Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis - United States

Presenting Symptoms and Delayed Diagnosis of Ehrlichiosis

Objective

To describe the presenting symptoms, outcomes, and time to diagnosis of ehrlichiosis cases treated at Mayo Clinic, Jacksonville, Florida.

Patients and Methods

We conducted a retrospective analysis of all patients with ehrlichiosis who were treated at Mayo Clinic in Florida from January 1, 2018, to November 1, 2021. Ehrlichiosis was diagnosed via positive serologic or polymerase chain reaction tests. Abstracted variables included patient demographic characteristics, presenting symptoms, outcomes, and time to diagnosis.

Results

Out of 67 patients with ehrlichiosis who were treated at our institution during the study period, 22 were included in our analysis. These patients had diverse presenting symptoms; fever and malaise were common, and severe cases included altered mental status and septic shock. Laboratory test findings included thrombocytopenia, as well as elevated liver enzyme levels and abnormal kidney function. The time to diagnosis varied among the cases studied, with a median time from admission to diagnosis of 4 days.

Conclusion

Prompt treatment with doxycycline was effective, but delayed diagnosis remains a challenge. Our findings underscore the importance of considering ehrlichiosis in differential diagnoses, especially in endemic areas, and emphasize the need for early intervention to prevent severe outcomes.

One health approach to Rickettsia spp.: Brazilian indigenous individuals, their dogs and ticks, and healthcare professionals

Although Indigenous populations have historically overlapped the occurrence of vector-borne pathogens, no One Health approach study has investigated Rickettsia spp. in indigenous communities worldwide. Accordingly, the aim of this study was to investigate anti-Rickettsia spp. antibodies in indigenous individuals, their dogs and healthcare professionals, and Rickettsia spp. infection in ticks from ten indigenous communities of southern and southeastern Brazil. In overall, 66/771 (8.6 %) indigenous individuals, 9/99 (9.1 %) healthcare professionals and 116/386 (30.1 %) dogs were seropositive for at least one out four Rickettsia species tested by immunofluorescence assay (IFA). Out of 603 ticks collected from dogs in indigenous communities, 9/190 (4.7 %) tested positive to fragment of Rickettsia gltA gene by real-time PCR. The homologous antigenic reactions in dogs were significantly more frequent for R. bellii when compared to R. parkeri and R. amblyommatis and may be associated with the high diversity of hard and soft ticks in Americas, and R. bellii capacity of inhibiting another pathogenic rickettsia. Tick bite history increased the seropositivity (odds ratio = 9.29; p = 0.019) in healthcare professionals. This difference may be consequence of higher capacity to recognize tick bites by healthcare professionals, which highlighted the necessity of health care education for indigenous individuals for prevention and early recognition of tick-borne diseases in indigenous communities. In addition, the One Health approach herein has provided a holistic understanding of Rickettsia spp. infection in such communities and correspondent healthcare personal.

Enhanced surveillance for tick-borne rickettsiosis and ehrlichiosis in North Carolina: Protocol and preliminary results

North Carolina (NC) experiences some of the highest incidence rates of spotted fever rickettsiosis (SFR) and ehrlichiosis in the United States (US). Due to the non-specific nature of clinical symptoms, minimal utilization of molecular methods when appropriate, and limitations of sero-diagnostic methods, accurate case identification and subsequent public health reporting is challenging. Herein we detail the protocol and early enrollment results for an enhanced surveillance project aiming to generate more accurate estimates of tick-borne disease incidence in NC. Secondary outcomes of interest include: (i) increasing the obtainment rate of convalescent samples (ii) defining demographic and socioeconomic, behavioral/knowledge, entomologic, and environmental risk factors for disease, and (iii) describing the spectrum and clinical course of disease among cases of SFR and ehrlichiosis up to 90 days after symptom onset. In addition, we will collect remnant serum to establish a biorepository of well characterized samples that we intend to make available to researchers. Of the 150 participants enrolled, highlighted results include 49.5% of participants reported being exposed in their own home compared to 43.2% being exposed due to work or travel showing the importance of tick control and education. We also reported more confirmed cases of SFR and ehrlichiosis (15 and 20 respectively) where the North Carolina State Health Department only reported 14 and 11 confirmed cases in the entire state in 2022. Findings from the project will be reported in subsequent publications.

Epidemiology of Intracellular Bacterial Pathogens Rickettsia Spp., Borrelia Spp., Coxiella Spp., and Bartonella Spp. in West Africa from 2000 to 2023: A Systematic Review

Background: Intracellular bacteria such as Rickettsia spp., Borrelia spp., Coxiella spp., and Bartonella spp. cause febrile illnesses similar to malaria and arboviruses, leading to under-reporting in sub-Saharan Africa. Methods: Following Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines, we included studies on these bacteria in humans, animals, and vectors in West Africa (2000-2023). Case reports, editorials, studies on other pathogens, and coinfections were excluded. Data was retrieved from African Journals Online, Google Scholar, and PubMed (last search: December 31, 2023). The risk of bias was assessed using an adapted Cochrane RoB 2.0 tool. Data were analyzed using Excel 2016 and QGIS. A random-effects model estimated prevalence, with subgroup analysis based on country, detection method, period, and host type. Heterogeneity was measured via the I2 index (>50% indicating moderate heterogeneity). Publication bias was assessed by stratifying studies by risk of bias. Results: Out of 27 articles included, 10 covered studies on Rickettsia spp., 5 Borrelia spp., 6 Coxiella spp., 3 Bartonella spp., and 3 both Rickettsia spp. and Coxiella spp. Among them, 10 studies focused on vectors, 5 on animals, 5 on humans, and 7 on One Health. The prevalence of Rickettsia spp. was the highest in humans, 19.46%, 95% confidence interval: [19.42-19.50]. Bartonella spp. had the highest prevalence in animals, 82.57%, 95% CI: [82.46-82.69], and vectors 37.62%, 95% CI: [37.53-37.71]. Prevalence increased significantly post 2010 (81.4%). PCR-based detection showed a higher prevalence (63%). In the risk-of-bias analysis, the quality of the studies, which were included, did not affect the results and overall validity of findings. Conclusion: Intracellular bacteria spread widely among humans, animals, and vectors. One Health approach is essential for managing zoonotic bacterial diseases in Africa. Variation in prevalence underlines the need for methodological standardization and future research should focus on harmonizing methods by integrating molecular methods.

Temporal trends in diagnostic evolutions for rickettsial diseases including scrub typhus: a bibliometric study

The bibliometric analysis aimed to assess the bibliometric characteristics, current status and temporal trends in diagnostic evolutions related to infectious diseases caused by the genus Orientia and Rickettsia. Relevant studies were retrieved from Scopus using pre-determined standard keywords. The analysis was performed using the R package 'Bibliometrix' through the 'Biblioshiny' interface. A total of 239 studies were identified for Rickettsia diagnostics, while 168 studies focussed on scrub typhus diagnostics. The annual growth rate of publications in scrub typhus (1.82%) was found to be higher than that of diagnostic research in Rickettsia (1.44%). The Journal of Clinical Microbiology (IF: 5.8) was the most relevant source for Rickettsia research, whereas the American Journal of Tropical Medicine and Hygiene (IF: 3.7) led publications for scrub typhus. The most globally cited articles were authored by Biggs et al (2017) for Rickettsia and Blacksell et al. (2007) for scrub typhus. U.S.A. (n = 119) and India (n = 136) are the most productive nations, publishing in Rickettsia and scrub typhus diagnostics. Mahidol University (Thailand) and the University of Texas (U.S.A.) were the top-contributing institutions. Blacksell S.D. and Raoult D. were identified as the most prolific researchers in Rickettsia and scrub typhus diagnostics. This study provides insights into the impact, productivity, and collaborative patterns among authors, institutions, and other stakeholders in rickettsial disease diagnostics. It offers a historical overview of diagnostic developments and emphasizes the importance of continued innovation and international collaboration to ensure timely diagnosis and treatment of rickettsial diseases.

Hospital-Based Surveillance of Rickettsial Diseases in Kashmir, North India

Background: Rickettsial diseases were reported from Kashmir, India, in the early 20th century. Since then, limited research was carried that has resulted in a significant gap in understanding these diseases. This study was conducted to find out the prevalence and diversity of rickettsial diseases in this region. Methods: Blood sample from 476 patients were collected. Enzyme-linked immunosorbent assay was done for the detection of IgM and IgG, and immunofluorescence assay was done for endpoint titer determination. Nested polymerase chain reaction was performed for detection of spotted fever group (gltA, sca0, sca5 genes), typhus group (17 kDa gene) scrub typhus group (47 and 56 kDa gene), followed by sequencing and phylogenetic analysis. Results: The seropositivity of scrub typhus, spotted fever group, typhus group was 74 (15.54%), 71 (14.91%), and 60 (12.60%), respectively. Scrub typhus was significantly associated with the urban population (odds ratio = 1.812, 95% confidence interval 1.099-3.0, p = 0.02). Bimodal seasonal variation was observed in all the three groups. In spotted fever group, out of 48 samples 81.25%, 45.83%, and 38.09% were positive for gltA, sca0, and sca5 genes, respectively, and in typhus group 20.83% were positive for 17 kDa. In the scrub typhus group, out of 62 samples, the 56 kDa gene was positive in 56.45%, while the 47 kDa gene was positive in 35.48%. Phylogenetic analysis revealed Rickettsia conorii, Rickettsia parkeri, Rickettsia typhi, and Orientia tsutsugamushi. Conclusions: This study confirms the presence of human rickettsial infections in Kashmir, highlighting the need for including rickettsial diseases in diagnostic algorithm for acute febrile illness.

Bilateral acute multifocal retinitis and retinal vasculitis secondary to Rickettsia typhi infection

PURPOSE

To describe a case of acute multifocal retinitis (AMR) and retinal vasculitis associated with Rickettsia typhi.

METHODS

Case report.

RESULTS

A 37-year-old previously healthy female presented with acute bilateral panuveitis that was preceded by a febrile illness with pneumonitis and transaminitis. On exam she had bilateral multifocal small white retinal lesions, vascular sheathing, and hemorrhages. The retinal lesions, which appeared consistent with infiltrates and/or ischemia, were confined within the inner or middle retinal layers on optical coherence tomography (OCT) and corresponded to late leakage on fluorescein angiography (FA). There was no evidence of choroidal involvement on indocyanine green angiography (ICGA). Based on the imaging findings and history, the diagnosis of AMR with associated small vessel retinal vasculitis was made and the patient was started empirically on doxycycline. Workup was positive for R. typhi. At follow-up, there was resolution of visual symptoms and nearly all retinal lesions.

CONCLUSIONS

Rickettsial disease should be highly suspected in a patient with AMR and occlusive small vessel vasculitis. Retinal lesions may be either infiltrative or ischemic in nature. Diagnosis, which can be aided by multimodal retinal imaging, is essential for prompt initiation of appropriate antibiotic therapy.

Diversity of Ticks and Rickettsiae in the Southwestern United States: Implications for Public Health

Background: Surveillance is important in addressing the significant public health concerns posed by tick-borne diseases. However, the southwestern U.S. presents particular challenges due to diverse tick fauna and varied ecologies. Methods: From 2021 to 2022, we conducted a partner-based tick surveillance program in Arizona and California to assess the presence of Rickettsia spp. pathogens and species composition of tick vectors. Results: A total of 913 ticks was collected, comprising in descending abundance Rhipicephalus sanguineus, Dermacentor similis, Ixodes pacificus (I. pacificus), Argas sp., Otobius megnini, and Haemaphysalis leporispalustris. Arizona submitted predominantly brown dog ticks (90.05% of all ticks from Arizona), while California showed greater tick species richness with five species identified. No Rickettsia rickettsii was detected, but a variety of other Rickettsia spp. was found in ticks from both Arizona and California and included Rickettsia rhipicephali (R. rhipicephali), Rickettsia massiliae, and Rickettsia monacensis-like rickettsial agents of I. pacificus, and two rickettsial organisms that were not identified to species: one Rickettsia montanensis or Rickettsia raoultii-like, and the other most similar to Candidatus Rickettsia tarasevichiae (R. tarasevichiae). Conclusion: This research contributes to our understanding of tickborne diseases in the southwestern U.S., and emphasizes the need for targeted surveillance and intervention initiatives in a region with complex relationships among ticks, hosts, and Rickettsia species. In particular, the finding of an apparently novel pairing of an unknown Argas sp. tick and R. tarasevichiae-like organism suggests that argasid species are an important target for future research. In addition, the results-both tick species submitted and resulting Rickettsia spp. identified-highlights the strengths and potential biases associated with a partner-based sampling method for tick surveillance.

Increased Recognition of Human Anaplasmosis, Ontario, Canada, 2021

Human granulocytic anaplasmosis is a tickborne infection characterized by fever, thrombocytopenia, leukopenia, transaminitis, or a combination of those. Treatment must be prompt and appropriately targeted to prevent clinical decompensation. We discuss an unusual cluster of 16 probable cases in Ontario, Canada, during June-August 2021.

Antibodies to Anaplasma phagocytophilum in Patients with Human Granulocytic Anaplasmosis Confirmed by Both Polymerase Chain Reaction and Culture

BACKGROUND/AIMS

Sera from patients from a single medical institution in New York State with human granulocytic anaplasmosis established by a positive polymerase chain reaction test (PCR) for Anaplasma phagocytophilum were used to assess the performance of serologic testing. All cases were also confirmed by culture in order to eliminate any false positive PCR samples.

METHODS

A nested PCR was performed targeting the heat shock operon of A. phagocytophilum. Culture was done using the HL-60 promyelocytic cell line. Serologic testing was performed to detect IgG/A/M using an indirect immunofluorescence assay that incorporated a human isolate of A. phagocytophilum as the source of the antigen.

RESULTS

From 1997 to 2009, 38 human granulocytic anaplasmosis patients were evaluated. On the baseline serum sample 21 (55.3%; 95% CI: 38.3%-71.4%) had a positive serologic test; 7 samples (33.1%) were positive at a titer of 80-320 and 14 samples (66.7%) at a titer of at least 640. Sixteen (94.1%) of the 17 with a negative baseline test had follow-up testing performed. All 16 tested positive on a convalescent phase serum sample obtained from 6 to 45 days later.

CONCLUSION

PCR testing is the most commonly used direct diagnostic test to diagnose human granulocytic anaplasmosis. Our findings demonstrate that only approximately 55% of the PCR and culture positive cases were also seropositive on blood samples obtained at the same time point, indicating that serologic testing performed at the time of presentation has limited sensitivity. However, all of the 16 evaluable seronegative patients developed antibodies to A. phagocytophilum during convalescence.

Serologic and molecular survey for Rickettsia in small mammals in the Andes of Colombia

Zoonotic vector-borne infectious diseases represent a significant global challenge. Ticks are one of the most important vectors globally, transmitting a wide range of pathogens. Among these pathogens, bacteria of the genus Rickettsia cause zoonotic diseases, knows as rickettsioses, that primarily affect tropical and subtropical regions. Rickettsiae are transmitted between vertebrate hosts and vectors, with some wild mammals serving as key amplifying hosts. In Colombia, the limited information on wild reservoirs contrasts with their high diversity, which includes 553 native mammal species, and 51 species of ticks associated with wild mammal hosts. To detect Rickettsia exposure and infections in wild mammals from the Colombian Andean region, serum, blood, and organ samples were collected from wild mammals in the Departments of Caldas and Risaralda, Colombia, between July 2021 and November 2022. A total of 147 mammals belonging to 58 species and three orders (Didelphimorphia, Chiroptera, and Rodentia) were captured. The indirect immunofluorescence assays analysis detected antibodies for Rickettsia in 100 % of didelphids, 65.2 % of rodents, and 45.9 % of bats. Rickettsia DNA was detected in 4.1 % of the mammals analyzed, with 'Candidatus Rickettsia andeanae', Rickettsia felis, Rickettsia rickettsii, and Rickettsia parkeri identified in rodents and bats. The detection of Rickettsia in wild mammals reinforces their role as reservoirs and highlights the need to investigate their ecology to improve surveillance and control of rickettsiosis in Colombia.

The epidemiology and clinical manifestations of anaplasmosis in humans: A systematic review of case reports

Anaplasmosis, caused by Anaplasma phagocytophilum, is an emerging tick-borne disease affecting humans and animals with a broad spectrum of clinical manifestations. This systematic review and analysis aimed to synthesise the epidemiology, clinical features, diagnostic methods, and treatment outcomes of anaplasmosis, emphasising enhanced surveillance and management strategies. The systematic review encompassed 73 cases from various geographic regions, revealing fever as the predominant symptom, alongside myalgia, headache, chills, and arthralgia. Molecular testing, particularly PCR, emerged as the primary diagnostic tool, aiding in identifying Anaplasma species. Co-infections are uncommonly described in the cases analysed, showing borreliosis and viral infections, underscoring the complexity of disease presentation. Doxycycline monotherapy demonstrated high efficacy, with a low mortality rate, while alternative antimicrobial options and combination therapy were considered in specific scenarios. This study contributes to understanding anaplasmosis's global burden and highlights the importance of continued research and collaborative efforts to mitigate its impact on public health.

In silico construction of a multi-epitope vaccine (RGME-VAC/ATS-1) against the Rickettsia genus using immunoinformatics

BACKGROUND

Rickettsia is a genus of Gram-negative bacteria that causes various diseases, including epidemic typhus, Rocky Mountain spotted fever, and Mediterranean spotted fever. Ticks transmit these diseases and commonly found in developing regions with poor sanitation. As a result, it is difficult to estimate the number of these diseases cases, making it challenging to create prevention and diagnostic mechanisms.

OBJECTIVES

Thus, this study aimed to develop an in silico multi-epitope vaccine against Rickettsia.

METHODS

Eight proteins were previously identified as potential vaccine candidates through reverse vaccinology and were screened for epitopes that bind to MHC class I and II molecules. The epitopes were then analysed for antigenicity, allergenicity, and toxicity. The selected epitopes were linked with AAY and GPGPG sequences peptide and a known adjuvant, the B-chain of Escherichia coli heat-labile enterotoxin, to form a chimeric multi-epitope protein. The protein's three-dimensional structure was predicted, and molecular docking analysis was performed against the toll-like receptor 4 (TLR4). Finally, the immune response to the protein was simulated using C-ImmSim tool.

FINDINGS

A total of 26 immunogenic epitopes, formed the multi-epitope vaccine RGME-VAC/ATS-1. The vaccine showed excellent immunogenic parameters and was predicted to do not be toxic or allergenic to the host. It also showed good potential stimulation of immune cells, with a propensity to generate memory cells and elicit IFN-γ secretion.

MAIN CONCLUSIONS

The in silico validations suggest that our study successfully designed an innovative multi-epitope vaccine against Rickettsia, addressing the challenges posed by the elusive nature of diseases caused by this genus. We provide a promising potential for further experimental exploration and the development of targeted prevention and diagnostic strategies for these diseases.

A new spotted fever group Rickettsia genotype in Haemaphysalis leporispalustris from Maine, USA

Spotted fever group (SFG) rickettsioses are increasingly recognized worldwide as threats to public health. Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia rickettsii subspecies californica cause spotted fever rickettsioses, including Rocky Mountain spotted fever. These disease agents are transmitted to humans by various tick vectors in the United States. There is growing concern that other tick species, such as Haemaphysalis leporispalustris, may also transmit new and potentially unrecognized SFG rickettsial pathogens. In this study, we found that 6.1 % of 296 questing H. leporispalustris ticks (21 larvae, 260 nymphs, 9 males, and 6 females) collected from 38 towns across nine counties in Maine, USA, were positive for Rickettsia spp. Further multilocus sequence typing and phylogenetic analysis revealed that this is a new Rickettsia genotype (Rickettsia sp. ME2023) belonging to the SFG group and close to Candidatus Rickettsia lanei. Tick vectors and rickettsial species associated with SFG rickettsioses in New England warrant further investigation. Additionally, the role of H. leporispalustris in pathogen enzootic cycles and transmission requires further study.

Donor-Derived Ehrlichiosis Caused by Ehrlichia chaffeensis from Living Donor Kidney Transplant

Tickborne infections are challenging to diagnose, particularly among solid organ transplant recipients. We report a US case of donor-derived ehrlichiosis from a living kidney donation that highlights how screening for living donors may miss tickborne infections. Clinicians should consider the epidemiology of the donor when screening donations and evaluating recipients for donor-derived infection.

Derivation and Internal Validation of a Clinical Prediction Model for Diagnosis of Spotted Fever Group Rickettsioses in Northern Tanzania

Spotted fever group rickettsioses (SFGR) pose a global threat as emerging zoonotic infectious diseases; however, timely and cost-effective diagnostic tools are currently limited. We used data from 449 patients presenting to 2 hospitals in northern Tanzania between 2007 and 2008, of which 71 (15.8%) met criteria for acute SFGR based on ≥4-fold rise in antibody titers between acute and convalescent serum samples. We fit random forest classifiers incorporating clinical and demographic data from hospitalized febrile participants as well as Earth observation hydrometeorological predictors from the Kilimanjaro Region. In cross-validation, a prediction model with 10 clinical predictors achieved an area under the receiver operating characteristic curve of 0.65 (95% confidence interval, .48-.82). A combined prediction model with clinical, hydrometeorological, and environmental predictors (20 predictors total) did not significantly improve model performance. Novel strategies are needed to improve the diagnosis of acute SFGR, including the identification of diagnostic biomarkers that could enhance clinical prediction models.

A Case of Japanese Spotted Fever Coinciding With COVID-19 That Progressed to Septic Shock and Cardiac Arrest: A Case Report

Japanese spotted fever is a tick-borne infectious disease caused by Rickettsia japonica. Early treatment is crucial to prevent deterioration and death. We present a case of an 82-year-old male with Japanese spotted fever coinciding with coronavirus disease 2019 (COVID-19). Initially diagnosed with COVID-19 via a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen test at a clinic and advised to recuperate at home, the patient already exhibited a rash at the time of diagnosis. He later developed difficulty with oral intake and became lethargic. Upon visiting the emergency room, he presented with erythema with purple tints on the trunk and extremities, including palms and soles. Laboratory tests revealed acute kidney injury and hyperkalemia. Suspecting prerenal acute kidney injury due to inadequate oral intake during COVID-19 treatment, we initiated rehydration therapy. The rash was initially attributed to COVID-19, but dermatological examination suggested Japanese spotted fever based on its distribution on the palms and soles, which is atypical for COVID-19. Tick bites were observed on the right thigh, prompting initiation of minocycline. A subsequent polymerase chain reaction (PCR) test later confirmed Japanese spotted fever. The patient deteriorated, experiencing cardiac arrest. He required intensive care but recovered and was transferred to a convalescent rehabilitation hospital. This case highlights the potential for overlooking Japanese spotted fever due to an initial diagnosis of COVID-19. Recognition of distinct rash characteristics led to the correct diagnosis. A thorough physical examination remains crucial, even when a COVID-19 diagnosis has already been made. This article was previously presented as a meeting abstract at the 51st Annual Meeting of the Japanese Society of Intensive Care Medicine on March 14, 2024.

Culture and other direct detection methods to diagnose human granulocytic anaplasmosis

OBJECTIVES

We sought to assess the performance of 3 laboratory tests on blood specimens for direct detection of Anaplasma phagocytophilum, the cause of human granulocytic anaplasmosis (HGA), in patients tested at a single medical institution in New York State.

METHODS

Direct tests included microscopic blood smear examination for intragranulocytic inclusions, polymerase chain reaction (PCR), and culture using the HL-60 cell line. The HGA cases testing positive by only 1 direct test were not included, unless HGA was confirmed by acute or convalescent serology using an indirect immunofluorescent assay.

RESULTS

From 1997 to 2009, 71 patients with HGA were diagnosed by at least 1 of the 3 direct test methods. For the subgroup of 55 patients who were tested using all 3 methods, culture was positive for 90.9% (50/55) vs 81.8% (45/55) for PCR vs 63.6% (35/55) for blood smear (P =.002). Most cultures (79.3%) were detected as positive within 1 week of incubation.

CONCLUSIONS

Although using culture to detect A phagocytophilum is likely not amenable for implementation in most hospital laboratories, in our experience, culture had the highest yield among the direct tests evaluated.

Contribution of Limited Molecular Testing to Low Ehrlichiosis Diagnosis in High Incidence Area, North Carolina, USA

Indirect immunofluorescence antibody assays have been the primary method for laboratory diagnosis of ehrlichiosis. Detection of Ehrlichia spp. DNA by using PCR is now widely available through commercial laboratories. To prepare for Ehrlichia spp. PCR introduction, we assessed ehrlichiosis testing practices, quantified the proportion of samples eligible for PCR testing, and estimated the potential effect of implementing PCR at the University of North Carolina health system in North Carolina, USA, which is in an area with a high-incidence of ehrlichiosis. We found <1% of patient samples underwent PCR testing, even though rates of serodiagnostic algorithm completion (testing of acute and convalescent samples) were low (18.4%). Our findings show a need to educate providers on diagnostic and treatment guidelines for ehrlichiosis and raise awareness of the availability and advantage of PCR testing.

Development of a rapid antigen-based lateral flow assay for tick-borne spotted fever rickettsioses

Tick-borne spotted fever rickettsioses (SFRs) continue to cause severe illness and death in otherwise-healthy individuals due to lack of a timely and reliable diagnostic laboratory test. We recently identified a diagnostic biomarker for SFRs, the putative N-acetylmuramoyl-l-alanine amidase RC0497. Here, we developed a prototype laboratory test that targets RC0497 for diagnosis of SFRs. The concentrations of RC0497 in sera of Rickettsia rickettsii-infected guinea pigs and R. conorii-infected mice were determined by stable isotope dilution-parallel reaction monitoring mass spectrometry (SID-PRM-MS), ranging from 0.1 to 1.1 ng/ml. Using europium chelate nanoparticle reporters, we developed a lateral flow assay (LFA) and evaluated the test with a panel of serum samples of mock and experimentally infected animals. Interestingly, 21 of 22 (95.5%) serum samples from R. rickettsii-infected guinea pigs and R. conorii-infected mice yielded positive results with a ratio of test line / control line greater than the cutoff value determined for non-infected animals. All uninfected samples were in agreement with the intended results, suggesting that the initially assessed specificity of the test is 100%, among these samples. Mice infected with a lethal dose of R. conorii and treated with doxycycline on day 3 post-infection (p.i.), upon RC0497 detection by LFA, displayed significantly decreased rickettsial loads, comparable to the sublethal infection group on day 5 p.i.. A panel of human serum samples spiked with various concentrations of recombinant RC0497 were analyzed by LFA, suggesting that the limit of detection of the LFA was 0.64 ng/mL. These findings suggest that the timely detection of RC0497 by a europium LFA offers guidance for treatment, leading to a significant improvement in infection outcomes. This work, for the first time, shows significant promise for a rapid and easy-to-use platform offering a timely diagnostic assay for severe SFRs.

A Comparison of the Clinical and Epidemiological Profile of Rocky Mountain Spotted Fever with Dengue and COVID-19 in Hospitalized Children, Sonora, México, 2015-2022

BACKGROUND

Rocky Mountain spotted fever (RMSF) is a challenge for physicians because the disease can mimic other endemic febrile illnesses, such as dengue and COVID-19. The comparison of their main clinical and epidemiological manifestations in hospitalized children can help identify characteristics that improve empirical suspicion and timely therapeutic interventions.

METHODS

A cross-sectional study was conducted on a series of patients aged 0 to 18 years, hospitalized between 2015 and 2022, with a diagnosis of RMSF, dengue, or COVID-19. Data were retrieved from medical records. Subjects were categorized as patients with RMSF (group I) and patients with dengue and COVID-19 (group II). Descriptive statistics were used, and differences were evaluated using Student's t-test and the chi-squared test.

RESULTS

A series of 305 subjects were studied, with 252 (82.6%) in group I. Subjects in both groups presented fever, myalgias, arthralgias, and rash, but exposure to ticks distinguished group I. The fatality rate (21.0%) in group I was higher than in group II (3.8%).

CONCLUSIONS

Although fever, myalgias, arthralgias, and rash are common in all three illnesses, they are more prevalent in hospitalized patients with RMSF. In the presence of such symptoms, a history of tick exposure can guide clinical decisions in regions where all three diseases are endemic.

Surveillance of tick-borne pathogens present in ticks (Acari: Ixodidae) removed from companion animals in Louisiana, USA

Current knowledge of tick distribution and tick-borne pathogen presence across Louisiana is limited. Collaborating with veterinarians across the state, ticks removed from companion animals were recovered and assessed for the presence of zoonotic pathogens. A large number of ticks (n = 959) were removed from companion animals and subsequently screened using qPCR for Anaplasma phagocytophilum, Babesia microti, Borrelia burgdorferi, Bartonella henselae, Ehrlichia chaffeensis, and spotted fever group Rickettsia. Five different tick species, Ixodes scapularis (54.5%), Amblyomma americanum (18.4%), Amblyomma maculatum (12.5%), Dermacentor variabilis (11.2%), and Rhipicephalus sanguineus (0.3%) from different regions of Louisiana were collected from October 2018 to July 2019. There were 15 PCR-positive ticks for Rickettsia parkeri (1.6% prevalence), and four ticks were positive for Ehrlichia chaffeensis (0.4% prevalence). This survey identifies ticks and tick-borne pathogens associated with companion animals and areas for future active surveillance.

Core-genome guided novel therapeutic targets identification and chimeric vaccine designing against Rickettsia rickettsii

Rocky Mountain Spotted Fever, caused by the gram-negative intracellular bacteria Rickettsia rickettsii, is a serious tick-borne infection with a fatality rate of 20-30%, if not treated. Since it is the most serious rickettsial disease in North America, modified prevention and treatment strategies are of critical importance. In order to find new therapeutic targets and create multiepitope vaccines, this study integrated subtractive proteomics with reverse vaccinology. The core genome of R. rickettsii was investigated, resulting in the identification of seven essential, human non-homologous proteins as potential drug targets, as well as four antigenic, non-allergenic proteins suitable for vaccine development. Using conserved antigenic peptides, two chimeric vaccine constructs were developed and assessed using molecular docking, molecular dynamics simulations, principal component analysis, MM-GBSA binding free energy, and dynamic cross-correlation matrix studies. The high immunogenic potential was indicated by the vaccine designs' robust and consistent interactions with human immunological receptors. Their capacity to trigger strong humoral and cellular immunological responses was further demonstrated by in silico immune simulations. The persistent interactions of vaccine V1 and V2 with human immunological receptor demonstrated that these might have high immunogenic potential. Moreover, the identified drug targets were annotated for essential biological processes, which shed light on their therapeutic potential. The vaccine constructs were cloned and expressed in suitable systems. This study displays a comprehensive strategy for managing Rocky Mountain Spotted Fever via rational vaccine development. Further experimental research is needed to confirm the immunogenicity of the vaccines and the druggability of identified targets, establishing the path toward effective RMSF management.

Infection prevention in the immunocompromised traveler due to conditions other than transplantation: a review

This narrative review explores the risks related to infection in immunocompromised travelers due to conditions other than transplantation, and evaluates the evidence behind current prophylactic strategies, including immunizations, antimicrobials, and non-pharmacological interventions, to prevent various infection and how the current evidence applies to this special patient population, from the perspective of a US-based traveler.

2024 American Heart Association and American Red Cross Guidelines for First Aid

Codeveloped by the American Heart Association and the American Red Cross, these guidelines represent the first comprehensive update of first aid treatment recommendations since 2010. Incorporating the results of structured evidence reviews from the International Liaison Committee on Resuscitation, these guidelines cover first aid treatment for critical and common medical, traumatic, environmental, and toxicological conditions. This update emphasizes the continuous evolution of evidence evaluation and the necessity of adapting educational strategies to local needs and diverse community demographics. Existing guidelines remain relevant unless specifically updated in this publication. Key topics that are new, are substantially revised, or have significant new literature include opioid overdose, bleeding control, open chest wounds, spinal motion restriction, hypothermia, frostbite, presyncope, anaphylaxis, snakebite, oxygen administration, and the use of pulse oximetry in first aid, with the inclusion of pediatric-specific guidance as warranted.

Risk Factors for Spotted Fever Group Rickettsioses in Kilimanjaro Region, Tanzania

Background

Knowledge gaps exist on risk factors for spotted fever group rickettsioses (SFGR) in sub-Saharan Africa. We sought to identify SFGR risk factors in Kilimanjaro Region, Tanzania.

Methods

We recruited febrile patients presenting at 2 hospitals in Moshi from February 2012 through May 2014. Standardized clinical and risk factor questionnaires were administered. SFGR exposure was defined as a Rickettsia africae immunofluorescence antibody reciprocal titer ≥64, and acute SFGR as a ≥4-fold rise between paired sera. Logistic regression was used to identify associations.

Results

Of 1190 participants providing ≥1 serum sample, the median age was 21.8 (range, 0.3-100.2) years, 646 (54.3%) were female, and 650 (54.6%) had SFGR exposure. Of 731 participants with paired sera, 67 (9.2%) had acute SFGR. On multivariable analysis, odds of acute SFGR were higher in the age group 0-2 years (adjusted odds ratios [aORs] for older age groups, <0.36; P < .011), rural residence (aOR, 4.1; P = .007), and areas with maximum daily temperature <26°C (aORs for higher temperature groups, <0.42; P < .035). Odds of SFGR exposure were higher in those working in the garden (aOR, 1.8; P = .010) and seeing a dog (aOR, 1.5; P = .010). Odds of SFGR exposure were lower in the age group 0-2 years (aORs for older age groups, >1.5; P < .026), female sex (aOR, 0.62; P < .001), and being from the Chaga tribe (aOR, 0.68; P = .003).

Conclusions

Those aged <2 years, rural residents, and persons residing in areas with cooler temperatures had increased odds of SFGR. Our results identify groups for further research on tick exposure and for targeted prevention interventions.

Molecular Detection of Tick-Borne Bacterial Pathogens in Patients With Undifferentiated Febrile Illness in India Using a Flow Chip Assay

BACKGROUND

Tick-borne diseases (TBDs) play a crucial role in human morbidity and mortality, as ticks are highly effective in spreading diseases by transmitting harmful pathogens to humans and animals. The last few decades have seen an increase in the number of recognized tick-borne pathogens and the incidence of TBD worldwide. Several of these diseases are ubiquitous in India. However, in India, there is limited information on the molecular detection of tick-borne pathogens in patients with undifferentiated febrile illness. The study aims to investigate tick-borne pathogens among undifferentiated febrile patients in India using a multiplex polymerase chain reaction (PCR)-based assay.

METHODS

A total of 120 blood samples were collected from patients with undifferentiated febrile illnesses of all ages. The samples were tested for a panel of (seven) tick-borne pathogens (Anaplasma, Ehrlichia, Borrelia, Bartonella, Coxiella, Rickettsia, and Francisella) using a multiplex PCR tick-borne bacterial flow chip (TBFC) assay through a semi-automated HybriSpot platform (Vitro Master Diagnóstica, Granada, Spain).

RESULTS

Among the 120 samples tested, one was positive for spotted fever Rickettsia, two were positive for typhus group Rickettsia, one was positive for Borrelia, and two showed coinfections with Borrelia and Anaplasma.

CONCLUSION

Our knowledge of TBD is steadily advancing with the discovery of novel pathogens and the development of cutting-edge diagnostic tools. Although traditional diagnostic methods like serology and microscopy will remain essential for the diagnosis of TBD, the implementation of advanced molecular diagnostics such as TBFC will enhance our understanding of these diseases by enabling the identification of emerging pathogens and offering more precise and timely diagnoses.

Tick-, flea- and mite-borne pathogens and associated diseases of public health importance in Bangladesh: a review

Background

This scoping review provides a baseline summary of the current records of the ticks, fleas, and mites of public health importance that are present in Bangladesh. It summarizes their geographic distributions and reports the levels of their infestation of livestock, pets, wildlife, and humans, and the clinical and epidemiological studies pertinent to these vectors and their pathogens.

Methods

Sixty-one articles were identified in a literature search, including 43 published since 2011.

Results

Twelve articles contained reliable information on ticks and their associated hosts. However, information on fleas and mites in Bangladesh is very limited. Seventeen species of ixodid ticks that commonly parasitize peridomestic animals and can bite humans are described: Rhipicephalus microplus, R. appendiculatus, R. sanguineus, Haemaphysalis bispinosa, Hyalomma anatolicum, and Amblyomma testudinarium. Thirty-eight veterinary articles describe livestock pathogens, including Babesia, Anaplasma, and Theileria, and the diseases they cause. Few of those studies used modern molecular techniques to identify these pathogens. Eleven articles reported human diseases or surveillance studies, 10 from the last 10 years. Two country-wide serosurveys of 1,209 and 720 patients, using Enzyme Linked Immunosorbent Assay (ELISA) and Indirect Immunofluorescence Assay (IFA), respectively, reported human exposure to Orientia tsutsugamushi (8.8%-23.7%), typhus and spotted-fever group rickettsiae (19.7%-66.6%), and Coxiella burnetii (3%). The seropositivity rates varied regionally. PCR-based studies confirmed that febrile patients in Bangladesh may be infected with O. tsutsugamushi, Rickettsia typhi, Rickettsia felis, or Bartonella elizabethae. Only limited molecular research has been done with dogs and cats. These studies have reported PCR-confirmed canine infections with Babesia gibsoni (30%), Anaplasma bovis (58%), or Rickettsia monacenis (14%, n=50), and feline infections with Rickettsia felis (21%, n=100). Similarly, fleas from cats tested positive for Rickettsia felis (20.6%).

Conclusions

These findings indicate that diseases borne by non-mosquito vectors in Bangladesh urgently require more attention from public health, medical, and veterinary specialists to establish their true occurrence.

Typhus group Rickettsia community-acquired bacterial central nervous system infections: We must think outside the box!

Typhus group rickettsiosis (TGR), caused by Rickettsia typhi and Rickettsia prowazekii, are globally distributed vector-borne diseases with increasing cases. Diagnosis is usually clinical, confirmed by seroconversion of IgG antibodies. Human infection occurs in diverse geographic areas with some developing CNS infection characterized by fever, headache, meningismus, and/or focal signs - usually beyond the first week of initial symptomatology. Seizures and other CNS manifestations have been observed. When untreated, infection may result in neurologic sequelae and even death. This study presents a systematic review of all documented cases of Rickettsia typhi meningoencephalitis published since 2015 with the addition of five cases of TGR in South Coastal Texas, USA. This review followed the guidelines outlined in PRISMA. A schematic explanation of the pathophysiology is offered. CSF may present with high opening pressure, mild to moderate pleocytosis, mildly elevated protein levels, and low csf/serum glucose ratio, or normal findings. Meningeal enhancement, intracranial hypertension, and focal abnormalities have been described in imaging studies, but can be normal. Treatment with doxycycline leads to prompt resolution of symptoms. Failure to initiate early empiric treatment can lead to serious consequences. The study recommends routine testing for TGR in patients from endemic areas with classical symptoms when other diagnoses are inconclusive or in cases with atypical presentations. The authors advocate for incorporating empiric treatment for murine typhus into community-acquired bacterial meningitis guidelines in endemic areas; and stress the importance of enhancing laboratory diagnostic capabilities in public health entities world-wide. Further studies of community acquired mengingoencephalitis caused by TGR are highly encouraged.

Rocky Mountain Spotted Fever in Children along the US‒Mexico Border, 2017-2023

Rocky mountain spotted fever (RMSF) causes significant illness and death in children. Although historically rare in California, USA, RMSF is endemic in areas of northern Mexico that border California. We describe 7 children with RMSF who were hospitalized at a tertiary pediatric referral center in California during 2017-2023. Five children had recent travel to Mexico with presumptive exposure, but 2 children did not report any travel outside of California. In all 7 patients, Rickettsia rickettsii DNA was detected by plasma microbial cell-free next-generation sequencing, which may be a useful diagnostic modality for RMSF, especially early in the course of illness, when standard diagnostic tests for RMSF are of limited sensitivity. A high index of suspicion and awareness of local epidemiologic trends remain most critical to recognizing the clinical syndrome of RMSF and initiating appropriate antimicrobial therapy in a timely fashion.

Frequency of tick bites and associated care-seeking behaviors in the United States

Tick-borne diseases are commonly reported in the United States, but frequency of tick bites and care-seeking behaviors following tick bites are poorly understood. We used nationally representative survey data to describe the frequency of tick bites among people living in the United States and how often, where, and why care-seeking associated with tick bites occurs. We found that over 31 million people (nearly 1 in 10) living in the United States might experience a tick bite each year and highlight regional trends in associated care-seeking behaviors. These findings emphasize the need for effective tick bite prevention education and regionally tailored healthcare provider recommendations for management of tick-borne diseases.

Meningitis and neurosensory hypoacousia due to Rickettsia sp. in Peru: case report

BACKGROUND

We present the case of a young female health worker, resident in a high Andean region of Peru, with recent exposure to farm animals and arthropods, who developed acute febrile undifferentiated syndrome, severe thrombocytopenia and pulmonary and abdominal extravasation. Subsequently, the patient developed meningitis and early onset bilateral neurosensorial hypoacusis and showed reactive serology to acute infection by Rickettsia sp. Epidemiological and clinical considerations in the differential diagnosis for early management are discussed.

Vector-Borne Zoonotic Lymphadenitis-The Causative Agents, Epidemiology, Diagnostic Approach, and Therapeutic Possibilities-An Overview

In addition to common skin pathogens, acute focal lymphadenitis in humans can, in rare cases, be caused by a zoonotic pathogen. Furthermore, it can develop in the absence of any direct or indirect contact with infected animals, in cases when the microorganism is transmitted by a vector. These clinical entities are rare, and therefore often not easily recognized, yet many zoonotic illnesses are currently considered emerging or re-emerging in many regions. Focal zoonotic vector-borne lymphadenitis and its numerous causative agents, with their variegated clinical manifestations, have been described in some case reports and small case series. Therefore, we summarized those data in this narrative overview, with the aim of raising clinical awareness, which could improve clinical outcomes. This overview briefly covers reported pathogens, their vectors and geographic distribution, and their main clinical manifestations, diagnostic possibilities, and recommended therapy. Vector-borne tularemia, plague, bartonellosis, rickettsioses, borreliosis, and Malayan filariasis are mentioned. According to the existing data, when acute focal bacterial vector-borne zoonotic lymphadenitis is suspected, in severe or complicated cases it seems prudent to apply combined aminoglycoside (or quinolone) plus doxycycline as an empirical therapy, pending definite diagnostic results. In this field, the "one health approach" and further epidemiological and clinical studies are needed.

Safety profiles of tetracycline-class drugs: a pharmacovigilance analysis of the FAERS database

BACKGROUND

As synthesis technology advances, novel and efficient derivatives of tetracyclines are found. Three new antibiotics were approved within the past 18 years, and represent a new era in the use of tetracyclines. To gain further insight into adverse events linked to tetracyclines and better protect pediatric patients, ongoing monitoring of safety data is crucial.

METHODS

The FAERS data from the first quarter of 2004 to the third quarter of 2023 in the AERSMine were extracted to conduct disproportionality analysis. The association between five tetracyclines and adverse events was evaluated using reporting odds ratio, and their risk factors were explored by multivariate logistic regression analysis.

RESULTS

Our study showed that thyroid gland disorders had the strongest signal in children. Patients aged 12-18 and treatment with minocycline are risk factors for thyroid adverse events (12-18: OR = 10.727 [7.113-16.177], p < 0.0001; minocycline: OR = 17.025 [10.475-27.678], p < 0.0001). Second-generation tetracycline and third-generation tetracycline ADR patterns differed. Blood fibrinogen decreased and hypofibrinogenaemia was primarily reported with tigecycline and eravacycline.

CONCLUSION

This study provided basic evidence for further research on tetracyclines-related adverse events. However, the safety of third-generation tetracycline in children requires additional validation through a large-scale prospective study.

A compartment and metapopulation model of Rocky Mountain spotted fever in southwestern United States and northern Mexico

Rocky Mountain spotted fever (RMSF) is a fatal tick-borne zoonotic disease that has emerged as an epidemic in western North America since the turn of the 21st century. Along the US south-western border and across northern Mexico, the brown dog tick, Rhipicephalus sanguineus, is responsible for spreading the disease between dogs and humans. The widespread nature of the disease and the ongoing epidemics contrast with historically sporadic patterns of the disease. Because dogs are amplifying hosts for the Rickettsia rickettsii bacteria, transmission dynamics between dogs and ticks are critical for understanding the epidemic. In this paper, we developed a compartment metapopulation model and used it to explore the dynamics and drivers of RMSF in dogs and brown dog ticks in a theoretical region in western North America. We discovered that there is an extended lag-as much as two years-between introduction of the pathogen to a naïve population and epidemic-level transmission, suggesting that infected ticks could disseminate extensively before disease is detected. A single large city-size population of dogs was sufficient to maintain the disease over a decade and serve as a source for disease in surrounding smaller towns. This model is a novel tool that can be used to identify high risk areas and key intervention points for epidemic RMSF spread by brown dog ticks.

Diagnosis of a Rare Rickettsia felis Infection Complicated with Unusual Pericardial Effusion and Cardiac Tamponade Using an mNGS Test

The occurrence of sporadic rickettsial infections has been consistently undervalued and overlooked, primarily owing to a limited emphasis on routine examinations for rickettsioses in clinical practice. At present, the immunofluorescence assay is the prevailing diagnostic method for suspected rickettsioses that enables the detection of specific antibodies against rickettsia in human serum. Herein, we present an exceptional instance of rickettsial infection that was characterized by a rare manifestation of extensive pericardial effusion leading to dyspnea and cardiac tamponade. A diagnosis of chronic fibrosing pericarditis was established based on pericardium tissue obtained through pericardiotomy, and a conclusive metagenomic next-generation sequencing test confirmed the presence of Rickettsia felis infection. The cat flea, scientifically known as Ctenocephalides felis, is the predominant carrier of R. felis. An escalating incidence of human R. felis infections has raised concerns, particularly in light of the burgeoning population of domesticated animals in many contemporary societies.

Prevalence, Clinico-Laboratory Features and Outcomes of Paediatric Scrub Typhus Cases in a Tertiary Care Centre in Eastern India: A prospective observational study

Objectives

Scrub typhus is the most common rickettsial disease in India, caused by Orientia tsutsugamushi and transmitted by chigger mites. Previously prevalent in South India, a resurgence of scrub typhus cases has recently affected Eastern India. This study aimed to estimate the prevalence and describe the clinico-laboratory profile of scrub typhus in paediatric patients (1-12 years old) living in Eastern India.

Methods

This prospective observational study was conducted from January to December 2019 at the Dr B C Roy Post Graduate Institute of Paediatric Sciences, Kolkata, India. All acute undifferentiated cases of febrile illness, in patients aged between 1-12 years, were tested using scrub typhus serology by ELISA. Demographic details, clinical features, laboratory findings, complications and treatment outcomes of these scrub typhus patients were extracted and analysed.

Results

Out of 1,473 patients with acute febrile illness, 67 (4.5%) children were diagnosed with scrub typhus. The mean age of the selected patients was 5.22 ± 3.05 years, and the majority (64.2%) had been running a fever since the preceding 7-14 days. Gastrointestinal symptoms such as vomiting (43.3%) and abdominal pain (32.8%) were most frequently observed. Major clinical signs of scrub typhus were hepatomegaly (41.8%) and splenomegaly (31.3%). Complications were observed in 74.6% of patients, with thrombocytopenia (40.3%) and meningoencephalitis (29.9%) occurring more frequently. The case fatality rate of the study sample was 1.5%.

Conclusion

Classical eschar was absent in three-fourth of the studied patients. Hence, this study advocates laboratory scrub typhus tests for all suspected cases in the endemic region (Eastern India). Prompt treatment with doxycycline and/or azithromycin could prevent complications such as thrombocytopenia/meningoencephalitis and reduce mortality.

Novel Rickettsia and host records for argasid ticks, including Alveonasus cooleyi, on wild mammals in Baja California, Mexico

We conducted surveillance of mammals to investigate their associations with argasid ticks and tick-borne pathogens. During 2021, a total of 20 wild carnivores and 57 lagomorphs were sampled, and 39 argasid ticks belonging to two species were collected. All mammals and ticks were tested by molecular assays to detect Borrelia and Rickettsia infections. Nine ticks identified as Otobius megnini were collected from two coyotes (Canis latrans) and 30 Alveonasus cooleyi (McIvor 1941) were collected from six bobcats (Lynx rufus) and one rabbit (Sylvilagus auduboni). We detected Rickettsia spp. DNA in 21 of the 27 (77.8%) tested Av. cooleyi and none of the O. megnini. No ticks were PCR-positive for borreliae and all mammals were PCR-negative for both pathogen genera. Phylogenetic analysis based on gltA, htrA, and 16 S rRNA targets revealed that all rickettsiae from Av. cooleyi clustered with ancestral group rickettsiae, likely representing a novel species of possibly endosymbiotic Rickettsia. The significance of Av. cooleyi and the newly identified Rickettsia sp. to the health of wildlife is unknown, and further work is indicated to determine whether they may be relevant to public health or carnivore conservation.

Human granulocytotropic anaplasmosis-A systematic review and analysis of the literature

Human granulocytotropic anaplasmosis (HGA) is a zoonotic tick-borne bacterial infection caused by Anaplasma phagocytophilum. While most cases are reported from North America, HGA has been recognized as an emerging disease in several regions of the world in recent decades. Most available data comes from case reports, case series and retrospective studies, while prospective studies and clinical trials are largely lacking. To obtain a clearer picture of the currently known epidemiologic distribution, clinical and paraclinical presentation, diagnostic aspects, complications, therapeutic aspects, and outcomes of HGA, we systematically reviewed the literature and analyzed and summarized the data. Cases of HGA are reported from all continents except from Antarctica. HGA primarily presents as an unspecific febrile illness (88.5% of the cases) often accompanied by thrombocytopenia (71.8% of the cases), abnormal liver injury tests (66.7% of the cases), and leukopenia (49.8% of the cases). Although we found complications reported in a total of 40.5% of the reviewed cases and severe and even life-threatening complications are not infrequent (e.g. acute renal failure 9.8%, multi organ failure 7.5%, ARDS 6.3%, a.o.), sequelae are rare (2.1% of the cases) and lethality is low (3.0% of the cases). Treatment with doxycycline shows a rapid response, with the fever subsiding in the majority of patients within one day of starting treatment. Unlike in human monocytotropic ehrlichiosis (HME), reports of opportunistic infections complicating HGA are rare. HGA during pregnancy does not appear to be associated with unfavorable outcomes. In addition, our analysis provides some evidence that HGA may differ in clinical aspects and laboratory characteristics in different regions of the world. Overall, the data analyzed indicates a non-negligible bias in reporting/publication, so a certain degree of caution is required when generalizing the data.

Human monocytotropic ehrlichiosis-A systematic review and analysis of the literature

Human monocytotropic ehrlichiosis (HME) is a tick-borne bacterial infection caused by Ehrlichia chaffeensis. Most available data come from case reports, case series and retrospective studies, while prospective studies and clinical trials are largely lacking. To obtain a clearer picture of the currently known epidemiologic distribution, clinical and paraclinical presentation, diagnostic aspects, complications, therapeutic aspects, and outcomes of HME, we systematically reviewed the literature and analyzed and summarized the data. Cases of HME are almost exclusively reported from North America. Human infections due to other (non-chaffeensis) Ehrlichia spp. are rare. HME primarily presents as an unspecific febrile illness (95% of the cases), often accompanied by thrombocytopenia (79.1% of the cases), leukopenia (57.8% of the cases), and abnormal liver function tests (68.1% of the cases). Immunocompromized patients are overrepresented among reviewed HME cases (26.7%), which indicates the role of HME as an opportunistic infection. The incidence of complications is higher in immunocompromized compared to immunocompetent cases, with ARDS (34% vs 19.8%), acute renal failure (34% vs 15.8%), multi organ failure (26% vs 14.9%), and secondary hemophagocytic lymphohistiocytosis (26% vs 14.9%) being the most frequent reported. The overall case fatality is 11.6%, with a significant difference between immunocompetent (9.9%) and immunocompromized (16.3%) cases, and sequelae are rare (4.2% in immunocompetent cases, 2.5% in immunocompromised cases).

Deleterious effects of a combination therapy using fluoroquinolones and tetracyclines for the treatment of Japanese spotted fever: a retrospective cohort study based on a Japanese hospital database

OBJECTIVES

Tetracyclines are the standard treatment for rickettsiosis, including Japanese spotted fever (JSF), a tick-borne rickettsiosis caused by Rickettsia japonica. While some specialists in Japan advocate combining fluoroquinolones with tetracyclines for treating JSF, the negative aspects of combination therapy have not been thoroughly evaluated. Whether fluoroquinolones should be combined with tetracyclines for JSF treatment is controversial. The study aimed to evaluate the disadvantages of fluoroquinolones combined with tetracyclines for JSF treatment.

METHODS

This retrospective cohort study was conducted using a Japanese database comprising claims data from April 2008 to December 2020. The combination therapy group (tetracyclines and fluoroquinolones) was compared with the monotherapy group (tetracycline only) regarding mortality and the incidence of complications.

RESULTS

A total of 797 patients were enrolled: 525 received combination therapy, and 272 received monotherapy. The adjusted odds ratio (OR) for mortality was 2.30 [95% confidence interval (CI): 0.28-18.77] in the combination therapy group with respect to the monotherapy group. According to the subgroup analysis, patients undergoing combination therapy with ciprofloxacin experienced higher mortality rates compared with those receiving monotherapy (adjusted OR = 25.98, 95% CI = 1.71-393.75). Additionally, 27.7% of the combination therapy group received NSAIDs concurrently with fluoroquinolones. The combination therapy with NSAIDs group was significantly more likely to experience convulsions than the monotherapy without NSAIDs group (adjusted OR: 5.44, 95% CI: 1.13-26.30).

CONCLUSIONS

This study found no evidence that combination therapy improves mortality outcomes and instead uncovered its deleterious effects. These findings facilitate a fair assessment of combination therapy that includes consideration of its disadvantages.

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.

The first record of an established population of Amblyomma maculatum (Acari: Ixodidae) in New Jersey, USA

Amblyomma maculatum Koch, the Gulf Coast tick, is expanding northward from its original range in the southeastern United States. In 2013, its most northern collection was in Delaware. Amblyomma maculatum has since been found in Connecticut, Illinois, and New York. It is the vector of the human pathogen Rickettsia parkeri, the causative agent of R. parkeri rickettsiosis. We report the first finding of an established population of A. maculatum in Salem County, NJ, with a R. parkeri infection prevalence rate of 23.8%. Our finding of A. maculatum is consistent with other recent findings in the northeastern United States in that specimens were found in open areas devoid of tree canopy. This discovery demonstrates the importance of tick surveillance in order to identify expanding tick populations and the pathogens they may transmit.

A Mini-Review of Diagnostic Methods for the Antigen and Antibody Detection of Rocky Mountain and Brazilian Spotted Fever

Rocky Mountain or Brazilian spotted fever, caused by Rickettsia rickettsii, is a fulminant, seasonal, and neglected disease that occurs in focal points of North America and South America. Its rapid detection is essential for the better prognosis and survival rate of infected individuals. However, disease diagnosis still faces challenges as the accuracy of many of the available laboratory tests fluctuates. This review aimed to analyze methods for antibody or antigen detection, their gaps, and their evolution over time. A search was conducted to find all studies in the Pubmed database that described the antibody or antigen detection of R. rickettsii infections. Initially, a total of 403 articles were screened. Of these articles, only 17 fulfilled the pre-established inclusion criteria and were selected. Among the different methods applied, the IFA technique was the one most frequently found in the studies. However, it presented varied results such as a low specificity when using the indirect method. Other techniques, such as ELISA and immunohistochemistry, were also found, although in smaller numbers and with their own limitations. Although some studies showed promising results, there is a pressing need to find new techniques to develop a rapid and effective diagnosis of R. rickettssi infection.

Assessing the value and knowledge gains from an online tick identification and tick-borne disease management course for the Southeastern United States

BACKGROUND

Tick-borne diseases are a growing public health threat in the United States. Despite the prevalence and rising burden of tick-borne diseases, there are major gaps in baseline knowledge and surveillance efforts for tick vectors, even among vector control districts and public health agencies. To address this issue, an online tick training course (OTTC) was developed through the Southeastern Center of Excellence in Vector-Borne Diseases (SECOEVBD) to provide a comprehensive knowledge base on ticks, tick-borne diseases, and their management.

METHODS

The OTTC consisted of training modules covering topics including tick biology, tick identification, tick-borne diseases, and public health, personal tick safety, and tick surveillance. The course was largely promoted to vector control specialists and public health employees throughout the Southeastern US. We collected assessment and survey data on participants to gauge learning outcomes, perceptions of the utility of knowledge gained, and barriers and facilitators to applying the knowledge in the field.

RESULTS

The OTTC was successful in increasing participants' baseline knowledge across all course subject areas, with the average score on assessment increasing from 62.6% (pre-course) to 86.7% (post-course). More than half of participants (63.6%) indicated that they would definitely use information from the course in their work. Barriers to using information identified in the delayed assessment included lack of opportunities to apply skills (18.5%) and the need for additional specialized training beyond what the OTTC currently offers (18.5%), while the main facilitator (70.4%) for applying knowledge was having opportunities at work, such as an existing tick surveillance program.

CONCLUSIONS

Overall, this OTTC demonstrated capacity to improve knowledge in a necessary and underserved public health field, and more than half of participants use or plan to use the information in their work. The geographic reach of this online resource was much larger than simply for the Southeastern region for which it was designed, suggesting a much broader need for this resource. Understanding the utility and penetrance of training programs such as these is important for refining materials and assessing optimal targets for training.

Rocky Mountain spotted fever is a neglected tropical disease in Latin America

Rocky Mountain spotted fever (RMSF), a severe and extraordinarily lethal infectious disease, has emerged as a widespread public health crisis among predominantly vulnerable populations in several countries of Latin America, particularly evident in northern Mexico. Historically, RMSF has gained less attention than many other tropical infectious diseases, resulting in insufficient allocations of resources and development of capabilities for its prevention and control in endemic regions. We argue that RMSF fulfills accepted criteria for a neglected tropical disease (NTD). The relative neglect of RMSF in most Latin American countries contributes to disparities in morbidity and mortality witnessed in this region. By recognizing RMSF as an NTD, an increased public policy interest, equitable and more appropriate allocation of resources, scientific interest, and social participation can ameliorate the impact of this potentially treatable disease, particularly in vulnerable populations.

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 mutation associated with resistance to synthetic pyrethroids is widespread in US populations of the tropical lineage of Rhipicephalus sanguineus s.l

The brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.), is an important vector for Rickettsia rickettsii, causative agent of Rocky Mountain spotted fever. Current public health prevention and control efforts to protect people involve preventing tick infestations on domestic animals and in and around houses. Primary prevention tools rely on acaricides, often synthetic pyrethroids (SPs); resistance to this chemical class is widespread in ticks and other arthropods. Rhipicephalus sanguineus s.l. is a complex that likely contains multiple unique species and although the distribution of this complex is global, there are differences in morphology, ecology, and perhaps vector competence among these major lineages. Two major lineages within Rh. sanguineus s.l., commonly referred to as temperate and tropical, have been documented from multiple locations in North America, but are thought to occupy different ecological niches. To evaluate potential acaricide resistance and better define the distributions of the tropical and temperate lineages throughout the US and in northern Mexico, we employed a highly multiplexed amplicon sequencing approach to characterize sequence diversity at: 1) three loci within the voltage-gated sodium channel (VGSC) gene, which contains numerous genetic mutations associated with resistance to SPs; 2) a region of the gamma-aminobutyric acid-gated chloride channel gene (GABA-Cl) containing several mutations associated with dieldrin/fipronil resistance in other species; and 3) three mitochondrial genes (COI, 12S, and 16S). We utilized a geographically diverse set of Rh sanguineus s.l. collected from domestic pets in the US in 2013 and a smaller set of ticks collected from canines in Baja California, Mexico in 2021. We determined that a single nucleotide polymorphism (T2134C) in domain III segment 6 of the VGSC, which has previously been associated with SP resistance in Rh. sanguineus s.l., was widespread and abundant in tropical lineage ticks (>50 %) but absent from the temperate lineage, suggesting that resistance to SPs may be common in the tropical lineage. We found evidence of multiple copies of GABA-Cl in ticks from both lineages, with some copies containing mutations associated with fipronil resistance in other species, but the effects of these patterns on fipronil resistance in Rh. sanguineus s.l. are currently unknown. The tropical lineage was abundant and geographically widespread, accounting for 79 % of analyzed ticks and present at 13/14 collection sites. The temperate and tropical lineages co-occurred in four US states, and as far north as New York. None of the ticks we examined were positive for Rickettsia rickettsii or Rickettsia massiliae.

Newly Recognized Spotted Fever Group Rickettsia as Cause of Severe Rocky Mountain Spotted Fever-Like Illness, Northern California, USA

The incidence of spotted fever group (SFG) rickettsioses in the United States has tripled since 2010. Rocky Mountain spotted fever, the most severe SFG rickettsiosis, is caused by Rickettsia rickettsii. The lack of species-specific confirmatory testing obfuscates the relative contribution of R. rickettsii and other SFG Rickettsia to this increase. We report a newly recognized rickettsial pathogen, Rickettsia sp. CA6269, as the cause of severe Rocky Mountain spotted fever-like illness in 2 case-patients residing in northern California. Multilocus sequence typing supported the recognition of this pathogen as a novel Rickettsia genotype most closely related to R. rickettsii. Cross-reactivity observed for an established molecular diagnostic test indicated that Rickettsia sp. CA6269 might be misidentified as R. rickettsii. We developed a Rickettsia sp. CA6269-specific real-time PCR to help resolve this diagnostic challenge and better characterize the spectrum of clinical disease and ecologic epidemiology of this pathogen.