Lameness outbreak in a muddy cattle kraal
On a communal farm near Grootfontein, 45 Bonsmara-cross cattle are kept in a kraal that has been muddy for two weeks. Seven animals are lame; two have a swollen space between the claws, a foul smell and a fissure leaking pus. One has a temperature of 40.3°C and is off feed. The herd was vaccinated against anthrax and botulism last month; there is no salivation, no vesicles in the mouth, and no sudden deaths. The owner has a bottle of oxytetracycline (20% long-acting) and a copper sulphate footbath. A neighbour advises putting all cattle through the footbath daily for a week, giving every animal oxytetracycline, and culling the worst case. The farm sells milk to a local informal market and slaughters cattle for home use.
1. Give the most likely diagnosis and explain how you would distinguish it from foot-and-mouth disease and interdigital dermatitis using the history and signs.
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Most likely foot rot (interdigital necrobacillosis), caused by Fusobacterium necrophorum invading damaged skin between the claws in wet, muddy conditions. The signs fit: swelling between the claws, foul smell, pus, fever and lameness in several animals. Foot-and-mouth disease is the key exotic disease to exclude. FMD usually causes vesicles and erosions in the mouth and on the feet, drooling, and rapid spread; it is notifiable. There is no salivation or mouth lesion here, but because FMD can vary, the owner should isolate lame animals and report suspicion to the veterinary authority before treating the whole herd. Interdigital dermatitis is usually milder, with superficial dermatitis and less fever. A vet should confirm if cases do not respond.
2. Evaluate the neighbour's advice. Include drug withdrawal and antimicrobial stewardship.
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The neighbour's advice is partly right but too broad. A copper sulphate footbath can help dry and disinfect feet, but daily use for a week can be harsh on skin, corrosive to equipment and polluting in runoff; use it as directed by a vet, and stand cattle on dry bedding afterwards. Blanket oxytetracycline is not good stewardship: treat affected animals early, at the correct dose, and consult a vet. Respect withdrawal periods for milk and meat; the farm sells milk informally and slaughters at home, so treated animals must be identified and kept out of the food chain until the label withdrawal ends. Culling the worst case may be justified if the claw is deeply infected or chronic, but not as the first response. Improve drainage and isolate new cases.
3. Design a prevention plan for the next rainy season.
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Prevention should target mud and skin damage. Grade and drain the kraal, add a raised dry mound, and move feeding and watering points so cattle are not standing in slurry. Reduce stocking density and rotate holding areas. Keep a footbath at the entrance, but use it correctly and not as a substitute for drainage. Check hooves regularly, treat early cases promptly, and isolate lame animals. Vaccination is not a standard control for foot rot; hygiene and early treatment are more important. Monitor new cases weekly during the rainy season.