Efficacy of bivalent fimbrial vaccines to control and eliminate intermediate forms of footrot in sheep.

OBJECTIVE: The aim of this study was to determine the efficacy of serogroup-specific bivalent fimbrial vaccines in the control and elimination of relatively mild (intermediate) forms of footrot in sheep flocks in NSW, there being some evidence that such forms are difficult to control. METHODS: Four flocks of sheep with history of footrot of intermediate virulence were selected based on clinical and bacteriological diagnoses. Dichelobacter nodosus serogroups included in bivalent vaccines at each farm were based on on-farm serogroup-prevalence data. Two doses of bivalent vaccine were administered with a 4-week interval between doses. Repeated post-vaccination inspections of all feet of between 100 and 119 animals per mob were conducted and foot swabs were collected for bacteriological testing. Blood samples were collected from 10 to 24 individually identified animals per flock at each inspection to check for agglutinating antibody responses. RESULTS: In the majority of animals, antibody levels for serogroups included in each vaccine were above the level believed to be required for protective immunity. Footrot disappeared on farm 1 prior to vaccination, but did not reappear postvaccination. Footrot was controlled but not eliminated on farms 2, 3, and 4, where the prevalence and severity of the disease and number of serogroups present were reduced. CONCLUSION: Serogroup-specific bivalent vaccines can be effective at controlling footrot caused by intermediate strains of D. nodosus.

Relationship of glomerular phagocytic cells to immune complexes and DNA autoantibodies in NZB/W mice.

Systematic study of groups of NZB/W mice aged from 1-8 mth showed progressive development of antibodies to ssDNA and dsDNA, accompanied at 5 mth by the appearance of serum immune complexes as detected by Clq liquid phase binding and immune deposits in glomeruli. Cellular outgrowths in cultures of isolated glomeruli showed increased numbers of phagocytic cells as well as epithelial and mesangial cells, reaching a maximum in mice aged 7 mth. These numbers exceeded those found in control CBA mice and, while consistent with the hypothesis that phagocytic cells are involved in the processing of immune complexes lodged in the glomeruli, also reflected the hypercellularity of the glomerular lesions.