A new petri dish-based technique has provided a breakthrough in the science being used to investigate the cause of Bleeding Calf Syndrome.
Speaking today (January 16th 2013) at Quality Meat Scotland’s Research and Development Conference in Dundee Dr Kim Willoughby, Head of Viral Surveillance Unit at Moredun, said the new bone marrow biopsy technique should accelerate progress to establish the cause of the complex disease.
Bleeding Calf Syndrome, also known as bovine neonatal pancytopenia (BNP), is caused by antibodies in the colostrum which attack the bone marrow cells of the calf after suckling.
The dramatic clinical signs, occurring almost exclusively in calves of less than 21 days old, are widespread internal and/or external bleeding. Common sites of bleeding are from the nose, from small wounds such as ear tagging or injection sites, and into the intestine causing blood in the faeces.
Not all affected calves show signs of external bleeding - some may be found dead. In the UK, researchers from Moredun, SAC, VLA and the Royal (Dick) School of Veterinary Studies have been working together to try to establish the reason for the sudden emergence of the disease and its cause.
The breakthrough technology described by Dr Willoughby was funded by QMS as part of a wider project funded by the Moredun Institute Fund, with a student funded by the EU’s Leonardo Scholarship Programme.
Bleeding Calf Syndrome is known to be associated with the use of a Bovine Viral Diarrhoea Virus (BVDV) vaccine which has been withdrawn from the marketplace. Vaccinated dams produce antibodies in the mother which attack the bone marrow of the calf after drinking colostrum.
Despite the vaccine being withdrawn cases of Bleeding Calf Syndrome continue to be found in some calves born to dams which have been historically vaccinated.
“Interestingly, only a very small proportion of vaccinated animals bear calves which suffer from BNP. The reasons for this are unknown but may be due to cow/calf interactions while the cow is pregnant and this could impact on future vaccine development or usage,” said Dr Willoughby.
The new petri dish technique allows bone marrow cells sourced from live calves to be grown in petri dishes. This will, said Dr Willoughby, allow far larger numbers of animals to be studied, compared with techniques using tissue from dead animals, saving time and cost.
“Using this petri dish method we have shown that, even when the bone marrow looks normal under the microscope, the cells are damaged and do not work properly,” she said.
Bleeding Calf Syndrome remains a problem in commercial and pedigree beef cattle herds.
“While it is likely that the disease will naturally fade out over time as the number of vaccinated dams producing calves continues to fall, the results of research into the emergence of the disease could be vital in preventing a recurrence of a similar problem.
“We are looking at a situation where 100,000s of doses of vaccine were used and yet only a comparatively small number of calves were affected.
“One possibility is that it is not the vaccine itself which directly causes the problem but the individual reaction to the vaccine of specific animals,” observed Dr Willoughby.
“It is important to understand what triggered the problem. The fact is a very good BVDV vaccine was withdrawn as a result and my hope is that by understanding what is at the root of this problem we will be better able to design vaccines in the future.”