SRUC: Lymph Node Aplasia In Scottish Blackface Lambs

Update from SRUC: Lymph Node Aplasia In Scottish Blackface Lambs

This condition has now been diagnosed in lambs from ten Scottish blackface flocks.  Affected lambs appear healthy until they develop severe orf between the ages of two and six months.  They do not respond to treatment and if they are not euthanased will continue to lose weight and die.

Postmortem examinations have shown that these lambs have been born without any lymph nodes.  Lymph nodes are a vital part of the immune system explaining why these lambs are unable to cope with, and recover from, orf.  Some are likely to die from other, less visible infections.  The expectation is that many of these lambs will die before they are six months-of-age.  However, we have diagnosed the condition in a 14-month-old ewe hogg raising the possibility that some could survive to breeding age.

The only plausible explanation for a failure of the lymph nodes to develop is an inherited condition.  Genetic typing of samples from a number of affected lambs, dams and sires has been carried out in collaboration with researchers at the Roslin Institute in Edinburgh.  Unfortunately, it has not yet been possible to identify the gene or genes responsible.

We would like to thank flock owners who have already submitted lambs for investigation and allowed follow-up blood samples to be collected.  The Blackface Sheep Breeders’ Association are writing to their members to raise awareness of the condition and encourage flock owners who think they have seen cases either this year, or in the past, to get in touch with their vet/SRUC Veterinary Services.  Any information provided will be treated with the strictest confidence.  Further samples from affected lambs plus their dams and their sires are required to help find the cause.  Only then will there be the possibility of developing a screening test for tups in the future.

Heather Stevenson, SRUC Veterinary Services

Email: heather.stevenson@sruc.ac.uk