Page 112 - JSOM Summer 2023

An Ongoing Series

Tick-Borne Encephalitis

An Update for the Special Operations Forces Provider

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Harpreet Kaur, MD ; Akira A. Shishido, MD *

ABSTRACT
Tick-borne encephalitis (TBE) is a severe disease caused by providers should be aware of this disease entity and strongly
the tick-borne encephalitis virus (TBEV). TBEV is endemic consider the newly FDA-approved TBE vaccine when planning
throughout Eurasia and can cause persistent neurologic defi- exercises and operations in Areas of Responsibility (AORs)
cits and death. Special Operations Forces (SOF) participating with TBE-endemic countries.
in field exercises or operations in TBE-endemic countries are
at significantly increased risk of infection. Unlike Lyme disease Military History
and other tick-borne illnesses, transmission of TBEV can be
immediate, and early tick removal does not reduce the risk of TBE was first described in Austria in 1931 with the caus-
infection. While there are no virus-specific treatments avail- ative agent later isolated in Russia in 1937. Since that time,
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able, the US Food and Drug Administration (FDA) recently TBE has been documented across Eurasia, including many
approved a TBE vaccine that has yet to be incorporated into countries housing US troops and DoD beneficiaries. A re-
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formal Department of Defense (DoD) recommendations. SOF cent retrospective analysis found eight cases of TBE among
medical providers should be aware of this disease entity and servicemembers and their beneficiaries stationed in Germany
consider the TBE vaccine when planning exercises and oper- between 2006 and 2018. Of these eight cases, seven occurred
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ations in areas of responsibility (AORs) with TBE-endemic in 2017 or 2018, suggesting an increasing rate of infection. A
countries. This review serves as a refresher and update on the case report describing three of these infections (a 26-year-old
epidemiology, transmission, and management of TBE for the male Soldier, a 17-year-old male dependent, and a 7-year-old
SOF provider. female dependent) found that while all three survived, all had
persistent headaches and cognitive complaints 3–6 months af-
Keywords: Tick-borne encephalitis; tick-borne disease; vec- ter diagnosis. An updated survey described four additional
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tor; biphasic; vaccines; biodefense cases among Military Health System (MHS) beneficiaries
from 2019–2021, three of whom were active duty stationed
in Germany. These observations are consistent with large-
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scale studies suggesting a growing number of reported cases
Introduction
overall and that a significant percentage of TBE cases result
Tick-borne encephalitis (TBE) is a severe vaccine-preventable in long-term neurologic sequelae. There is likely a paucity of
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disease caused by tick-borne encephalitis virus (TBEV) trans- data describing the burden of disease among temporary duty
mitted by Ixodes species ticks. TBEV is among the most (TDY) personnel. While TBE has been a recognized threat to
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prevalent causes of arthropod-borne viral meningitis and en- force health protection for decades, US servicemembers had no
cephalitis worldwide. Many cases of TBE result in persistent FDA-approved vaccine options until 2021.
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neurologic deficits, and case fatality rates can exceed 20%.
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Servicemembers, particularly Special Operations Forces (SOF) Epidemiology/Transmission
participating in field exercises or operations in TBE-endemic
countries, are at significantly increased risk of infection. Mea- TBE is endemic to countries across the Eurasian continent
sures to prevent tick bites include standard insect precautions where the Ixodes tick vectors are present, creating the “TBE
(including use of repellents, long sleeves, permethrin-treated Belt” (Figure 1). The virus circulates between ticks and vari-
clothing, bed netting, and other gear). However, unlike Lyme ous reservoirs: ruminants, birds, rodents, horses, and humans
disease and other tick-borne illnesses, transmission of TBEV (Figure 2). Three viral subtypes from the family Flaviviridae
from a tick bite can be immediate, and early tick removal (genus Flavivirus) cause TBE: Siberian (TBEV-Sib), Far Eastern
does not reduce risk of infection. Given TBE’s potential for (TBEV-FE), and Western (TBEV-Eu). The vector for TBEV-Eu
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significant morbidity and efficient transmission, SOF medical is Ixodes Ricinus (Western, Central, and Eastern Europe). The
*Correspondence to akira.shishido@vcuhealth.org
1 Dr Harpreet Kaur is a physician affiliated with the University of Maryland Medical Center Division of Infectious Diseases, Baltimore, MD.
2 Dr Akira A. Shishido is a physician affiliated with Virginia Commonwealth University, Division of Infectious Diseases, Richmond, VA.

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