IMPORTANCE Tick-borne diseases (TBD), including spotted fever group rickettsiosis (SFGR), ehrlichiosis, and, increasingly, Lyme disease, represent a substantial public health concern throughout much of the southeastern United States. Yet, there is uncertainty about the epidemiology of these diseases because of pitfalls in existing diagnostic test methods. OBJECTIVETo examine patterns of diagnostic testing and incidence of TBD in a large, academic health care system. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional study included diagnostic test resultsfor TBD at UNC Health, a large academic health care system with inpatient and outpatient facilities, from January 1, 2017, to November 30, 2020. Participants included all individuals seeking routine care at UNC Health facilities who had testing for SFGR, ehrlichiosis, or Lyme disease performed during the study period. MAIN OUTCOMES AND MEASURESRates of test positivity, testing completeness, and incidence of TBD. RESULTS During the 4-year study period, 11 367 individuals (6633 [58.4%] female; 10 793 [95%] non-Hispanic individuals and 8850 [77.9%] White individuals; median [IQR] age, 53 [37-66] years) were tested for TBD. Among the 20 528 diagnostic tests performed, 47 laboratory-confirmed, incident cases of SFGR, 27 cases of ehrlichiosis, and 76 cases of Lyme were confirmed, representing incidence rates of 4.7%, 7.1%, and 0.7%, respectively. However, 3984 of SFGR tests (79.3%) and 3606 of Ehrlichia tests (74.3%) lacked a paired convalescent sample. Of 20 528 tests, there were 11 977 tests (58.3%) for Lyme disease from 10 208 individuals, 5448 tests (26.5%) for SFGR from 4520 individuals, and 3103 tests (15.1%) for ehrlichiosis from 2507 individuals. Most striking, testing for ehrlichiosis was performed in only 55% of patients in whom SFGR was ordered, suggesting that ehrlichiosis remains underrecognized. An estimated 187 incident cases of SFGR and 309 of ehrlichiosis were potentially unidentified because of incomplete testing. CONCLUSIONS AND RELEVANCEIn this cross-sectional study, most of the patients suspected of having TBD did not have testing performed in accordance with established guidelines, which substantially limits understanding of TBD epidemiology. Furthermore, the data revealed a large discrepancy between the local burden of disease and the testing performed. These findings underscore the need to pursue more robust, active surveillance strategies to estimate the burden of TBD and distribution of causative pathogens.
Background Alpha-gal syndrome (AGS) is a recently described allergy to galactose-α-1,3-galactose, an oligosaccharide present in mammalian meat. AGS can present with angioedema, urticaria, and anaphylaxis arising 3-6 hours after ingestion, although symptoms such as gastrointestinal distress, fatigue, and arthralgias are also reported. Because AGS appears to be associated with tick bites, patients may present to Infectious Diseases (ID) clinics for evaluation. Methods We documented a series of five patients referred to the University of North Carolina ID clinic between 2020–2022 for various tick-borne infections that were found to have symptoms and laboratory testing consistent with AGS. Patients were subsequently referred to the Allergy and Immunology clinic. Results : Patients were referred to the ID clinic for persistent symptoms following positive tick-borne disease testing or presumed tick-borne infection. All patients had an elevated alpha-gal IgE and clinical presentation consistent with AGS. Common symptoms included episodic gastrointestinal distress (e.g., cramping, nausea, diarrhea), fatigue, arthralgias, and subjective cognitive impairment, but a notable absence of severe anaphylaxis. Four patients were seen by at least one non-allergy specialist prior to referral to ID. Patients reported substantial improvement in their symptoms following dietary restriction. Conclusions ID physicians should be aware of AGS as a cause of persistent, non-specific symptoms following a tick exposure or tick-borne illness. Further research is needed to determine the prevalence of alpha-gal sensitization and AGS following tick-borne bites.
Knock-down resistance (kdr) mutations in the voltage-gated sodium channel gene of Aedes species mosquitoes are biomarkers for resistance to pyrethroid insecticides. In the United States, few studies have reported kdr mutations among Aedes albopictus (Skuse) (Diptera: Culicidae) populations. In this study, we sought to compare the presence of kdr alleles among Ae. albopictus mosquitoes collected from Fort Bragg and Wake County, North Carolina. We collected 538 Ae. albopictus mosquitoes, including 156 from 4 sites at Fort Bragg, North Carolina and 382 from 15 sites in Wake County, North Carolina to compare the prevalence of kdr mutations. Of those successfully sequenced, we identified 12 (3.0%) mosquitoes with kdr mutations, all of which were attributed to variants at position 1534 within domain 3. All mutations were found in mosquitoes collected at Wake County sites; no mutations were identified in collections from Fort Bragg. There was a focus of mutations observed at the Wake County sites with approximately 92% (11 of 12) of the mosquitoes with the mutation coming from one site, where kdr mutations represented 24.4% (11 of 45) of all mosquitoes collected. We observed highly focal resistance in a suburban area of Raleigh, which may be attributable to peri-domestic mosquito control activities that involve area dispersal of pyrethroid insecticides. More robust surveillance is needed to monitor the emergence and spread of resistance.
Background Human Monocytic Ehrlichiosis is caused by infection with the bacteria Ehrlichia chaffeensis through the bite of an infected lone star tick (Amblyomma americanum). Patients infected with Human Monocytic Ehrlichiosis often present with symptoms including fever, headache, myalgia, and occasionally a macular rash. The presence of other endemic tick-borne diseases with similar symptoms, such as Rocky Mountain Spotted Fever, complicate the diagnosis of Human Monocytic Ehrlichiosis. Case presentation A patient developed a fever, diffuse myalgia, headache, and a non-productive cough 5 days after a fishing trip in late May in central North Carolina. Over the course of the illness the patient’s symptoms worsened, with arthralgia, bilateral lower extremity erythema and edema, and a developing bilateral rash on the palms. With testing that revealed elevated liver enzymes, a potential for recent tick exposure (e.g., fishing trip), presentation during tick season, and the development of a rash, Rocky Mountain Spotted Fever and Human Monocytic Ehrlichiosis were considered. The patient was prescribed a seven-day course of oral doxycycline and cefalexin, which would provide coverage from Rickettsia, Ehrlichia and gram-positive bacteria typically responsible for cellulitis. Many of the patient’s symptoms resolved or improved, although the right shoulder remained painful to active movement. The patient was prescribed another seven-day course of doxycycline due to his perceived incomplete response to the first course. Approximately 5 weeks after symptom onset (D0 + 36), the patient followed up with a provider for convalescent testing and counseling. Convalescent Ehrlichia and Rickettsia serological tests were ordered. The acute Ehrlichia serology and acute Rickettsia serology were originally non-reactive with both titers measured at < 1:64. Convalescent serology, ordered 28 days after the acute sample collection, showed a greater than four-fold increase in the Ehrlichia IgG titer (1:256), satisfying clinical and laboratory case definitions for ehrlichiosis. In follow-up, 3 weeks later (D0 + 57), the patient reported that most of his pain had subsided, though he still occasionally got shooting nerve pain when exercising. Conclusion This case of Human Monocytic Ehrlichiosis in North Carolina exemplifies the need for a knowledge of spatial epidemiological patterns and clinical manifestations in the diagnosis of tick-borne diseases.
Importance: Tick–borne diseases (TBD) including Spotted Fever Group Rickettsiosis (SFGR), ehrlichiosis, and increasingly Lyme disease represent a substantial public health concern throughout much of the Southeastern United States. Yet, there is uncertainty about the epidemiology of these diseases due to pitfalls in existing diagnostic test methodologies. Objective: To examine patterns of diagnostic testing and incidence of TBD in a large, academic healthcare system. Design: Cross–sectional study of diagnostic test results from UNC Health for the period January 1st, 2017 to November 30th, 2020. Setting: Large, academic healthcare system in central North Carolina including inpatient and outpatient facilities. Participants: All Individuals seeking routine care at UNC Health facilities who had testing for SFGR, ehrlichiosis or Lyme disease performed during the study period Measurements: Rates of test positivity, testing completeness, and incidence of TBD Results: Among the 20,528 diagnostic tests performed, we identified 47 laboratory–confirmed, incident cases of SFGR, 27 of ehrlichiosis, and 76 of Lyme, representing incidence rates of 4.7%, 7.1%, and 0.7% respectively. However, 79.3% of SFGR tests and 74.3% Ehrlichia tests lacked a paired convalescent sample. The total number of tests for Lyme disease was more than SFGR and ehrlichiosis combined, despite the relatively low incidence of disease in region. Most striking, testing for ehrlichiosis was performed in only half of patients in whom SFGR was ordered, suggesting that this disease remains underrecognized. Overall, we estimate that there were 187 incident cases of SFGR and 309 of ehrlichiosis that were not identified due to incomplete testing; a number that would drastically increase – and in the case of ehrlichiosis, nearly double – the total number of cases reported. Conclusions and Relevance: A majority of patients suspected of having TBD did not have testing performed in accordance with established guidelines, substantially limiting our understanding of TBD epidemiology. Furthermore, there appears to be a large discrepancy between the local burden of disease and the testing that is performed. These findings underscore the need to pursue more robust, active surveillance strategies to estimate the burden of TBDs and distribution of causative pathogens.
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