Introduction : Treponema phagenedis is one of the main anaerobic bacteria responsible for digital dermatitis or Mortellaro's disease in cattle. It is an infectious and inflammatory skin disease, very contagious. In dairy cows, this disease is endemic and is considered a serious problem that compromises animal health and productivity worldwide. The standard diagnostic procedure for digital dermatitis is the observation and control of foot lesions, and their classification into 4 progressive stages (M1 to M4), which requires restraint of the cow. The presence of specific anti-Treponema antibodies has been shown to be associated with digital dermatitis. A diagnostic kit allowing to measure these antibodies and to give a prevalence in dermatitis of the herd was developed allowing the epidemiological follow-up intra-herd.

Materials and Method : An indirect ELISA has been developed, using a recombinant antigen for the detection of antibodies against Treponema phagenedis in bovine milk tank. The BioLisa® kit Bovine Digital Dermatitis Ab reagent has been validated by a study in dairy farming. The tank milks (mean of 70 cows) were analysed after observation of the feet. The OD values obtained were transformed into positivity values.

Results and discussion : The study on different cheptel has shown that there is a good correlation between this positivity values and the prevalence of the disease in the cheptel.
And after reconstitution of the mixture with increasing prevalences, mixtures of positive milks (lesions described) in negative milks (no lesions), an interpretation of the thresholds of positivity in prevalence could be confirmed.
The BioLisa® kit Bovine Digital Dermatitis Ab reagent, allows fast, simple and practical detection of digital dermatitis in dairy herds. It is an epidemiological investigation tool for the management of digital dermatitis, which gives the prevalence in herds.
The use of a new diagnostic test for health monitoring can prevent the spread and exacerbation of the disease and can support decisions in terms of conservative measures.