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====Control====
====Control====
*Recovered animals show immunity ONLY to the subtype of first exposure, and even this is relatively short-lived
*Re-exposure to the original serotype after immunity as waned will still result in virus excretion, even without clinical symptoms
*Infection by a second serotype will result in clinical disease
*For these reasons, '''vaccination is not practiced''' in the UK
**Further, vaccination would mean a loss of meat export markets