Sunday, September 24, 2023
|
Characteristic |
Confirmed, n = 166 |
Possible, n = 134 |
p value |
|---|---|---|---|
| Median age, y (range)† | 56 (4–86) | 50 (1–86) | 0.03‡ |
| Categorical age | |||
| <18 | 15/166 (9) | 5/134 (4) | |
| 18–65 | 95/166 (57) | 101/134 (75) | 0.004 |
| >65 | 56/166 (34) | 28/134 (21) | |
| Sex | |||
| M | 92/166 (56) | 65/134 (49) | 0.23 |
| F | 74/166 (44) | 69/134 (51) | |
| Year of illness onset§ | |||
| 2013 | 8/165 (5) | 0/132 (0) | |
| 2014 | 9/165 (5) | 1/132 (1) | |
| 2015 | 1/165 (1) | 8/132 (6) | |
| 2016 | 16/165 (10) | 10/132 (8) | <0.0001¶ |
| 2017 | 56/165 (34) | 22/132 (17) | |
| 2018 | 38/165 (23) | 44/132 (34) | |
| 2019 | 37/165 (22) | 46/132 (35) | |
Table 1. Demographic characteristics for confirmed and possible cases of hard tick relapsing fever caused by Borrelia miyamotoi identified by public health surveillance, United States, 2013–2019*
*Values are no. positive/no. tested (%) unless indicated otherwise.
†Missing information for 25 persons.
‡By Wilcoxon rank-sum test.
§Missing information for 4 persons.
¶By Fisher exact test.
|
Characteristic |
Confirmed, n = 165 |
Possible, n = 133 |
p value |
|---|---|---|---|
| Hospitalized | 20 (12) | 19 (14) | 0.61 |
| Median duration of illness, d† (IQR) | 3 (2–7) | 9 (3–29) | 0.03 |
| Required symptoms | |||
| Fever | 157 (95) | 108 (81) | <0.0001 |
| Chills | 115 (70) | 87 (65) | 0.27 |
| Supporting signs and symptoms | |||
| Headache | 118 (72) | 96 (72) | 0.85 |
| Myalgia | 104 (63) | 94 (71) | 0.20 |
| Arthralgia | 79 (48) | 84 (63) | 0.02 |
| Malaise/fatigue | 125 (76) | 99 (74) | 0.55 |
| Rash | 21 (13) | 28 (21) | 0.06 |
| Abdominal pain | 16 (10) | 27 (20) | 0.01 |
| Nausea | 55 (33) | 36 (27) | 0.26 |
| Vomiting | 23 (14) | 15 (11) | 0.44 |
| Diarrhea | 8 (5) | 17 (13) | 0.01 |
| Dizziness | 26 (16) | 33 (25) | 0.06 |
| Confusion | 7 (4) | 24 (18) | <0.0001 |
| Photophobia | 8 (5) | 11 (8) | 0.29 |
| Leukopenia‡ | 31 (46) | 8 (22) | 0.02 |
| Thrombocytopenia§ | 40 (58) | 9 (25) | 0.001 |
| Increased levels of aminotransferases¶ | 27 (45) | 13 (36) | 0.41 |
| Other symptoms | |||
| Recurring fevers | 37 (22) | 47 (35) | 0.01 |
| Shortness of breath | 5 (3) | 14 (11) | 0.01 |
| Cough | 15 (9) | 10 (8) | 0.53 |
| Anorexia | 32 (19) | 26 (20) | 0.99 |
| Jaundice | 2 (1) | 4 (3) | 0.21 |
| Lymphadenopathy | 0 (0) | 0 (0) | NA |
| Cognitive impairment/mood disturbance | 7 (4) | 21 (16) | 0.0004 |
| Meningitis/encephalitis | 0 (0) | 5 (4) | 0.01 |
| Neutropenia | 6 (4) | 2 (2) | 0.11 |
| Abnormal chest radiograph | 11 (7) | 2 (2) | 0.04 |
Table 2. Clinical and laboratory findings for persons who have confirmed and possible hard tick relapsing fever caused by Borrelia miyamotoi among reported cases with available laboratory findings identified by public health surveillance, United States, 2013–2019*
*Values are no. (%) unless indicated otherwise. IQR, interquartile range; NA, not available.
†Defined as duration from symptom onset to first seeking medical care.
‡Information regarding a patient’s leukocyte count was available for 68 confirmed and 37 possible cases.
§Information regarding a patient’s platelet count was available for 69 confirmed and 36 possible cases.
¶Information regarding a patient’s alanine and aspartate aminotransferase levels was available for 60 confirmed and 36 possible cases.
|
Characteristic |
Confirmed, n = 166† |
Possible, n = 134 |
|---|---|---|
| PCR results | ||
| Detected | 162/164 (99) | 0/5 (0) |
| Not detected | 0/164 (0) | 5/5 (100) |
| Serologic analysis results | ||
| Single IgM alone | ||
| Positive | 2/2 (100) | 36/127 (28) |
| Negative | 0/2 (0) | 89/127 (70) |
| Indeterminate | 0/2 (0) | 2/127 (2) |
| Single IgG alone | ||
| Positive | 0/2 (0) | 111/127 (87) |
| Negative | 2/2 (100) | 16/127 (13) |
| Indeterminate | 0/2 (0) | 0/127 (0) |
| Single combined IgM/IgG | ||
| Positive | 1/2 (50) | 6/7 (86) |
| Negative | 0/2 (0) | 1/7 (14) |
| Indeterminate | 1/2 (50) | 0/7 (0) |
| Paired serologic samples | ||
| ≥4-fold change in titer | 1/1 (100) | 0/18 (0) |
| <4-fold change in titer | 0/1 (0) | 18/18 (100) |
Table 3. Diagnostic results for confirmed and possible cases of hard tick relapsing fever caused by Borrelia miyamotoi reported by public health surveillance, United States, 2013–2019*
*Values are no. positive/no. tested (%).
†Missing diagnostic information for 2 cases.
Physicians - maximum of 1.00 AMA PRA Category 1 Credit(s)™
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This activity is intended for primary care clinicians, infectious disease specialists, and other healthcare professionals who treat and manage patients who might develop vector-borne illness.
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Borrelia miyamotoi, transmitted by Ixodes spp. ticks, was recognized as an agent of hard tick relapsing fever in the United States in 2013. Nine state health departments in the Northeast and Midwest have conducted public health surveillance for this emerging condition by using a shared, working surveillance case definition. During 2013–2019, a total of 300 cases were identified through surveillance; 166 (55%) were classified as confirmed and 134 (45%) as possible. Median age of case-patients was 52 years (range 1–86 years); 52% were male. Most cases (70%) occurred during June–September, with a peak in August. Fever and headache were common symptoms; 28% of case-patients reported recurring fevers, 55% had arthralgia, and 16% had a rash. Thirteen percent of patients were hospitalized, and no deaths were reported. Ongoing surveillance will improve understanding of the incidence and clinical severity of this emerging disease.
Tickborne diseases are an increasing public health problem, accounting for ≈75% of reported vectorborne illnesses in the United States[1‒3]. Continued discovery of new tickborne pathogens in recent years suggests they remain an underrecognized cause of human illness[4–6]. Borrelia miyamotoi is a gram-negative spirochete transmitted by Ixodes spp. ticks[7–9] that was initially identified in ticks in Japan during 1995[7]. It was recognized as a cause of human illness in Russia during 2011[10] and in the United States during 2013[11]. Human infection has since been detected throughout the Holarctic region[10,12–17].
Phylogenetically, B. miyamotoi is a relapsing fever group Borrelia[18]. Diseases caused by this diverse group of spirochetes are differentiated by their vector, such as louseborne relapsing fever, transmitted by body lice, and tickborne relapsing fever or soft tick relapsing fever, transmitted by soft-bodied (argasid) ticks in several areas, including the western United States[19]. B. miyamotoi is an agent of hard tick relapsing fever (HTRF), although resulting illness has also been referred to as B. miyamotoi disease. In the United States, B. miyamotoi is transmitted by I. scapularis ticks in the Northeast and Midwest[20,21] and by I. pacificus ticks on the Pacific Coast[22]. Those tick species also transmit the causative agents of Lyme disease[23], anaplasmosis[24], babesiosis[25], Powassan virus disease[26], and a form of ehrlichiosis[27]. Data from tick testing indicate that the geographic range of B. miyamotoi is similar to that of those pathogens[28,29].
The incidence of HTRF caused by B. miyamotoi and its public health role are largely unknown. In the United States, prevalence of B. miyamotoi in Ixodes spp. ticks is relatively low, but consistent across geographic regions at ≈2%[3,29]. A seroprevalence evaluation conducted in several states in the northeastern United States in 2018 suggested that 2.8% of persons might have evidence of previous infection, compared with 11% of persons who had evidence of previous Lyme disease[30]. Data from previous case series suggest that HTRF caused by B. miyamotoi most often manifests as a nonspecific febrile illness. Among identified cases, fever, myalgia, arthralgia, and headache are common, but recurring fevers similar to those documented in patients who have soft tick relapsing fever are relatively uncommon (4%–11% of total)[10,17]. Immunocompromised persons who have HTRF might have more severe symptoms, including meningoencephalitis[11,16,31].
Specific laboratory diagnosis of B. miyamotoi infection is achieved through PCR detection of B. miyamotoi DNA[10,17,32]. Serologic reactivity to surface proteins, especially glycerophosphodiester phosphodiesterase (GlpQ), is also used, but reactivity is not specific to B. miyamotoi infection or HTRF[33,34]. GlpQ is found in all relapsing fever group borreliae but not in the B. burgdorferi sensu lato species that cause Lyme disease[34]. However, GlpQ cannot distinguish between B. miyamotoi infection and infections caused by other relapsing fever group Borrelia spp., including agents of soft tick relapsing fever. In addition, related GlpQ proteins are found in common bacterial pathogens, such as Haemophilus influenzae and Escherichia coli, further reducing specificity of those serologic assays[34].
After initial cases of HTRF were identified in the United States, several states that had a high incidence of Lyme disease and other Ixodes-transmitted illnesses initiated public health surveillance to clarify the epidemiology of this novel tickborne condition. We summarize available information on HTRF as ascertained through public health surveillance efforts in the United States beginning in 2013.
