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| TICK-BORNE ENCEPHALITIS |
Disease
Tick borne encephalitis is cause by TBE virus. It is usually a consequence of exposure to infected ticks, although unpasteurized cow’s, sheep’s and goat’s milk are recognized forms of transmission. The incubation period is 7-14 days for tick borne exposures but only 3-4 days for milk ingestion. The principal reservoirs for TBE virus are small rodents; humans are an accidental host.
Occurrence
Tick borne encephalitis is caused by TBE virus. It is usually a consequence of exposure to infected ticks, although unpasteurized cow’s, sheep’s and goat’s milk are recognized forms of transmission. The incubation period is 7-14 days for tick borne exposures but only 3-4 days for milk ingestion. The principal reservoirs for TBE virus are small rodents; humans are an accidental host.
Risk for travellers
Travellers who walk and camp in infested areas during the tick season (usually spring to early autumn) are at risk and should be vaccinated. Some degree of protection is afforded by clothing that covers as much skin as possible and by applying insect repellent.
Vaccine
Tick-borne encephalitis vaccine is licensed for immunization of those in high-risk areas. Those working, walking or camping in warm forested areas of Central and Eastern Europe and Scandinavia, particularly from April to October when ticks are most prevalent, are at greatest risk of tick-borne encephalitis. Ideally, immunization should be completed at least one month before travel.
Two vaccines are available in Europe, in adult and paediatric formulations. These are inactivated whole-cell vaccines containing a suspension of purified tick-borne encephalitis virus grown on chick embryo cells and inactivated with formaldehyde. Both provide safe and reliable protection. Immunity is induced against all variants of the tick-borne encephalitis virus including the European and Far Eastern subtypes. Two doses of 0.5 ml should be given i.m. 4–12 weeks apart. A third dose is given 9–12 months after the second dose and confers immunity for 3 years. Booster doses are required to maintain immunity and should be given every 3 years if the risk continues. Outside endemic countries, the vaccines are not indicated. |
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