The Bovine Viral Diarrhoea (BVD) Eradication Scheme phase 4: guidance for vets

Part 9 Current Bvd Situation

What is the prevalence of BVD?

Original SAC surveys prior to the eradication scheme estimated BVD exposure (herds testing not negative) at 40%. Through increased awareness and action on the disease, the voluntary testing of around 50% of herds in Scotland revealed that just under 30% of herds had been exposed. The current level of BVD exposure in Scottish herds is around 16% as indicated by not negative test results. This shows that the steps being taken so far by the industry and by vets is producing a substantial reduction in BVD disease prevalence in Scotland. Over 2,000 persistently infected animals have already been identified and the vast majority of these are now dead.

Differences in disease prevalence, beef and dairy

Since the introduction of mandatory screening the percentage of beef herds testing not negative for BVD has reduced to 12%, and there has been a recent reduction in the exposure levels in in dairy herds, which are now at 39%, having stayed static at around 50% testing not negative for the past few years. The bulk milk tank will indicate infection throughout the history of a herd and may indicate a historic rather than current infection. The removal of the bulk milk tank tests should give a more accurate picture of the level of exposure in dairy herds.

Differences in BVD exposure levels by county

You can see by the above map from 2014 that there are differences in the levels of exposure to BVD by county. The darker the area the higher the incidence of BVD exposure in that county. For those who have a not negative status in a low BVD area, hunting and removing PIs will make a big difference to the county status. For those who have a negative result in counties with a higher prevalence, biosecurity is of great importance.

Bvd Myth Buster

1. Got BVD? Don't worry, you can just vaccinate.
FALSE - Vaccination does not deal with PI animals. They continue to spread infection potentially creating yet more PIs in spite of herd vaccination.

2. You should keep a PI animal on the farm so that your animals are not naive, i.e. the idea of PI parties.
FALSE - PI animals are highly infectious and should be culled as soon as they are identified. They will cause huge problems on your farm. Vaccination is the only effective way of protecting naive animals that may come into contact with BVD.

3. The government is making vaccination compulsory/the government is banning vaccination.
FALSE - Vaccination will continue to be an important part of controlling BVD for many herds, but it is a decision to be taken between keepers and vets.

4. You can't get rid of BVD, because of transient infection.
FALSE - The evidence is overwhelming that removing the PI animals will stop the disease from circulating. Transiently infected animals are much less infectious than PIs, and only for a short period of time, if they are infectious at all.

5. There's no point in getting rid of BVD, because my herd will be re-infected by sheep/deer.
FALSE- Sheep can carry BVD and can re-infect your herd, but only if they have been in contact with cattle with BVD in the first place. Removing the source of infection - the PI cattle - will reduce BVD among sheep. Also, transmission from sheep to cattle is very weak, so only a small number will be unlucky enough to get re-infected this way. To be sure though, you should keep breeding cattle away from sheep.
Deer can carry BVD, but we've no evidence to think this is a significant problem, and again, removing PIs will remove a major source of infection for deer.

6. It's impossible to eradicate BVD from my herd - I've been trying for years.
FALSE- The vast majority who have followed a CHeCS scheme have got rid of BVD within two years. If you test to find your PIs, slaughter them, buy-in only BVD-free cattle or isolate and test them, test your calves for two years, and exercise good biosecurity, you should get rid of a BVD infection in around
two years. All the studies show that the benefit to your profits will far outweigh the cost of getting rid of BVD.

7. I've got a PI animal, but it looks alright so I don't need to slaughter it, I'll just finish it.
FALSE- Very few PI animals ever reach a good slaughter weight. While it's on your farm it is a significant disease risk to the rest of your herd. It's always better to send it for slaughter immediately.