Digital Dermatitis is one of the most common infectious conditions causing lameness in cattle. It is caused by a type of bacteria called Treponemes.
The bacteria do not survive for long periods of time off the cow and so spread is generally considered to be from cow to cow. Dirty foot trimming equipment such as knives and especially brushes have been implicated in spread.
Lesions are usually found centrally around the heel bulb but can be found anywhere on the foot (and there have been treponemes isolated from udder lesions). Tissue that has been damaged by trauma or softened by long time spent standing in water/slurry will be easier for the Treponemes to invade and set up infection.
Acute lesions are often very painful, they easily bleed and the cows are usually extremely lame. Chronic lesions are less painful and tend to form long fronds of new tissue.
Give the lesion a good clean to remove as much of the overlying tissue as possible (this will likely be quite painful for the cow but allows the antibiotics to penetrate deeply where they are needed) and apply topical Terramycin spray. Ideally allow the treated cow to stand in a clean dry yard for a while after treatment.
Herd control must focus on breaking the new infection cycle. Individual treatment will help but also regular foot bathing is important to prevent new infections.
Disinfectants such as formalin (at a 5-10% concentration) may be suitable but can be painful for cows with acute lesions.
Always be conscious of this disease when buying animals in as they can be a major source of infection, especially if your own cattle are naïve.
Ideally isolate any incoming stock and put them through the footbath at least twice before they join the main herd. Ensure all foot trimming equipment is thoroughly disinfected between cows to prevent spread of infection.