Dutch vet warns: learn from our experience - Veterinary Practice
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Dutch vet warns: learn from our experience

Livestock producers in the UK should not underestimate the continuing threat posed by the bluetongue virus or its potentially devastating impact on their businesses.

Livestock producers in the UK should not underestimate the continuing threat posed by the bluetongue virus or its potentially devastating impact on their businesses.

They must also understand that if, for whatever reason, they choose not to vaccinate they will expose themselves, and other farms in their area, to very real and substantial risks, warns a leading Dutch veterinarian who has dealt with numerous cases of bluetongue in cattle, sheep and dairy goats during the last three years.

“The threat from bluetongue is so great that I advise all my clients to vaccinate their livestock as a matter of routine. The risk from vaccination is extremely small, whereas by not protecting their herd producers are simply taking an enormous gamble with their own and everyone else’s livelihoods,” states Niels Groot Nibbelink, who specialises in ruminant livestock and is a partner in the Someren Veterinary Centre near Eindhoven.

One of the country’s leading veterinary practices, it employs 22 veterinarians and in 2008 vaccinated 25,000 animals against bluetongue. In addition to his veterinary work, Niels also writes articles about the disease for the Dutch agricultural press, lectures to farmers and students and owns a herd of naturally calving, double-muscled Belgian Blue beef cattle together with a small flock of Texel sheep.

Soon after bluetongue was confirmed in The Netherlands during August 2006, Niels encountered his first case in a client’s sheep flock. Suspecting that it might be foot-andmouth he sought a second opinion from the Dutch Veterinary Authority at Deventer. Blood samples from the farm tested positive for bluetongue and just a few days later the disease was confirmed in another client’s cattle. With most farmers knowing little about the disease at that time, Niels collated information and published it in the veterinary centre’s newsletter and on its website.

Only 20 or 30 farms in The Netherlands were affected by bluetongue during 2006 and the onset of winter temporarily halted its progress, but the very mild weather provided a favourable environment for the midges which spread the disease and it came back with a vengeance in 2007.

Ideal conditions

Interestingly, many farmers felt that measures designed to encourage them to return pastures back to nature and leave ponds unmanaged in the name of conservation had provided ideal conditions to harbour midges and exacerbated the problem. Although many used pour-on products to try to control midges, by July 2007 the country faced a bluetongue epidemic.

“In 2007 we saw a huge increase in the number of sick animals and this was reflected in the amount of pain-control medication which we prescribed, which was four times that supplied the previous year. We encountered a lot of foot problems such as claw lesions which resulted in lameness, while the reproductive performance of both male and female livestock was greatly reduced. The impact on conception rates varied between herds, but in some of the 120 herds which we advise the average number of days between calving increased from an average of 390 days to 450 days.

“A lot of cattle were very late getting pregnant that year. Although they were inseminated at 16 months they aborted three or four months into pregnancy and had to be returned to pasture with the bull, so the long-term effects on herd performance became very noticeable in 2008 and were often severe. In one 90-cow dairy herd, for example, over 25% aborted, while in others milk yields dropped by 10 to 40%.

“While some farms were badly affected, others did not seem to suffer to the same extent and no farm had the same symptoms, the intensity also being different on each unit. In a 100-cow herd you might see half a dozen with a nasal discharge, others that looked as though they were walking on eggshells due to sores on their feet, while some had lesions on their teats.

“My view is that the standard of farm management played a very important role in the severity of the symptoms experienced, while some of the difference could have been down to the underlying presence of BVD mucosal disease which increased the intensity of bluetongue. In The Netherlands we have a lot of herds that are certified free from BVD and we were therefore able to exclude that as a contributory factor on those units.

Careful management

“There was a lot of difference over how veterinarians and farmers reacted to the disease during 2007 and its effects on their businesses. On my own farm all the sheep were affected, but by careful management such as providing them with plenty of water and soft food to encourage them to drink and eat, I was able to minimise the effects.

“The overall impact of bluetongue was so severe during 2007 that almost everyone who experienced it, or knew someone who had, didn’t think twice about whether to vaccinate the following year when the opportunity was there to do so. They just did it! However, despite all the compelling evidence, many farmers in the north of Holland still didn’t vaccinate, for various reasons. “Some refused to do so because they didn’t agree with vaccination due to their religious beliefs, others mistakenly thought that the disease would not affect them, while others had listened to the gossip at markets and thought that vaccination produced adverse side effects, including abortions.

“We started vaccinating immediately the Government authorised it in May 2008 because many of our clients are breeders and didn’t want to take risks with the health of their very valuable stock. Although most animals were already out at pasture by then, we still treated 25,000 sheep and cattle.

“I had a few hard words with two or three of the farmers who refused to vaccinate, even though the full cost was being met by government and they were in a high-risk area. Given the risk to others it was a very selfish attitude.

“Farmers should vaccinate as a matter of routine, especially sheep which suffer from higher levels of mortality, often more than 30% compared with an average of 2% in cattle. A lot of sheep died in last year’s outbreak and large number of farmers went out of business. Consequently, the majority of those who remain have no hesitation in vaccinating again this year even though they will have to pay the full cost themselves.

Brian Rice, a veterinary adviser with Merial Animal Health, comments: “The experiences of vets and farmers in The Netherlands provide a valuable lesson for producers and vets in the UK. Vaccination is an extremely costeffective insurance against the considerable risks from bluetongue, which can be devastating in terms of its adverse economic impact on farm businesses.

“The high uptake of vaccine in the south-east of England and East Anglia during 2008 appears to have been a major factor in helping to prevent the spread of bluetongue in the UK. However, it is important for livestock farmers to understand that the threat from the disease remains, primarily being spread via imported stock and midges being blown over from the continent.

“They must therefore implement measures to protect their businesses and understand that if they wait until neighbouring herds show signs of the disease before vaccinating it will be too late to protect their own livestock. If they have not been vaccinated before, cattle require two doses of vaccine and it takes three weeks after the final dose to build up full immunity. Early preventive measures are therefore essential.”

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