VACCINE FOR ORF AND MORE?
VACCINE FOR ORF AND MORE?
THE virus which causes orf in sheep may be used in future to create a vaccine which protects against not only that disease, but also stomach and gut worms, according to Peter Nettleton from the Moredun Research Institute, Edinburgh.
"We think the parapoxvirus which causes orf could be used to carry vaccines against worms and other diseases, so that a single injection could give wide protection to sheep," he says.
But the downside is that a new vaccine for orf is five or even 10 years away from commercial production.
"There is a vaccine, of which 2.5m doses are sold each year in the UK. But it is a live vaccine and has been made the same way since 1920. It is awkward to use, requiring the inside leg to be scratched, it spreads uncontrollably, and produces only a short lived, six-month immunity. A new vaccine is urgently required," says Dr Nettleton.
Part of the concern is that the virus is skin based and does not become systemic, making production of a long-life vaccine more difficult. New research is based on finding out how the virus manages to evade the sheeps immune system. It is also looking at the fine detail of the virus to discover which parts could best be exploited for a future vaccine.
Dr Nettleton explains that collaborative work is being done in New Zealand, and a Saudi Arabian vet had compared the sheep orf virus with similar ones attacking cattle, seals and red squirrels.
"It seems that the grey squirrel is immune. That may be part of the reason why its population is increasing while that of the red squirrel is declining," he says.
Orf causes considerable economic loss and welfare concerns in lambs. Usually affecting the mouth, it could cause lambs to literally starve to death because they cannot feed.
Dr Nettleton says that a protracted lambing period indoors with repeated use of lambing pens creates an increased risk of orf spread and he advises thorough cleaning and disinfecting of pens after each use.
Thistles and trough feeding are among the factors which predispose animals to invasion by the virus which can survive for years outside the sheep, and had lived for 26 years in laboratory conditions, he concludes. *
Scientists at the Moredun Research Institute, Edinburgh, estimate that a new vaccine against orf will be available within the next five to 10 years.
Scientists at the Moredun Research Institute, Edinburgh, estimate that a new vaccine against orf will be available within the next five to 10 years.