Digital dermatitis (DD) is a contagious bovine foot disease characterized by infection of the digital skin with erosions, ulcerations and /or chronic hyperkeratosis/ proliferation. The disease often causes lameness with consequences for animal welfare and production of milk and beef. The objectives of this project are to generate knowledge about the incidence, dissemination, the etiology, and the immune response against the disease in Norwegian dairy herds.
Digital dermatitis is multifactorial with interactions between the infectious agent, the host, and the environment. Foot- associated Treponema spp. is the most important infectious agent. Data from the Norwegian Cattle Herd Recording Systems show that approximately 1300 cattle herds have had at least one cow with DD from 2014 to 2021. The disease is six times more prevalent in free-stall versus tie-stall herds. PhD student Lina Ahlèn's studies and data from the Norwegian Dairy Herd Recording System (NDHRS) show that the disease is difficult to eliminate from the herds.
Bulk tank milk (BTM) samples from 154 dairy herds, 96 from an expected high and 58 from a low prevalence area were analyzed with two ELISA tests, Medicago's ELISA, and GD Animal Health's in-house ELISA, for detection of DD-associated Treponema antibodies. The sensitivity and specificity of both tests were evaluated against herd-level claw trimming records extracted from the NDHRS. The paper «Evaluation of test characteristics of 2 ELISA tests applied to bulk tank milk and claw-trimming records for herd level diagnosis of bovine digital dermatitis using latent class analysis» by Holmøy, Ahlèn et al. is published in J. Dairy Sci. The study shows that both ELISA tests can detect antibodies against DD-associated Treponema spp. in BTM, but none of them produced satisfactory sensitivity. Currently, inspection at claw trimming is necessary for surveillance of DD in Norway even though these ELISA tests may be a useful supplement.
Lina Ahlén performed a questionnaire to dairy farmers with DD herds and to a random sample of farmers with no DD recordings in their herds, in total 380 positive and 1530 negative herds. Analyses of the questionnaire also including analyses of NDHRS data made it possible to identify differences between DD positive and negative herds. The paper «A case-control study regarding factors associated with digital dermatitis in Norwegian dairy herds» is submitted to Acta Vet Scand for publication. Free stall housing, increasing herd size, purchase of cattle, increasing claw trimming frequency, use of certified professional claw trimmer, and cleaning of the feet in the chute before trimming were associated with increased odds for the herd being recorded with DD in NDHRS. Some of these variables are risk factors while others increase the possibility for detection of the disease. Annual cleaning of the barn was associated with reduced odds of being recorded with DD.
Lina Ahlén has performed studies in 21 dairy herds with DD including clinical recordings of 937 cows and sampling of blood, milk, and biopsies from DD lesions and closely located healthy skin of 108 cows. The blood and milk samples are analyzed by Medicago's ELISA test for immune response against T. phagedenis and the biopsies by fluorescence in situ hybridization (FISH). The histopathological findings were characteristic for digital dermatitis. Only the three phylotypes T. phagedenis (PT6), T. pedis (PT11) og PT3 were identified and indicates that the diversity of Treponema spp. among Norwegian dairy cattle still is low. The paper «Digital dermatitis in 108 Norwegian dairy cows - clinics, histopathology, and humoral immune response» will be published.
Lina Ahlén has also swabbed the trimming equipment and chutes on 9 selected locations to evaluate the risk for passive transfer of Treponema spp. between herds and to investigate the effect of washing and disinfection after trimming in 22 herds. The swabs are analyzed by quantitative PCR analyses of DNA to determine the total amount of Treponema spp. and also by a quantitative PCR which identify T. phagedenis, T. pedis, and T. medium. The analyses show that T. phagedenis were found on the trimming equipment and chutes and also in biopsies from cows with DD lesions in the same herds. The study shows that washing and disinfection usually are effective, even though high maximum values indicate that the risk for passive transfer may be substantial. The paper «Treponema spp. on trimming chutes and equipment and effects of washing and disinfection» will be published in near future.
The local immune response in the biopsies collected from the DD lesions and closely located healthy skin have been analyzed by high-throughput qPCR gene expression chip (Fluidigm). Significant difference between diseased and closely located healthy skin were found. Knowledge of gene expression in DD lesions may be useful to develop more effective treatment of digital dermatitis.
Digital dermatitis is a contagious foot disease characterized by infection of the digital skin with erosions, painful ulcerations and /or chronic hyperkeratosis/ proliferation. The disease causes lameness with consequences for animal welfare and production of milk and beef. Losses are due to reduced milk production, reduced feed efficiency, reduced fertility, early culling, treatment and not being able to sell animals. Digital dermatitis is multifactorial with interactions between the infectious agent, the host and the environment. Foot- associated Treponema spp. is the most important infectious agent, but other bacteria also seem to be involved in the pathogenesis and a synergy between Treponema spp. and D. nodosus has been suggested. Digital dermatitis has until recently been seen quite sporadic in Norwegian dairy herds, but according to the recordings from professional claw trimmers in June 2016, 138 dairy herds have one or more cows diagnosed with DD. These recordings show that DD has increased rapidly during the last years. The disease is six times more prevalent in free-stall herds compared to tie-stall herds, and considering the Norwegian legislation, which demands only free-stall housing for cattle from 2034, a rapid increase in DD is expected. The planned clinical, serological, bacteriological, histopathological and molecular studies will generate knowledge about the incidence, etiology and pathogenesis of DD and the immune response against Treponema phagedenis under Norwegian conditions. The knowledge gained will support the Cattle Health Services in preventing DD, provide a basis for identifying herds that are free from the disease and for establishing regulations on trade and movement of cattle. We will be able to give recommendations that will reduce the incidence and spread of DD, to farmers whose cattle are affected. One PhD-student will cooperate with researchers in Norway and other Nordic countries.