Border disease virus causes reproductive failure and produces persistently infected "hairy shaker" lambs. Prevention through biosecurity and vaccination protects flock welfare.
Border disease causes welfare harm at multiple stages: ewes experience pregnancy loss (abortions, mummified fetuses) with associated distress; PI lambs are born with neurological deficits causing tremors and poor coordination that persist throughout their short lives; non-PI infected lambs may have developmental delays and reduced survival. The suffering of PI lambs is ongoing from birth — they rarely thrive, fail to grow well, and typically die young from secondary infections. Prompt identification and humane euthanasia of PI lambs reduces individual suffering and prevents further viral spread.