Patterns Testing for Tick-Borne Diseases and Implications for Surveillance in the Southeastern US

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.

Tick HRF-dependent ferroptosis pathway to promote tick acquisition of Babesia microti

B. microti is a tick-transmitted zoonotic erythrocytic intracellular parasite. Ferroptosis is an iron-dependent form of programmed cell death that affects pathogen replication in the host. Currently, there is limited research concerning the effect of tick ferroptosis on Babesia infection and the underlying mechanism of action. The present study used a B. microti -mouse- Haemaphysalis longicornis infection model in which nymphs fed on the blood of B. microti-infected mice. The midgut divalent iron (p<0.01) and reactive oxygen species (ROS) (p<0.05) levels were significantly elevated in infected ticks, and transmission electron microscopy (TEM) showed that mitochondrial ridges were absent or decreased in size. Downregulation of ferritin 1 and glutathione peroxidase 4 (GPX4) in ticks infected with B. microti suggests that these changes promote ferroptosis. In vivo studies demonstrated that the ferroptosis promoter Erastin increased B. microti load (p<0.05), while the inhibitor Ferrostatin-1 effectively decreased load (p<0.01). Tick histamine-releasing factor (HRF), a protein related to the antioxidant system, was downregulated in infected nymphs compared with uninfected nymphs (p<0.05), and interference with HRF promoted tick acquisition of B. microti (p<0.001). Transcriptomic analyses showed that HRF interference promotes tick ferroptosis by downregulating ferritin 1 and GPX4. Meanwhile, interference with tick HRF molecules showed increased divalent iron and ROS and decreased mitochondrial ridges compared with controls. These findings highlight the critical role of tick HRF molecules in regulating ferroptosis and acquisition of B. microti, thereby providing important insights for a deeper understanding of the tick-Babesia interaction.

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.

A customizable multiplex protein microarray for antibody testing and its application for tick-borne and other infectious diseases

Tick-borne infections are the most common vector-borne diseases in the USA. Ticks harbor and transmit several infections with Lyme disease being the most common tickborne infection in the US and Europe. Lack of awareness about tick populations, specific diagnostic tests, and overlapping signs and symptoms of tick-borne infections can often lead to misdiagnosis affecting treatment and the prevalence data reported especially for non-Lyme tick-borne infections. The diagnostic tests currently available for tick-borne diseases are severely limited in their ability to provide accurate results and cannot detect multiple pathogens in a single run. The multiplex protein microarray developed at Vibrant was designed to detect multiple serological antibodies thereby detecting exposure to multiple pathogens simultaneously. Our microarray in its present form can accommodate 400 antigens (molecules that can bind to specific antibodies) and can multiplex across antigen types, whole cell lysates, recombinant proteins, and peptides. A designed array containing multiple antigens of several microbes including Borrelia burgdorferi, the Lyme disease spirochete, was manufactured and evaluated. The immunoglobulin M (IgM) and G (IgG) responses against several tick-borne microbes and other infectious agents were analyzed for analytical and clinical performance. The microarray improved IgM and IgG sensitivities and specificities of individual microbes when compared with the respective gold standards. The testing was also performed in a single run in comparison to multiple runs needed for comparable testing standards. In summary, our study presents a flexible multiplex microarray platform that can provide quick results with high sensitivity and specificity for evaluating exposure to varied infectious agents especially tick-borne pathogens.

Changes in the Seroprevalence of Tick-Borne Rickettsia and Ehrlichia Among Soldiers-Fort Liberty, North Carolina, 1991-2019

We obtained samples from the Department of Defense Serum Repository from soldiers who were stationed at Fort Liberty, North Carolina, between 1991 and 2019 to assess temporal trends in tick-borne rickettsiosis and ehrlichiosis. Serological evidence of infection was common, with nearly 1 in 5 (18.9%) demonstrating antibodies. We observed significant decreases in Rickettsia seroprevalence (adjusted odds ratio [aOR], 0.42 [95% CI, .27-.65], P = .0001) while over the same period Ehrlichia seroprevalence, albeit less common, nearly doubled (aOR, 3.61 [95% CI, 1.10-13.99], P = .048). The increase in Ehrlichia seroprevalence likely reflects increased transmission resulting from the expanding geographic range of the lone star tick.

Neurological manifestations of ehrlichiosis among a cohort of patients: prevalence and clinical symptoms

BACKGROUND

Ehrlichiosis is a potentially fatal tick-borne disease that can progress to involve the central nervous system (CNS) (i.e., neuro-ehrlichiosis), particularly in cases where diagnosis and treatment are delayed. Despite a six-fold national increase in the incidence of ehrlichiosis over the past 20 years, recent data on the prevalence and manifestations of neuro-ehrlichiosis are lacking.

METHODS

We conducted a retrospective chart review of all patients tested for ehrlichiosis at University of North Carolina Health facilities between 2018 and 2021 and identified patients who met epidemiological criteria for ehrlichiosis as established by the Council of State and Territorial Epidemiologists and employed by the Centers for Disease Control and Prevention. We estimated the prevalence of neurological symptoms and described the spectrum of neurological manifestations in acute ehrlichiosis, documenting select patient cases in more detail in a case series.

RESULTS

Out of 55 patients with confirmed or probable ehrlichiosis, five patients (9.1%) had neurologic symptoms, which is notably lower than previous estimates. Neurological presentations were highly variable and included confusion, amnesia, seizures, focal neurological deficits mimicking ischemic vascular events, and an isolated cranial nerve palsy, though all patients had unremarkable neuroimaging at time of presentation. All but one patient had risk factors for severe ehrlichiosis (i.e., older age, immunosuppression).

CONCLUSIONS

Neuro-ehrlichiosis may lack unifying patterns in clinical presentation that would otherwise aid in diagnosis. Clinicians should maintain a high index of suspicion for neuro-ehrlichiosis in patients with acute febrile illness, diverse neurological symptoms, and negative neuroimaging in lone star tick endemic regions.

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.

The clinical epidemiology, management, and outcomes of patients diagnosed with encephalitis in North Carolina, 2015-2020

IMPORTANCE

Despite the relatively high mortality and the difficulty in diagnosis, nearly one-third of patients hospitalized with a documented diagnosis of encephalitis did not undergo a lumbar puncture (LP). When an LP was performed, pathogen-specific testing was greatly underutilized. Infectious etiologies were most common, but over 40% of cases were idiopathic at discharge. These findings suggest that there is a substantial opportunity to improve the quality of care through more accurate and timely diagnosis.

Impact of the COVID-19 pandemic on delays in diagnosis and treatment of tick-borne diseases endemic to southeastern USA

BACKGROUND

The Coronavirus disease 2019 (COVID-19) pandemic was marked by an increase in diagnosis and treatment delays for a range of medical conditions. Yet the impact of the pandemic on the management of tick-borne diseases, which frequently manifest as an acute febrile illness similar to COVID-19, has not been well described.

METHODS

In this retrospective cohort study of patients with suspected tick-borne disease attending the University of North Carolina Health facilities, we compared the timeliness of diagnosis and treatment in a "pre-COVID" period (March 2019 to February 2020) and a "post-COVID" period (March 2020 to February 2021). Participants included patients with an ICD-10 diagnosis code of spotted fever group rickettsiosis or ehrlichiosis and a positive Rickettsia rickettsii or Ehrlichia indirect immunofluorescence assay immunoglobulin G antibody test result. Of the 897 patients who had an eligible diagnosis, 240 (26.8%) met the inclusion criteria. The main outcome was time from initial presentation to definitive diagnosis and treatment.

RESULTS

During the 2-year study period, 126 (52.5%) patients were grouped in the pre-COVID period and 114 (47.5%) were grouped in the post-COVID period; 120 (50.0%) were female; and 139 (57.9%) were aged > 50 years. Comparing the post-COVID to the pre-COVID period, the adjusted odds ratio (aOR) for delay in treatment > 0 days was 1.81 (95% confidence interval [CI] 1.07-3.07, P = 0.03), and for a treatment delay > 7 days, 1.65 (95% CI 0.94-2.90, P = 0.08). The odds of a delay in diagnosis were similar for patients in the post- and pre-COVID periods, with an aOR of 1.61 (95% CI 0.96-2.72, P = 0.07) for delays > 0 days, and aOR of 1.72 (95% CI 0.99-3.00, P = 0.05) for delays > 7 days.

CONCLUSIONS

The odds of a delay in treatment > 0 days were significantly higher in the post-COVID period than in the pre-COVID period. However, the odds of a delay in treatment > 7 days, or a delay in diagnosis, were similar between these two periods. Shifts in care-seeking, alternative care delivery models and prioritization of COVID-19 may contribute to diminished timeliness of treatment for patients with tick-borne diseases.

Under-diagnosis of vector-borne diseases among individuals suspected of having Scrub Typhus in South Korea

Due to environmental and ecological changes and suitable habitats, the occurrence of vector-borne diseases is increasing. We investigated the seroprevalence of four major vector-borne pathogens in human patients with febrile illness who were clinically suspected of having Scrub Typhus (ST) caused by Orientia tsutsugamushi. A total of 187 samples (182 patient whole blood and sera samples, including 5 follow-up) were collected. Antibodies to Anaplasma phagocytophilum, Ehrlichia chaffeensis, Borrelia burgdorferi, and Bartonella henselae were tested by using indirect immunofluorescence assays. Molecular diagnoses were performed using real-time PCR. Of the 182 cases, 37 (20.3%) cases were designated as confirmed cases of ST, and the remaining 145 (79.7%) cases as other febrile diseases (OFDs). The seroprevalence of A. phagocytophilum, E. chaffeensis, B. burgdorferi, and B. henselae was 51.4% (19/37), 10.8% (4/37), 86.5% (32/37), and 10.8% (4/37) among the ST group, and 42.8% (62/145), 10.4% (19/145), 57.7% (105/145), and 15.9% (29/145) among the OFD group, respectively. There were no significant differences in the seroprevalence between the ST and the OFD groups. Considering the co-occurrence, 89.0% (162/182) had at least one antibody to tick-borne pathogens, 37.0% (60/162) were positive for two pathogens, 17.3% (28/162) for three pathogens, and 6.2% (10/162) for four pathogens. In real-time PCR, O. tsutsugamushi was positive in 16 cases [15 (40.5%) in ST group and 1 (2.2%) in OFD group], and the four other pathogens were negative in all cases except one confirmed as anaplasmosis. In evaluating the five follow-up samples, the appearance of new antibodies or an increase in the pre-existing antibody titers was detected. Our data highlighted that acute febrile illness and manifestations suggestive of a vector-borne infection must be recognized and further considered for coinfections in clinical practice and the laboratory.