Tick Borne Encephalitis

Question 1

How many subtypes are there of TBEV? What are they?

Answer 1

5 - European, Siberian, Far Eastern, Baikalian, Himilayan

Question 2

When is TBEV most commonly transmitted in Europe?

Answer 2

Between April and November

Question 3

What are the reservoir hosts of TBEV?

Answer 3

Bank voles, small rodents and insectivores

Question 4

What are the vectors of TBEV? And which subtypes are spread by these?

Answer 4

Ixodes ricinus (Eurpean) and Ixodus persulcatus (Far East and Siberian)

Question 5

What are transmission routes of TBEV?

Answer 5

Tick bite, and ailimentary route via unpasteurised milk of ruminants (esp goats)

Question 6

What are the clinical symptoms of TBEV?

Answer 6

> 70% asymptomatic
2/3 of patients have biphasic course
ILI - fevers, thrombocytopaenia, leukopenia, and then afebrile and asymptomatic for up to 20 d
Followed by CNS disease - headache, meningitis, meningo-encephalitis, encephalomyelitis, encephaloridiculitis, paralysis

Question 7

What is the fatality rate and sequale for TBEV?

Answer 7

1% fatality (but higher in Far Eastern 5-20%)
Long lasting neuropsychiatric sequlae in 10-20%
There is a rare chronic form of the disease mainly seen in the Siberian subtype

Question 8

At what stage of TBEV real-time PCR in blood useful?

Answer 8

During the first phase, when there is a viraemia of ~7 days

Often not useful in practice as patient’s don’t present until the second phase

Question 9

What diagnositc tests would you use for TBEV CNS disease?

Answer 9

TBEV IgM and IgG in blood (intrathecal Ab can be used but may be falsely negative) - PRNT used for Ab titres

CSF shows PBMs, lymphocytosis and raised protein

Question 10

What are the differential diagnosis for TBEV, and what are specific viral neurological differentials?

Answer 10

Anaplasmosis, borrelia, babeoisis, tularaemia

West Nile, Japanses Encephalitits virus, HSV, Powassan, entero