HAIRY SHAKER DISEASE (HSD) CAUSES lambs to be born small, with a hairy fleece and often tremoring or trembling. This can be caused by border disease virus (BDV) or bovine viral diarrhoea virus (BVD).
Sheep catch border disease virus from apparently normal sheep who are persistently infected (PI) with the virus. Sheep can catch BVD from PI cattle who are shedding BVD virus.
Like BVD in cattle, the impact on the lamb will depend on what stage of gestation they were infected. With ongoing exposure in a naïve flock you will see a range of effects from empty ewes at scanning, late ewes (who were infected, lost an early pregnancy, and came back in heat for the last cycle), abortions, lambs born deformed and then dying before docking, lambs born viable but with slower growth rate and higher preweaning losses, and lambs born apparently normal but carrying and shedding the virus all the time. With a single exposure you will get a few but not all of these signs.
Naive means previously unexposed to the virus, so the immune system hasn’t had an opportunity to make antibodies.
That all sounds pretty bad. What is the consequence for a farmer who gets affected by HSD? Imagine you had a pretty good scanning result and were expecting a good docking. Come docking you notice lambs are smaller and your result is 10% less than what you were expecting.
You see some lambs that are falling off when you try to muster them. After a talk with the vet and some blood tests to confirm what is going on, you realise you shouldn’t keep any ewe lambs from this year’s lamb crop – the ones that are showing signs won’t grow well enough to get to mating weight, and those that aren’t showing signs might be PI lambs that will continue to spread it in the flock and affect others.
You continue to see dead lambs between docking and weaning. Then you start to wonder – should you sell these lambs store so that someone else struggles to finish them? How do you make sure someone doesn’t buy the PI ewe hoggets and use them as replacements?
You need to buy in replacements – how will you know you are buying healthy ones? What are the risks to your flock and how can you manage that?
We only sporadically see HSD in the North Island and my experience is that it’s usually from BVD in cattle. In the South Island it is just as commonly from BVD in sheep.
How to prevent this disease affecting you?
To prevent Hairy Shaker from Border Disease virus in sheep, avoid mixing mobs during or just before mating, or in the first half of pregnancy. Most cases occur from naive sheep coming in contact with carriers. If sheep are in contact with the virus when they aren’t pregnant, they will recover and there are no long term detrimental effects.
To prevent Hairy Shaker from BVD in cattle, control BVD in your cattle herd.
About 50% of beef herds still have BVD. If your herd is afflicted with BVD you might see more empty cows, losses in calves, or young cattle with episodes of diarrhoea and weight loss. If you aren’t controlling BVD in your cattle, talk to your vet about what combination of biosecurity, testing and vaccination would work for you. If you don’t do it for your cattle, do it for your lambs.
- Sarah Sutherland is a veterinarian for Veterinary Services Wairarapa.
