Digital dermatitis (DD), also known as Mortellaro disease, is a highly contagious bacterial skin condition of cattle feet, caused primarily by Treponema bacteria. It is one of the most prevalent causes of lameness in dairy herds worldwide and a significant welfare concern.
Welfare Significance
Active digital dermatitis lesions are acutely painful — they are sensitive to touch, cause significant lameness, and affect feeding behaviour and social interaction. In dairy cows, lameness from DD reduces milk yield, impairs reproductive performance, and increases risk of culling. The pain caused by acute, active lesions is comparable to other conditions regarded as highly welfare-significant.
Disease Stages
The M-score classification system describes DD lesion stages:
M0: No lesion (healthy)
M1: Early, small lesion (<2cm) — often overlooked
M2: Acute, active lesion (>2cm, red/ulcerated) — most painful stage
M3: Healing lesion with proliferative tissue
M4: Chronic, scab-covered lesion — relatively non-painful but source of infection
M4.1: Acute relapse from chronic lesion
Transmission & Risk Factors
DD is highly contagious, spread by direct contact (animal-to-animal) and indirect contact (contaminated slurry, equipment). Risk factors: wet and dirty underfoot conditions, inadequate hygiene in passageways, high-stocking density, poor ventilation (increasing humidity), and introduction of infected animals without adequate quarantine.
Control Strategies
Footbathing: Copper sulphate, formalin, or buffered formalin footbath 2-4x per week. Footbath placement and management (adequate volume, appropriate concentration, regular refreshing) determines effectiveness. Formalin is effective but has significant health and safety concerns.
Early treatment: Treating M1 lesions (before they become M2) with topical antibiotics (oxytetracycline spray) under veterinary prescription significantly reduces welfare cost and prevents spread.
Housing hygiene: Regular scraping of passageways, reducing wet and dirty underfoot conditions, adequate bedding.
Biosecurity: Quarantine incoming animals, check feet before introducing to herd.