A fatal disease of sheep in which there is progressive demyelination of neurons in the brain and spinal cord, caused by a virus.
- ‘It is a voluntary scheme with over 2800 flocks that have been blood tested and are accredited free of Maedi visna.’
- ‘We conclude that sheep sera have a visna virus inhibiting factor and hypothesise that VIF inhibits early spread of visna virus in inoculated sheep and may be involved in initiating the persistent infection.’
1950s: from Old Norse, ‘to wither’.
We take a look at several popular, though confusing, punctuation marks.