“Diginostics” - A novel diagnostic test for digital dermatitis in ruminants

Diginostics shall develop a diagnostic test (DD-test) for rapid detection of cattle and sheep suffering from bovine digital dermatitis (BDD) and contagious ovine digital dermatitis (CODD), respectively. The tests will be implemented in a risk management system. Bovine digital dermatitis (BDD) is a severe disease of the skin of the cattle foot. The shift from tie-stall to free-stall housing of dairy cattle in Norway has increased the occurrence of foot disorders including BDD. This leads to impaired animal welfare and reduced livestock production. The disease is endemic in the dairy cattle population in most parts of the world, despite this, laboratory based diagnostic tools are not yet available. Great variation in clinical symptoms makes clinical diagnosis challenging. Contagious ovine digital dermatitis (CODD) is a severe disease of the sheep feet, microbiologically related to BDD. It is endemic in the UK and was recently diagnosed in Sweden. CODD has never been observed in Norwegian sheep and hence it is of great importance to maintain this situation. Bacteria belonging to the genus Treponema are the dominant pathogens in the development of both BDD and CODD. ?Diginostics? will identify Treponema variants associated with BDD in Norway and compare Treponema variants present in Norwegian sheep to those present in British sheep diagnosed with CODD. The DD-test will be based on a polymerase chain reaction (PCR) targeting common gene sequences in the disease associated variants. To meet the challenge with the increase of BDD in Norway, a risk management system for safe trade of cattle will be developed in parallel to the development of the diagnostic test. The risk management part will consist of a combination of data from the DD-test, risk assessments and clinical registration by claw trimmers. A national guideline will be developed which include descriptions of economic measures to encourage the will to register and share data for safe trade in livestock. Biopsies from healthy cattle and sheep feet have been collected. Biopsies from BDD- and CODD-lesions are already collected in the research project ?Digital dermatitis in Norwegian dairy cattle ? a contagious disease threatening the animal welfare? and by the University of Liverpool, respectively. The application in FOTS for collection of biopsies from sheep at Norwegian abattoirs has now been accepted. Biopsies from abattoirs have been collected the current year; however, the collection will continue in 2022. The samples from healthy feet will be compared with samples from diseased feet, to identify Treponema-variants associated with BDD and CODD. DNA-extraction from biopsies as well as 16S sequencing (microbiome studies) have been performed. Furthermore, a work-flow scheme for analyzing sequencing results has been built. Finding genes suitable for the development of a diagnostic test demands mapping of the whole bacterial DNA. To get access to DNA the bacteria must be cultivated. This is a challenging and time-consuming process that is well underway in the project. Swabs, scrapings and hair samples have been collected for cultivation and subsequent validation. A PCR ID has been established for selected Treponemas to ease cultivation procedures on samples from cattle, as well as biopsies from sheep. DNA has been extracted from isolates for WGS. Furthermore, an overview of published WGS isolates has been compiled, which will build the basis for the projects WGS analyses. A ?claw app? has been established (Nordic collaboration) enabling registrations of claw trimming directly in the Norwegian Animal Health Recording System (DHP). A claw-status (red/green) has been developed as a base for secure live-animal trade according to the newly accepted ?national guideline for safer trade in livestock? (BRL). This will demand documentation and to a greater extent include claw health data, to reduce the risk of spreading BDD through trade of animals. As a consequence of the Covid19-pandemic, sequencing and cultivation work at the Veterinary Institute has been halted. Also, farm visits for sampling for cultivation was postponed until June 2021.

“Diginostics” shall develop a diagnostic test (DD-test) for rapid detection of cattle and sheep suffering from bovine digital dermatitis (BDD) and contagious ovine digital dermatitis (CODD), respectively. The tests will be implemented in a risk management system. Bovine digital dermatitis (BDD) is a severe disease of the skin of the cattle foot, was first described in 1974. The disease is endemic in the dairy cattle population in most parts of the world, despite this, laboratory based diagnostic tools are not yet available. CODD is a severe, but relatively new disease, first described in the UK in 1997, it is already endemic in the UK and it was found in Sweden in 2019. CODD has never been observed in Norwegian sheep and hence it is of great importance to maintain this situation. The DD-test will be based on a polymerase chain reaction (PCR) targeting common gene sequences in the bacterial genus, Treponema, associated with BDD and CODD. “Diginostics” will be based on ongoing research on BDD in Norway and Denmark, and on CODD in Sweden and the UK. To meet the challenge with the increase of BDD in Norway, a risk management system for safe trade of cattle will be developed in parallel to the development of the diagnostic test. The risk management part will consist of a combination of data from the DD-test, and risk assessments and clinical registration by claw trimmers. A national guideline will be developed which include descriptions of economic measures (sanctions) to encourage the will to register and share data for safe trade in livestock. “Diginostics” will generate new knowledge about digital dermatitis in cattle and sheep, initiate new measures to control the disease, and reduce the occurrence in Norwegian livestock. It will enhance the effectiveness of the work that the industry is doing and increase the positive effects of planned measures like screening, controlling and potentially future eradication of the BDD in the Norwegian cattle population.