Elimination of bovine viral diarrhoea virus in New Zealand: a review of research progress and future directions.

The major impacts of bovine viral diarrhoea (BVD) on cattle health and production have prompted many countries to embark on national elimination programmes. These programmes typically involve identifying and removing persistently infected (PI) cattle in infected herds and implementing biosecurity measures, such as pre- or post-movement testing. In order to design a systematic national control programme to eliminate BVD in New Zealand, which achieves the greatest benefits to the industries at the lowest cost to individual farmers, an accurate understanding is necessary of the epidemiology, economics and social motivation for BVD control in New Zealand. In this article we briefly review the pathogenesis of BVD, transmission and diagnosis of BVD virus infection, and effectiveness of vaccination. We summarise the current state of knowledge of the prevalence, risk factors for transmission, and financial impacts of BVD in New Zealand. We describe control programmes in Europe and then discuss the challenges that must be addressed to design a cost-effective national control programme to eliminate BVD in New Zealand.

Assessment of the duration of the pain response associated with lameness in dairy cows, and the influence of treatment.

AIM: To assess the welfare impact of lameness on dairy cattle in New Zealand by measuring the duration of allodynia (decreased nociceptive threshold) and increased locomotion score, and to evaluate the influence of treatment on that duration. METHODS: After lame cows were treated using corrective paring by a veterinarian, they were allocated to one of six treatment groups. If the veterinarian determined that additional elevation of the lesion was not required the cow was randomly allocated to receive one of four treatments, viz 2 mg/kg tolfenamic acid, a plastic shoe to elevate the lesion, both treatments, or no further treatment. Cows that required additional elevation were treated using a plastic shoe and then randomly allocated to two separate treatment groups, either 2 mg/kg tolfenamic acid or no further treatment. Assessments of locomotion score (based on posture and gait) and mechanical nociceptive threshold (using a pneumatically actuated blunt pin) were made prior to treatment, and 3, 8, 28 and 100 days later. RESULTS: Data were collected from 149 lame cows from nine dairy farms. There were significant improvements in mean locomotion score and nociceptive threshold in all treatment groups. At all time-points after treatment, locomotion score and nociceptive threshold were significantly improved when compared with the previous time-point. Thus, in these cows, the deleterious effects of lameness persisted for longer than 28 days, despite treatment, as the mean locomotion scores and nociceptive threshold on Day 100 were better than those on Day 28. No significant long-term benefit of using tolfenamic acid at the time of treatment was observed on either locomotion score or nociceptive threshold, nor was there any benefit in using a plastic shoe in cases where it had been determined that such treatment was not necessary. CONCLUSIONS: This study demonstrated that the welfare impact of lameness on dairy cattle in New Zealand is of long duration even when treated effectively. In contrast to previous studies, no significant long-term benefit of using non-steroidal anti-inflammatory drugs (NSAID) at the time of treatment was observed, probably because unlike those previous studies the nociceptive threshold improved in the cattle which did not receive an NSAID, perhaps because treated cattle were kept on pasture rather than housed. CLINICAL RELEVANCE: The long duration of increased allodynia after treatment demonstrates that prevention of lameness rather than therapeutic treatment is the key to reducing its impact on the welfare of dairy cows.