Investigation of the risks of entry and spread of BVD in herds participating in a regional BVD control programme in the South West

Abstract

Bovine Viral Diarrhoea (BVD) is estimated to cost the UK cattle industry £40 million annually, the third most costly disease facing the agricultural industry. BVD produces a range of symptoms in cattle including scouring, pneumonia, poor fertility, reduced growth rates and lowered milk yields. The most common route of transmission is through persistently infected (PI) animals shedding the virus to other cattle. PI animals can only develop pre-partum when the BVD virus crosses the placenta from the dam to the foetus. If infection occurs during the first 110 to 150 days of gestation, the foetus is immune-incompetent and the lymphocytes are unable to identify foreign bodies, the virus becomes accepted as part of the foetus and is unable to produce antibodies against it; if born alive, the calf will continually shed the virus throughout its life. Animals infected post birth will become acutely infected and shed the virus for two to three weeks before producing antibodies and long-term immunity against the virus (Larska et al, 2013; Booth and Brownlie, 2011; Walz et al., 2010; Smirnova et al., 2008; Brock, 2003; Fray et al., 2000). BVD can be controlled and eradicated, as has been shown in a number of European countries. Currently there are no measures in place nationally in the UK to control this disease; however, a regional control programme was implemented in the South West between 2010 and 2013. This study aimed to establish the level of risk or entry and spread of BVD on farms participating in this programme and determine any common risk areas on these farms. Herds participating in this regional control programme were categorised as red, amber or green for the level of risk of BVD entry and for BVD spread following the completion of a risk assessment questionnaire. Principal Component Analysis (PCA) was used to identify common risk areas for BVD entry and spread within both dairy and beef herds. These risk areas were then used to provide summarised advice suitable for farmers to improve their level of risk management on their farm for both BVD entry and spread and control BVD on their farm.