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Bovine Viral Diarrhoea Eradication Scheme Update

24 July 2013

UK - Bovine viral Diarrhoea, or BvD, is a highly contagious viral disease of cattle which can be easily transmitted through direct contact with infected animals and also indirectly by contact with visitors and machinery from other farms.

Infection with BvD can result in a wide range of clinical signs including reproductive problems and aweakening ofthe immune system leaving cattle more susceptible to other infections, particularly scours and pneumonias in calves.

Agrisearch, in conjunction with the DARD ResearchChallenge Fund, have recently funded a study to identify the proportion of dairy and suckler herds which currently have, or have been recently exposed to infection with the BvD virus. 

Blood samples taken during routine brucellosis herd testing on 589 randomly selected herds across Northern Ireland between April 2011 and June 2012 underwent analysis. The results indicated thattwo thirds ofthe herds tested had at least one animal that had been in recent contact with the virus.

The majority of infections with BvD occur after birth with animals becoming transiently infected (TI) before recovering and becoming virus negative after about three weeks. Transient infections may occur without obvious clinical signs but dependent on the age, sex and immunity of the animal can result in a range of reproductive problems, including abortion.

Transient infections can also result in the occurrence of scour and/or pneumonia that respond poorly to treatment, particularly in calves.

If a cow comes into contact with the BvD virus between 30 and 120 days of pregnancy the unborn calf will become persistently infected (PI) with BvD if it is not aborted. If the calf is born alive it will shed BvD virus at high levels for life and will therefore act as a significant source of infection.

TI animals shed virus at much lower levels and only for a few days.

PI animals may appear healthy at birth but may become stunted and perform poorly as time progresses. PI animals often develop a severe and always fatal wasting condition called mucosal disease (MD).

This usually occurs between 6 and 18 months of age with the majority of PI animals dying before they reach breeding weight or slaughter age due to MD or other infections which the BvD virus leaves them exposed to, particularly scour and pneumonia.

The BvD virus persists in herds through the creation of further PI calves, therefore the identification and removal of PI calves as soon as possible after birth is the key to controlling the spread ofthe virus. vaccination of breeding stock to maintain immunity can offer further protection where susceptible pregnant cattle are exposed to the BvD virus.

A recent study estimated that the BvD eradication programme in RoI would give a cost benefit of 10:1 over the six years of the programme, i.e. a return of €10 euro for every €1 spent.

Animal Health and Welfare NI (AHWNI; www.animalhealthni.com) was established in 2012 as an industry-led, not-for-profit partnershi to address diseases and conditions of cattle which are endemic in Northern Ireland, including BvD, but which are not currently subject to regulation or coordinated programmes of control.

To develop and put in place a BvD programme, AHWNI have convened a cross-industry BvD Implementation Group (BvDIG) which LMC is actively involved in along with representatives of the farming and veterinary organisations,the dairy and beef breed societies, AFBI,CAFRE,DARD.

The programme is based on identifying and culling PI animals from the national herd as soon as possible after birth through the testing of ear punch samples collected during the administration of BvD tags. The identification of a PI animal in a herd will require further testing,focusing on the dam of the PI calf in the first instance,to identify any other PI animals that may be present.

The BvD Eradication Programme has begun with a voluntary phase in 2013 with the proposal by industry to move to a compulsory phase in 2014.

Already farmers have demonstrated their support during the voluntary phase of the programme through ordering tissue tags (accounting for approximately 25 per cent of all tags sold in 2013) and following the programme guidelines. With continued support from the farming industry for the NI BvD Eradication Programme LMC looks forward to BvD being a thing of the past.

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