Study of intermediate footrot in New South Wales (NSW) Australia

Ovine footrot is a contagious disease of sheep caused by Dichelobacter nodosus which results in production losses and compromises the welfare of animals. The severity of disease which develops is on a spectrum, with benign, intermediate and virulent forms of disease described. The pathogenicity of three aprV2-positive D. nodosus field isolates were tested in a pen trial. Foot lesions typically associated with benign or intermediate footrot developed in the animals inoculated with the arV2- positive isolates. The efficacy of a serogroup specific bi-valent vaccine against benign and intermediate footrot was tested in four sheep farms in NSW. The use of the serogroup-specific vaccine can be effective at controlling some intermediate strains of D. nodosus. The antibody concentrations for the serogroups included in the vaccine at each farm were generally above concentrations required for protective immunity. The utility of pooled sample testing was examined using 572-foot swabs samples collected from six sheep farms in Tasmania and one farm in NSW. The test sensitivity (Se) and specificity (Sp) of the three multiplex PCR assays differed between sample types, individual serogroups and each of the three multiplex PCR assays. The pooling of five DNA samples may improve the cost effectiveness of diagnostic testing. A questionnaire survey was developed and completed by 43 sheep farmers in NSW. Risk factors associated with footrot and other hoof diseases were identified and it was determined sheep farmers in NSW consider benign and intermediate footrot an important disease which negatively affects the health and welfare of affected animals. The association between the aprV2 gene and virulence has not been established in Australian strains of D. nodosus. A method was developed to examine gene expression levels and when incubated for 5 days, the level of gene expression of isolates classified as virulent was higher than isolates classified as benign