Experimental infection of sheep with ovine and bovine Dichelobacter nodosus isolates

AbstractThe aim of this study was, under experimental conditions, to investigate infection of Norwegian White sheep with ovine and bovine isolates of Dichelobacter nodosus of varying virulence. In addition, the efficacy of gamithromycin as a treatment for the experimentally induced infections was examined. The study was performed as a single foot inoculation using a boot. Four groups, each with six lambs, were inoculated with four different challenge strains (Group 1: benign bovine strain; Group 2: virulent bovine strain; Group 3: benign ovine strain; Group 4: virulent ovine strain). The main criterion to determine that infection was transferred was that D. nodosus isolate was obtained by culture. After the trial all lambs were treated with gamithromycin. Clinical symptoms of footrot developed in all groups, and when removing the boots two weeks after challenge, D. nodosus was isolated from 5 of 24 experimental lambs. All lambs tested negative for D. nodosus by PCR within six weeks after treatment with gamithromycin. This study strongly indicates that D. nodosus isolates from both sheep and cattle can be transferred to sheep under experimental conditions. The study also indicates that gamithromycin may be effective against D. nodosus

Development of a Bank of Standardized Blood Samples for the Evaluation of Prion Diagnostic Tests

International audienceAn accurate screening of blood donors would constitute a major improvement for transfusion safety from vCJD infection. Several companies already claim positive results with new ante mortem tests for prion in blood but no standardized samples are available to allow comparative evaluations. In the context of the NeuroPrion BloodDiag project, we have constructed a library of blood fraction samples from sheep for the evaluation of these new tests. Sheep were experimentally infected with scrapie and, in parallel with healthy controls, have been sampled regularly since 2004. Blood was fractionated by the French Transfusion Center of Lille (France) using a protocol similar to the one used for humans. With complete information about the animals (genotype, source of contamination, days post-contamination and presence of clinical signs), this library comprises now more than 8000 aliquots from over 110 different blood samples. Assessment of infectivity of the different blood fractions (plasma, platelets, red cells and buffy-coat) has been performed by inoculation of transgenic mice overexpressing ovine PrP gene (tg338). Successful transmissions were observed with the buffy coat of several animals. Now, two years post-infection, some positive results are also being observed with plasma samples inoculated by intraperitoneal route (a still ongoing study). This bank constitutes a powerful tool for the evaluation of blood tests under development for use as pre-clinical diagnostic screens for TSE infection