The First Case of Bluetongue

I fear we will remember September 22^nd 2007 as the day when the world changed. When I wrote about Bluetongue virus last month I had no idea that it would arrive here so quickly when we were still battling with the after affects of the Foot and Mouth outbreak. All of the things we talked about in the last news letter are relevant to the occurrence of the disease in Suffolk. In the week preceding the diagnosis our weather was coming from the West. The Highland Cow that started it all had been under investigation for five days for Foot and mouth Disease before Bluetongue was suspected and diagnosed. Four days later a cow fifty miles away was found to be infected. It would seem to me that infection is widespread and difficult to detect until full investigations are undertaken. It is not clear when the infection first arrived in the country.

How it Spreads

Different ruminants vary as to their susceptibility to the Bluetongue Virus. It is reported that some breeds of sheep can suffer mortalities of seventy percent within two weeks of the infection starting. Others have found that cattle and wild deer can carry the infection and show no apparent symptoms. It is difficult to understand why the affected animals have been slaughtered, unless their symptoms were so severe to cause suffering. The virus can only be transmitted by a biting midge. Theoretically contaminated needles can pass the infection on, but this has never been proved. Our experience with Horses and sweet itch show that midges keep out of enclosed buildings, if the carrier animals were housed they would not be a risk to others. The chances are that there are many apparently healthy ruminants in East Anglia that are quietly carrying the virus and it would not be possible to slaughter all of them.

Can we stop it?

Intervet claim that Butox Swish does kill midges on cattle. The problem is it only works after they have bitten so it will not stop the infection spreading to cattle but it will reduce the midge population and stop infected cattle passing the virus on if it is applied to them. It is thought that cattle can carry the virus for up to fifty days and that sheep are infectious for up to twenty days. These figures should not relied upon totally as it is known that the infection can remain dormant in some animals for longer periods of time.

Restricted Area

There is no advice that I can give you to protect your stock against this new infection. As things stand Norfolk, Suffolk, Essex, Bedford, Leicestershire, Lincolnshire, Northants and Cambridgeshire are under specific Bluetongue restrictions. Essentially this means that no ruminants can move out of these Counties. It will be devastating for keepers of pedigree cattle and sheep. Disinfectant buckets will not help us in the fight against Bluetongue. We cannot rely on a hard winter to check the progress of the infection. The only thing that might help is the Merial Laboratory at Pirbright where they are working flat out to develop a vaccine against this serotype of the disease. They have promised that this will be available in March next year.

That other Disease

As well as this Foot and Mouth rumbles on eight farms affected so far. This time there have been more farms outside of Surrey placed under temporary restriction, thank fully so far all of these have been withdrawn after 48 hrs. As I understand it at the moment you are able to move stock both within your sole occupancy license or between holdings using the General license, no veterinary inspection is required. Pigs can only move between farms after a veterinary inspection. At the moment these movements trigger a twenty day standstill for any future movements except direct to slaughter. From Thursday the 4^th October Green Markets will start trading again under heightened bio security measures.  This outbreak is far from under control, if there is anything that you need to move it might be better to do it now because there is a constant danger that stricter controls will be put in place again.

Diagnosing BVD

Recently there have been significant developments in laboratory tests that can be done from animal samples and there are many more things that we can do to diagnose disease. One of the more exciting ones is that it is now possible to detect the BVD virus from a bulk milk sample. It is reported that the test can detect just one cow that is excreting the virus in a herd of up to three hundred cows. Agitated samples from one milking are required and the number of cows milked is needed to estimate the significance of the amount of virus found.

Detecting Carrier Animals

BVD persists in a herd because of cows that carry the infection and pass it on to others. In the past the only way to detect such cows was to blood sample the whole herd. If you get a positive result after the milk test you will still need to resort to blood tests to detect the individual infected animals. It is now possible to pool batches of ten blood samples to save some of the costs. Once it has been determined which batch the culprit is from we can start to look for the individual cow. This sounds complicated but it will mean that it will not be so expensive to detect BVD in dairy herds from now onwards.

Look out for Liver Fluke

It is a long time now since there was an official fluke forecast the task has been taken over by a drug company that produces a fluke drench so you have to interpret their assessment with a little bit of caution. This year I think they are right, the wet weather in the summer came at the right time for the snails that are involved in the complicated life cycle that fluke have. Already there have been reports of acute facioliasis in sheep from Penrith, Winchester and Carmarthen. We are not in an area where there is a big fluke problem but if you ever get fluke you are likely to get it this winter. Cattle can carry fluke for years undetected sometimes as they do not pick up enough of the parasite to affect their condition but they keep contaminating pastures to maintain the like cycle. On most farms January is the best month to drench sheep and cattle for fluke as they will continue to pick up the larvae until well into the winter and late infections may be missed by early dosing.

Lungworm

It has become apparent in recent weeks that many of you have grazing cattle that are coughing, and I have heard reports of dairy heifers dying because of lungworm infections. There is a tendency now to delay the last worming of the season until close to when your stock is housed. That might not work this year as the immune system of the cattle can become overwhelmed if there are too many larvae on pastures. These worms do extensive damage to the lungs prompt action is required to rectify the situation.

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