Effectiveness of salicylic acid paste for treatment of digital dermatitis in dairy cows compared with tetracycline spray and hydrotherapy.

The effectiveness of salicylic acid paste (PASTE) was tested for topical treatment of 25 acute and 25 chronic digital dermatitis (DD) lesions. Control groups with the same number of acute and chronic DD lesions were treated with topical oxytetracycline spray (SPRAY) and by washing only with water (HYDRO) respectively. The therapeutic effects were evaluated using a pain score, the healing rate, the lesion size and other parameters. Pre-treatment and control examinations were carried out on day 0, 4, 14 and 21. In the PASTE group, 76.0% of acute DD lesions were pain free and 64.0% of acute DD lesions were healed on day 21 showing a normal skin surface (MO). Only 28.0% of acute DD lesions treated with SPRAY and 16.0% treated with HYDRO had healed on day 21. A significantly higher healing rate was revealed in acute lesions for the PASTE compared to the HYDRO group (p < 0.05) for all three re-checks, and for the PASTE group compared with the SPRAY group (p < 0.05) for day 4 and day 14. Healing rates of chronic DD lesions were higher in the PASTE group with 44.0% on day 14 and 36.0% on day 21, compared with 16.0% in the SPRAY and 32.0% in the HYDRO group on day 14, and 20.0% (SPRAY) and 28.0% (HYDRO) on day 21 respectively. The recurrence rate of lesions after they had healed during the study period was 14.5% in total. Digital dermatitis lesions treated with salicylic acid paste and a wrap showed significantly higher healing rates within the study period, odds ratios for healing of acute lesions with PASTE were 4.5 to 6.7 times higher than with SPRAY, and 9.3 to 36.4 higher compared with HYDRO.

Role of Vpma phase variation in Mycoplasma agalactiae pathogenesis.

Compared with other bacterial pathogens, the molecular mechanisms of mycoplasma pathogenicity are largely unknown. Several studies in the past have shown that pathogenic mycoplasmas are equipped with sophisticated genetic systems that allow them to undergo high-frequency surface antigenic variations. Although never clearly proven, these variable mycoplasma surface components are often implicated in host immune evasion and adaptation. Vpma surface lipoproteins of the ruminant pathogen Mycoplasma agalactiae are encoded on a genomic pathogenicity island-like locus and are considered as one of the well-characterized model systems of mycoplasma surface antigenic variation. The present study assesses the role of these phase-variable Vpmas in the molecular pathogenesis of M. agalactiae by testing the wild-type strain PG2 in comparison with the xer1-disrupted Vpma 'phase-locked' mutants in sheep infection models. The data clearly illustrate that although Xer1 recombinase is not a virulence factor of M. agalactiae and Vpma phase variation is not necessary for establishing an infection, it might critically influence the survival and persistence of the pathogen under natural field conditions, mainly due to a better capacity for dissemination and evoking systemic responses. This is the first study where mycoplasma 'phase-locked' mutants are tested in vivo to elucidate the role of phase variation during infection.