Caseous lymphadenitis: Present and near forgotten from persistent vaccination?

Abstract

Ovine caseous lymphadenitis (CLA) is a serious disease of the global sheep industry, mainly causing losses from abattoir condemnations and in some countries, compromised productivity. However in Australia, CLA is now of minimal concern on-farm with cases reported rarely, although the disease remains an important food quality issue for abattoirs. There is evidence from longitudinal abattoir surveillance that CLA prevalence has been declining, from estimates of 26% in 1995–5.2% in 2009. Change management factors relevant to reduced prevalence and producer concerns for CLA in Australia were examined, including drivers and motivation for change, resistance to change, knowledge management, farming systems dimensions and leadership. Although extension programs addressing disease risk factors, such associations of CLA with dipping for external parasite control and frequency of close confinement, may be of relevance to improved disease risk management by producers, improved CLA control on many Australian sheep farms is considered largely attributable to the introduction of vaccination programs for CLA in 1983, with inclusion of CLA antigen within clostridial vaccines (‘6 in 1′ vaccine). This innovation enabled routine annual CLA vaccination to occur in an increasing proportion of the national flock, despite several surveys that have shown that producer knowledge of CLA is low. However, promoting the persistent use of ‘combination' vaccination to continue suppression of CLA infection and improved biosecurity to reduce re-introduction of disease, plus targeting properties that are not using vaccination, remains a challenge for animal health authorities. As CLA in Australia is now primarily an issue for the sheep meat processing sector, efforts to improve feedback to producers suffering carcass condemnations at slaughter should be encouraged. Persistent vaccination for CLA improves the health and welfare of sheep and this strategy deserve wider recognition in all sheep and goat production countries where vaccine usage is sporadic.