites is therefore essential. Forestry workers are at high risk of tick bites. We set up an explorative study among forestry workers in the Alsace region in eastern France to measure the different factors affecting the risk of Ixodes ricinus tick bites during their activities in forests. For one year, forestry workers recorded the presence of ticks on their clothes and tick bites every time they were working in teams in different forest ecosystems. Questions about the prevention measures they followed were also noted. Among the 32 participants, we were able to differentiate between groups having a high, neutral, or low risk of being bitten. The median tick bite number per year was 4 (0-8). We tried to identify individual as well as environmental factors affecting the risk of tick bites. Factors influencing the risk were the seasonal peak of tick activity in May and June, the time of exposure, and the forest ecosystems visited during the year. Additional factors potentially affecting the risk were also identified.

Natural selection and recombination at host-interacting lipoprotein loci drive genome diversification of Lyme disease and related bacteria.

Lyme disease (also called Lyme borreliosis in Europe), a condition caused by spirochete bacteria of the genus Borrelia, transmitted by hard-bodied Ixodes ticks, is currently the most prevalent and rapidly expanding tick-borne disease in the United States and Europe. Borrelia interspecies and intraspecies genome comparisons of Lyme disease-related bacteria are essential to reconstruct their evolutionary origins, track epidemiological spread, identify molecular mechanisms of human pathogenicity, and design molecular and ecological approaches to disease prevention, diagnosis, and treatment. These Lyme disease-associated bacteria harbor complex genomes that encode many genes that do not have homologs in other organisms and are distributed across multiple linear and circular plasmids. The functional significance of most of the plasmid-borne genes and the multipartite genome organization itself remains unknown. Here we sequenced, assembled, and analyzed whole genomes of 47 Borrelia isolates from around the world, including multiple isolates of the human pathogenic species. Our analysis elucidates the evolutionary origins, historical migration, and sources of genomic variability of these clinically important pathogens. We have developed web-based software tools (BorreliaBase.org) to facilitate dissemination and continued comparative analysis of Borrelia genomes to identify determinants of human pathogenicity.

New insights in the diagnosis and treatment of equine piroplasmosis: pitfalls, idiosyncrasies, and myths.

Equine piroplasmosis (EP) is a global tick-borne disease of equids caused by the intraerythrocytic apicomplexan parasites Theileria equi and Babesia caballi, and the more recently discovered Theileria haneyi. These parasites can be transmitted by several tick species, including Dermacentor, Hyalomma, and Rhipicephalus, but iatrogenic and vertical transmission are also common. Clinical signs of EP include poor performance, fever, icterus, abortions, among others, and peracute or acute forms of infection are associated with high mortality in non-endemic areas. EP is a reportable disease and represents an important barrier for the international trade of horses and other equids, causing disruption of international equine sports. Tick control measures, serological and molecular diagnostic methods, and parasiticidal drugs are currently used against EP, while vaccines remain unavailable. Since most acaricides used in equids are non-environmentally friendly and linked to drug resistances, this is considered as an unsustainable approach. Imidocarb dipropionate (ID) and buparvaquone (BPQ) are currently the main drugs used to control the disease. However, while ID has several side and toxic effects and recurrent failures of treatment have been reported, BPQ is less effective in the clearance of T. equi infection and not available in some countries. Thus, novel alternative and effective therapeutics are needed. While current trade regulations require testing equids for EP before exportation, the lack of standardized PCR tests and limitations of the currently recommended serological assays entail a risk of inaccurate diagnosis. Hereby, we propose a combination of standardized PCR-based techniques and improved serological tests to diminish the risks of exporting EP-infected animals making equid international trade safer. In addition, this review discusses, based on scientific evidence, several idiosyncrasies, pitfalls and myths associated with EP, and identifies weaknesses of current methods of control and gaps of research, as initial steps toward developing novel strategies leading to control this disease.

Navigating the Landscape of Tick Diversity: Integrating Molecular Approaches for Enhanced Control Measures.

The emergence and spread of infectious diseases, particularly zoonotic diseases originating from wildlife, pose significant threats to global health and economy. This review examines the pivotal role of ticks as vectors in transmitting pathogens to humans, livestock, and wildlife and the use of molecular techniques in their identification. Tick infestations result in economic losses through reduced animal productivity, anemia, and quality deterioration of hides. Furthermore, ticks serve as reservoirs for a wide range of pathogens including viruses, bacteria, fungi, protozoa, and nematodes, contributing to the transmission of diseases such as Crimean-Congo hemorrhagic fever, tick-borne encephalitis, and African swine fever among others. The interface between wildlife, livestock, and humans facilitates the transmission of zoonotic pathogens, exacerbated by nomadic and pastoralist lifestyles that promote interactions between wildlife and domestic animals. This movement of animals across landscapes enhances the dispersion of tick vectors, increasing the risk of pathogen exposure for diverse populations. Historically, tick identification in sub-Saharan Africa has relied on morphological characteristics despite limitations such as species overlap and variability. Molecular techniques offer a more precise means of species identification, providing critical data for effective tick and pathogen management strategies. Integrating molecular approaches into tick research enhances our understanding of tick diversity, distribution patterns, and pathogen dynamics. This knowledge is essential for developing targeted interventions to mitigate the impact of tick-borne diseases on public and veterinary health worldwide.

Co-infection dynamics of B. afzelii and TBEV in C3H mice: insights and implications for future research.

Ticks are important vectors of disease, particularly in the context of One Health, where tick-borne diseases (TBDs) are increasingly prevalent worldwide. TBDs often involve co-infections, where multiple pathogens co-exist in a single host. Patients with chronic Lyme disease often have co-infections with other bacteria or parasites. This study aimed to create a co-infection model with Borrelia afzelii and tick-borne encephalitis virus (TBEV) in C3H mice and to evaluate symptoms, mortality, and pathogen level compared to single infections. Successful co-infection of C3H mice with B. afzelii and TBEV was achieved. Outcomes varied, depending on the timing of infection. When TBEV infection followed B. afzelii infection by 9 days, TBEV symptoms worsened and virus levels increased. Conversely, mice infected 21 days apart with TBEV showed milder symptoms and lower mortality. Simultaneous infection resulted in mild symptoms and no deaths. However, our model did not effectively infect ticks with TBEV, possibly due to suboptimal dosing, highlighting the challenges of replicating natural conditions. Understanding the consequences of co-infection is crucial, given the increasing prevalence of TBD. Co-infected individuals may experience exacerbated symptoms, highlighting the need for a comprehensive understanding through refined animal models. This study advances knowledge of TBD and highlights the importance of exploring co-infection dynamics in host-pathogen interactions.

Pathogen and Host Associations of Soft Ticks Collected in South Texas.

Background: Soft ticks (Family: Argasidae) are vectors of relapsing fever Borrelia in the United States and are potential vectors of African swine fever virus, a pathogen that could have a devastating effect on the U.S. swine industry if introduced to the U.S. mainland. Much of the tick-borne disease research in the U.S. focuses on hard ticks, and less is known about the ecology of soft ticks. Some soft tick species found in the southern U.S. have a wide host range and may feed on cattle, swine, native and exotic ungulates, small mammals, reptiles, and humans. Because the feeding habit of most soft tick species involves taking short, repeated blood meals that may include multiple host species, pathogen transmission among hosts is a concern both for human and animal health. Materials and Methods: Sampling was carried out at four locations in south Texas using dry ice traps placed in or near animal burrows and other sheltering cracks and crevasses that may provide refuge for soft ticks. Collected ticks were identified and subsequently screened for Rickettsia and Borrelia species and for host bloodmeal detection using conventional polymerase chain reaction and Sanger sequencing for pathogen and host species identification. Results: In total, 256 ticks of two Ornithodorinae species were screened. Borrelia species were identified in three samples. Bloodmeal detections were made in 22 tick specimens, representing eight vertebrate host species. Conclusions: Results demonstrate that the soft tick species detected herein feed on a range of wildlife hosts in south Texas and are associated with agents of human disease.

The detection of zoonotic microorganisms in Rhipicephalus sanguineus (brown dog ticks) from Vietnam and the frequency of tick infestations in owned dogs.

Dog owners are greatly concerned about tick infestations in their pets. The prevalence and dispersion of ticks and their disease-causing microorganisms have been limited from the viewpoint of dog owners in Vietnam. This study investigated the presence of tick infestation and the pathogens associated with it in canines that were brought to veterinary hospitals in Vietnam. In the survey, 1,423 dogs participated from February to October 2022. Molecular and morphological methods were utilized to identify ticks and the associated pathogens. In addition,risk variables linked to tick infestation were documented and analyzed using statistical methods. The total exposure to the brown dog tick (Rhipicephalus sanguineus sensu lato) was 29.01%. Nam Dinh has the highest tick prevalence among the research areas. Tick infestation reached its highest point between June and September in the northern region of the country, with distinct seasons showing a strong correlation with tick infestation in dogs. Out of 177 tick pools examined, 146(82.49%) tested positive for at least one infection. Mycoplasma spp. (78.53%) was the most common, followed by Anaplasma spp. (37.29%), Rickettsia felis (5.08%), Babesia vogeli, and Hepatozoon canis (2.82%). In the current study, there was a statistically significant link between tick infestation and characteristics such as age, breed, body size, lifestyle, and bathing frequency. Understanding the seasonal behavior of vector ticks is crucial for identifying individuals or animals susceptible to tick-borne diseases. Studying the distribution of ticks and their ability to carry and disseminate zoonotic germs in specific places could assist veterinarians and policymakers in implementing effective strategies to manage zoonotic infections.

Modeling platform to assess the effectiveness of single and integrated Ixodes scapularis tick control methods

BackgroundLyme disease continues to expand in Canada and the USA and no single intervention is likely to curb the epidemic.MethodsWe propose a platform to quantitatively assess the effectiveness of a subset of Ixodes scapularis tick management approaches. The platform allows us to assess the impact of different control treatments, conducted either individually (single interventions) or in combination (combined efforts), with varying timings and durations. Interventions include three low environmental toxicity measures in differing combinations, namely reductions in white-tailed deer (Odocoileus virginianus) populations, broadcast area-application of the entomopathogenic fungus Metarhizium anisopliae, and fipronil-based rodent-targeted bait boxes. To assess the impact of these control efforts, we calibrated a process-based mathematical model to data collected from residential properties in the town of Redding, southwestern Connecticut, where an integrated tick management program to reduce I.xodes scapularis nymphs was conducted from 2013 through 2016. We estimated parameters mechanistically for each of the three treatments, simulated multiple combinations and timings of interventions, and computed the resulting percent reduction of the nymphal peak and of the area under the phenology curve.ResultsSimulation outputs suggest that the three-treatment combination and the bait boxes–deer reduction combination had the overall highest impacts on suppressing I. scapularis nymphs. All (single or combined) interventions were more efficacious when implemented for a higher number of years. When implemented for at least 4 years, most interventions (except the single application of the entomopathogenic fungus) were predicted to strongly reduce the nymphal peak compared with the no intervention scenario. Finally, we determined the optimal period to apply the entomopathogenic fungus in residential yards, depending on the number of applications.ConclusionsComputer simulation is a powerful tool to identify the optimal deployment of individual and combined tick management approaches, which can synergistically contribute to short-to-long-term, costeffective, and sustainable control of tick-borne diseases in integrated tick management (ITM) interventions.Graphical

Molecular Detection of Theileria ovis, Anaplasma ovis, and Rickettsia spp. in Rhipicephalus turanicus and Hyalomma anatolicum Collected from Sheep in Southern Xinjiang, China.

The Xinjiang Uygur Autonomous Region (Xinjiang) borders eight countries and has a complex geographic environment. There are almost 45.696 million herded sheep in Xinjiang, which occupies 13.80% of China's sheep farming industry. However, there is a scarcity of reports investigating the role of sheep or ticks in Xinjiang in transmitting tick-borne diseases (TBDs). A total of 894 ticks (298 tick pools) were collected from sheep in southern Xinjiang. Out of the 298 tick pools investigated in this study, Rhipicephalus turanicus (Rh. turanicus) and Hyalomma anatolicum (H. anatolicum) were identified through morphological and molecular sequencing. In the southern part of Xinjiang, 142 (47.65%), 86 (28.86%), and 60 (20.13%) tick pools were positive for Rickettsia spp., Theileria spp., and Anaplasma spp., respectively. Interestingly, the infection rate of Rickettsia spp. (73%, 35.10%, and 28.56-41.64%) was higher in Rh. turanicus pools than in H. anatolicum pools (4%, 4.44%, and 0.10-8.79%) in this study. Fifty-one tick pools were found to harbor two pathogens, while nineteen tick pools were detected to have the three pathogens. Our findings indicate the presence of Rickettsia spp., Theileria spp., and Anaplasma spp. potentially transmitted by H. anatolicum and Rh. turanicus in sheep in southern Xinjiang, China.

Japanese spotted fever in an area endemic to SFTS virus: Case report and review of the literature.

The geographic spread of Japanese spotted fever (JSF) in China is gradually expanding, particularly in regions where severe fever with thrombocytopenia syndrome (SFTS) is highly prevalent, with both diseases sharing similarities in epidemiology and clinical presentation. The microbiological diagnosis of JSF is challenging, compounded by low awareness among healthcare professionals in newly affected areas. Moreover, primary healthcare facilities without polymerase chain reaction (PCR) testing capabilities for SFTS often misdiagnose JSF as SFTS. All 3 patients had a history of working in the fields, with cold like symptoms in the early fever stages, but the fever did not improve after a few days. The accompanying symptoms were also very different. Physical examination revealed enlarged lymph nodes, different forms of rash, with or without eschar. Laboratory tests showed thrombocytopenia, eosinophilia, elevated lactate dehydrogenase, and transaminase, with 1 patient experiencing renal damage. It is worth noting that these 3 patients reside in an area where SFTS is endemic, and there have been no prior reports of JSF. They exhibited clinical symptoms and laboratory test results closely resembling those of SFTS. Therefore, they were initially misdiagnosed with SFTS in their local hospitals. The 3 patients who arrived at our hospital 7 days after symptom onset and were subsequently diagnosed with JSF by metagenomic next-generation sequencing (mNGS). Doxycycline treatment for 1 week. The patients' symptoms quickly improved with no side effects, and the results of laboratory tests went back to normal. By comparing the clinical characteristics of JSF patients and SFTS patients comprehensively, we found that APTT and procalcitonin levels may be valuable in assisting in the identification of SFTS and JSF. In all areas where tick-borne diseases are endemic, include SFTS-epidemic areas, we recommend using the Weil-Felix test to screen for potential rickettsiosis in patients presenting with fever and thrombocytopenia with or without rash in primary healthcare settings, as well as simultaneous testing for the SFTS virus and spotted fever group rickettsioses sequence. Additionally, mNGS sequencing should be used to confirm the diagnosis and provide information for epidemiological investigations in patients who are suspected of having spotted fever group rickettsiosis.

Long-Term Protective Immunity against Ehrlichia chaffeensis Infection Induced by a Genetically Modified Live Vaccine.

Human monocytic ehrlichiosis, an emerging tick-borne disease, is caused by Ehrlichia chaffeensis. Infections with the pathogen are also common in the canine host. Our previous studies demonstrated that functional disruption within the E. chaffeensis phage head-to-tail connector protein gene results in bacterial attenuation, creating a modified live attenuated vaccine (MLAV). The MLAV confers protective immunity against intravenous and tick transmission challenges one month following vaccination. In this study, we evaluated the duration of MLAV protection. Dogs vaccinated with the MLAV were challenged with wild-type E. chaffeensis via intravenous infection at 4-, 8-, and 12-months post-vaccination. Immunized dogs rapidly cleared the wild-type pathogen infection and tested positive for bacteremia less frequently than unvaccinated controls. While immune responses varied among dogs, vaccinees consistently mounted IgG and CD4+ T-cell responses specific to E. chaffeensis throughout the assessment period. Our findings demonstrate that MLAV-mediated immune protection persists for at least one year against wild-type bacterial infection, marking a major advancement in combating this serious tick-borne disease. The data presented here serve as the foundation for further studies, elucidating the molecular mechanisms underlying virulence and vaccine development and aiding in preventing the diseases caused by E. chaffeensis and other tick-borne rickettsial pathogens.