Tick-borne Encephalitis in Childhood: Rare or Missed?

Magnus E. A. Hansson, MD; Claes Örvell, MD, PhD; Mona-Lisa Engman, MD, PhD; Katarina Wide, MD, PhD; Lars Lindquist, MD, PhD; Karl-Johan Lidefelt, MD, PhD; Mikael Sundin, MD, PhD

Disclosures

Pediatr Infect Dis J. 2011;30(4):355-357. 

In This Article

Discussion

In the present study, anti-TBE serologies were consistent with the diagnosis in 5.5% of patients <16 years. Since the symptomatology is nonspecific, there is reason to believe that children and adults may elude diagnosis. Hence, 26.6% of patients with exclusively positive anti-TBE IgG had no medical history of flavivirus infection (N.B., TBEV is the only local Flavivirus) and were nonimmunized against flaviviruses. False positive anti-TBE serologies as an explanation in all these patients seem unlikely. Because the pitfalls and risk of bias when evaluating medical history retrospectively up to 6 years later, it can be argued that a significant number of patients might elude diagnosis due to subclinical infections.

The number of preschool children in this study is small. Since, according to the literature, childhood TBE is a rare disease particularly in preschool children,[1,3,6,11] there is reason to suspect too infrequent consideration of the diagnosis. This is corroborated by the fact that during 2008, serologies (at our hospital) indicating Borrelia burgdorferi infection were 5 times more common (25.9% vs. 5.7%) in preschool children than schoolchildren and adults (C. Örvell, MD, PhD, unpublished data, 2010). Therefore, young children are evidently more exposed to ticks than can be concluded from the anti-TBE serologies. Whether this is a result of a better clinical awareness of B. burgdorferi infections than TBE infections in childhood needs to be elucidated.

Our data indicate that the clinical presentation and course of childhood TBE contrast in several aspects with the disease seen in adults. Symptoms are vague and nonspecific, and difficulties in verbalization of symptoms further emphasize the diagnostic challenge in children. The most prominent symptom was headache, reported in 60% of the preschool children compared with 74.3% to 85.2% in older individuals. This contrasts with previous studies where headache was reported in >90% children and adults.[3–5,8,11] Furthermore, the biphasic course—a hallmark of TBE—was seen less frequently in preschool children than in older individuals.[3–5,11] Generally, adults tended to be more affected and display motor abnormalities to a greater extent than children, as described by others.[1,3,5] Again this indicates that childhood TBE is either characterized by vague symptoms easily eluding recognition or that symptoms usually described for adolescents/adults may be absent.

It has been hypothesized that TBEV induces a more pronounced encephalitic picture in adults than in children.[5,11,12] This is corroborated by our findings of more frequent cognitive dysfunction, motor abnormalities, and elevated CSF albumin concentrations in adults. The medical history, clinical findings, and laboratory data indicate that the childhood TBE is a nonspecific inflammatory disease with a restricted encephalitic profile. Such an age-dependant symptomatology, also seen in other viral diseases, eg, Epstein-Barr virus and varicella-zoster virus infections, shows that immune responses can be different in children and adults.[13,14]

The diagnostic problems could be partly overcome by careful medical history and clinical examination. A comparison of children with and without TBE showed that biphasic course, vertigo/balance problems, and neck stiffness should prompt the clinician to consider TBE. In view of severe clinical courses of TBE in adults and the poorly described risk of sequelae in childhood TBE,[1,3,4,7,8] there is reason to believe that children, in whom the diagnosis is probably missed to a large extent, would benefit from increased vigilance among medical care providers. Anti-TBE serologies should be performed more frequently because of the vague symptomatology and sparse clinical findings. Prospective studies are warranted to determine the incidence as well as morbidity and long-term consequences of childhood TBE.

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