Pathogenesis of Dichelobacter Nodosus and Foot Rot

Ovine foot rot is a complex, infectious condition that results in the separation of the hoof horn from the sensitive dermal tissue. Unlike other foot ailments, true foot rot is defined by the necessary presence of Dichelobacter nodosus. This bacterium colonizes the interdigital skin, but it requires the opportunistic invasion of *Fusobacterium necrophorum

• to penetrate deep into the foot tissues. In many ways, the management of this disease requires a similar vigilance to that found in managing Swine Erysipelas due to the highly infectious nature of the pathogen.

The Role of Environmental Moisture

Moist pastures act as a vector for transmission. When sheep walk through wet, muddy conditions, the interdigital skin softens, providing an ideal microenvironment for bacterial proliferation. This makes foot rot highly prevalent during the autumn and spring months. Owners must differentiate between simple interdigital dermatitis and the advanced hoof separation caused by D. nodosus. While Contagious Ecthyma (Orf) affects the muzzle and oral cavity, its contagious nature serves as a warning of how quickly flock-wide issues can spread.

Identifying Lameness and Necrotic Hoof Lesions

Clinical signs of foot rot begin with mild limping, but progress rapidly. The Leptospirosis bacterium, while not related to foot rot, serves as a reminder of how bacterial infections can have systemic consequences if not treated.

Clinical Warning Signs

• Acute lameness in one or more limbs

• Redness and inflammation of the interdigital cleft

• Putrid, characteristic odor arising from the hoof

• Separation of the hoof wall (underrunning)

• Visible necrosis of sensitive foot tissues

• Reluctance to move or graze, leading to weight loss

Diagnostic Procedures in Small Ruminants

A physical examination is the primary diagnostic tool. A veterinarian will perform a thorough foot inspection after cleaning the hoof to observe the extent of the separation. In chronic cases, the hoof becomes deformed. Unlike Rabies, which is a viral neurological threat, foot rot is localized; however, it is no less devastating to flock productivity. Diagnostic labs may perform bacterial cultures to confirm the presence of D. nodosus, especially when the disease does not respond to standard management.

Therapeutic Interventions and Surgical Management

The cornerstone of treatment is the combination of systemic antibiotic administration and localized debridement. By removing dead tissue, the veterinarian creates an environment where anaerobic bacteria cannot thrive. Similar to how veterinarians manage Kennel Cough (Bordetella) with isolation, affected sheep should be separated from the healthy flock immediately to prevent the spread of the bacteria to the pastures.

Preventive Herd Health Strategies

Prevention focuses on biocontainment. All new additions to the flock should undergo a mandatory quarantine period. Producers often use foot baths containing zinc sulfate or copper sulfate to harden the hoof horn and decrease the survivability of the bacteria. Producers often compare the biosecurity vigilance required here to Canine Distemper because of the severe impact a single case can have on the entire group.