Foot abscess in sheep: Evaluation of risk factors and management options

Foot abscess of sheep is a painful, suppurative and necrotic infection of the phalanges and interphalangeal joints. Sheep affected by foot abscess may be acutely lame and pregnant ewes may die with secondary pregnancy toxemia when they fail to maintain their required level of nutrition. We conducted a cross-sectional observational study to identify and quantify possible risk factors for foot abscess. A questionnaire was designed and used to conduct telephone interviews with 115 sheep farmers in the Central Tablelands of NSW in November 2012. They were asked to provide information on their farm, the animals, and management-related information for the lambing period of a selected cohort of ewes. Multivariable logistic regression analyses were conducted using two outcome variables: (a) the presence of foot abscess, and (b) low (<1%), medium (between 1% and 5%) or high (>5%) levels of foot abscess. High levels of clover in the paddocks grazed by sheep was associated with increased odds of foot abscess in both the models (binary model odds ratio [OR]: 3.18; 95% confidence interval [CI]: 1.22, 8.77 and ordinal model OR: 2.92; 95% CI: 1.35, 6.54). High risk was also associated with the farmer's observation that it had been a wet season (ordinal model OR: 7.89, 95% CI: 2.72, 24.43) and moving sheep during lambing (binary model OR: 14.15, 95% CI: 2.30, 296.61). Similarly, farms with shale/slate type soils had lower odds of the disease compared to farms with basalt-derived soils. Farmers who used foot-baths (binary model OR: 4.05, 95% CI: 1.15, 19.34) and antibiotics (ordinal model OR: 3.16, 95% CI: 1.38, 7.66) had higher odds of foot abscess, as might be expected as they adopted these measures to deal with an increased prevalence of foot abscess. The findings from this study can be used to provide extension advice to farmers and for designing further confirmatory studies.