Overview
Ovine footrot is a highly contagious bacterial infection affecting the interdigital skin of sheep, primarily caused by the Gram-negative anaerobic bacterium Dichelobacter nodosus. This condition is characterized by severe lameness, exudative inflammation, and in advanced stages, necrosis and separation of the hoof horn from the underlying tissue 13. It poses significant economic burdens due to reduced productivity in meat, milk, and wool production, alongside substantial animal welfare concerns 467. Early and accurate diagnosis and management are crucial in day-to-day practice to mitigate these impacts and prevent the spread within flocks 13.Pathophysiology
The pathogenesis of ovine footrot begins with the colonization of the interdigital skin by D. nodosus. Virulent strains of this bacterium express specific proteases (aprV2) that are thermostable and contribute significantly to tissue destruction 1011. These proteases degrade host tissues, leading to inflammation and necrosis, particularly in warm, moist environments that favor bacterial proliferation 89. The progression from benign interdigital dermatitis (caused by benign strains expressing aprB2) to severe clinical footrot involves the transition to virulent strains, marked by progressive underrunning of the hoof horn 115. This tissue-destructive process not only causes acute lameness but also predisposes sheep to secondary infections and chronic hoof deformities 3.Epidemiology
Footrot exhibits variable incidence and prevalence across different regions, influenced by environmental conditions, flock management practices, and the presence of virulent strains of D. nodosus. While precise global figures are lacking, studies indicate higher prevalence in temperate climates with wet conditions that favor bacterial growth 18. Age and sex distribution show no significant predilection, but younger sheep and those in intensive management systems may be at higher risk due to increased exposure 13. Trends suggest that improved management practices, including vaccination and antimicrobial treatments, have led to reductions in footrot incidence in some regions, though sporadic outbreaks remain a concern 11718.Clinical Presentation
Clinical signs of footrot range from mild interdigital dermatitis (score 1-2) characterized by swelling and mild exudate, to severe clinical footrot (score >2) with extensive underrunning of the hoof horn, severe lameness, and strong odorous exudates 13. Red-flag features include rapid progression of lesions, systemic signs of illness, and failure to respond to initial treatments, which may indicate secondary infections or complications 13. Accurate differentiation from other interdigital infections is crucial for timely intervention 15.Diagnosis
Diagnosis of ovine footrot involves a combination of clinical assessment and laboratory testing. Clinically, the scoring system outlined by the Swiss Consulting and Health Service for Small Ruminants is widely used, categorizing severity from 0 (no lesions) to 3 (severe underrunning) 114. Laboratory confirmation typically employs real-time PCR to detect and differentiate between benign (aprB2) and virulent (aprV2) strains of D. nodosus from interdigital swabs 101.Management
Effective management of ovine footrot involves a multifaceted approach tailored to the severity and flock context.First-Line Treatment
Second-Line Treatment
Refractory Cases
Contraindications
Complications
Common complications include chronic lameness, secondary infections (e.g., Escherichia coli), and long-term hoof deformities that can persist even after clinical resolution 53. Referral to a specialist is warranted if complications such as severe deformities or systemic illness arise, necessitating advanced surgical interventions or prolonged antimicrobial therapy (Evidence: Moderate 35).Prognosis & Follow-Up
The prognosis for sheep with footrot is generally good with prompt and appropriate treatment, often leading to full recovery within weeks 6. Prognostic indicators include early diagnosis, absence of secondary infections, and adherence to treatment protocols. Follow-up should include regular hoof inspections every 2-4 weeks post-treatment to ensure healing and prevent recurrence. Flock-level monitoring through periodic PCR testing can help maintain disease-free status (Evidence: Moderate 13).Special Populations
Key Recommendations
References
1 Kraft AF, Strobel H, Hilke J, Steiner A, Kuhnert P. The prevalence of Dichelobacter nodosus in clinically footrot-free sheep flocks: a comparative field study on elimination strategies. BMC veterinary research 2020. link 2 Kaseja K, Mucha S, Yates J, Smith E, Banos G, Conington J. Genome-wide association study of health and production traits in meat sheep. Animal : an international journal of animal bioscience 2023. link 3 Zanolari P, Dürr S, Jores J, Steiner A, Kuhnert P. Ovine footrot: A review of current knowledge. Veterinary journal (London, England : 1997) 2021. link 4 McPherson AS, Whittington RJ, Hall E, Cook EJ, Jones JV, Qi Ang Y et al.. A comparison of multivalent and bivalent vaccination strategies for the control of virulent ovine footrot. Vaccine 2021. link 5 Doneley RJ, Smith BA, Gibson JS. Use of a Vascular Access Port for Antibiotic Administration in the Treatment of Pododermatitis in a Chicken. Journal of avian medicine and surgery 2015. link 6 Kaler J, Daniels SL, Wright JL, Green LE. Randomized clinical trial of long-acting oxytetracycline, foot trimming, and flunixine meglumine on time to recovery in sheep with footrot. Journal of veterinary internal medicine 2010. link