Novartis Animal Health has announced the results of a survey of dairy and beef farmers which found that 39% of those who found Bovine Viral Diarrhoea (BVD) present in their herd did not then go on to test for persistently infected (PI) animals.

Any calf born from a BVD persistently-infected cow will be born Persistently Infected with the virus and cannot be cured. As a result, future vaccination of this animal against the virus is rendered ineffective and the affected animal will be a source of the virus, spreading infection within the herd.

With young cattle being the source of PI's and reservoirs of infection within a herd, failure to test, identify and then deal with PI livestock represents the most significant problem facing the industry when trying to eradicate BVD.

Professor Joe Brownlie from the Royal Veterinary College and current chairman of the BVD Scientific and Technical Working Group, said: "Of the 61% of farmers that did do follow up tests for PI's once BVD had been detected in their herd, one third found one or more PI's within the stock holding.

"However, one third of farmers who identified having active BVD infection in their herd then failed to go on and carry out individual animal testing; of those that did, nearly half discovered one or more individual PI's within their herd".

"It just shows that the disease can be hidden, and farmers could be in the dangerous position of potentially missing PI animals that are in their herd; PI's that can continue to spread the BVD virus amongst other cattle and pass on their PI status to any calves they produce. It is hugely important to be thorough and consistent in your testing as part of an agreed herd health plan"

The survey also indicated that action needs to be taken to educate farmers about what to do once BVD and, most significantly, PI's are discovered amongst a herd. 

Professor Brownlie said: "There is much evidence from this survey to encourage the industry in how it is tackling this disease, however there is still a great need for clear direction.  The survey indicated that 20% of farmers wrongly believe that PI animal's will eventually become non-infective and that 25 % believe that calves born of PI cows will not always have PI calves themselves.

"All of these perceptions are incorrect and can lead to reservoirs of the disease being allowed to remain not only within individual herds, but geographical regions as well; seriously hindering the eradication of the virus in England and Wales".

With nearly half of farmers saying that they talked to vets - their main source of information about BVD - only once or less a year, Professor Brownlie said it is unsurprising that many farmers did not show a greater understanding of BVD beyond biological side effects present in the infected cattle: "About 50% of farmers surveyed were unsure as to what types of tests need to be carried out to detect the infection in their livestock and 32% of respondents were unaware that correct vaccination of livestock against BVD can protect both the cow and unborn calf".

Novartis says that while BVD is still regarded by farmers as one of the top bovine diseases, other health issues such as mastitis and tuberculosis are given much greater attention. This lack of focus on BVD is exacerbated by the lack of sound information of the financial implications of the infection on their herd. 

Professor Brownlie said: "The side effects of BVD appear to be overlooked in financial terms, but the infection can severely hinder a herd's financial productivity due to poor health, reduced milk yield and loss of reproductive efficiency.  

Caroline Dawson from Novartis Animal Health said:"Perhaps by aiding understanding of the financial cost of the virus, we can encourage farmers to take more proactive steps to combat BVD. As such, I am pleased to announce that that the FAB panel has initiated a follow on project to carry out detailed research with regards to the financial impact of BVD on farms and is due to report findings in the new year". 

(Photograph shows, left to right, James Russell MRCVS (McMurtry & Harding), Caroline Dawson (Novartis Animal Health), Tony Brooks (Brighthams Farm), Professor Joe Brownlie(RCVS)

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