PSX-29 Evaluation of a vaccine in sheep to control foot rot in the Southeast

Abstract Foot rot in sheep is a condition that can affect performance and well-being. Reactive therapeutic injectable antibiotic treatment (RTA) can be effective at resolving foot rot but often requires serial treatment of animals. RTA does not facilitate the animal industry goals of decreased antibiotic use in food producing animals. Our object was to evaluate if vaccinating ewes against foot rot prior to the onset of a wet season would decrease the number of ewes that experience foot rot, the number of ewes treated, and the number of treatments in affected ewes compared with RTA only. At weaning, Suffolk and Texel ewes (n = 80) were blocked by breed, age, foot rot status, and body weight (BW). Ewes were randomly allocated one of two treatments: Control ewes were monitored for foot rot and administered RTA to treat foot rot symptoms, or Vaccine ewes were administered a foot rot vaccine and boosted 42 d later and subsequently monitored for foot rot symptoms. Ewes were scored for foot rot using an index of lameness, incidence, and severity scoring. An index score of 3 indicated a foot rot event and resulted in RTA of intramuscular administration long acting oxytetracyline. Ewes not responding to the initial RTA received a macrolide antibiotic administered (Tulathromycin or Gamithromycin) at the label dose. Body weight and body condition score (BCS) were collected from ewes on d -1, 0, 51, 134, and 185. Locomotion, incidence, and severity scores were collected on the same dates. Ewe BW, BCS, and were analyzed using the Mixed procedure of SAS. Incidence of locomotion, incidence, severity, treatments, and index were analyzed using Glimmix procedure of SAS to determine odd ratio estimates. Neither ewe BW nor BCS were affected by vaccination treatment (P ≥ 0.85). Control ewes were 2.35, 1.96, 1.83, 2.23 and 2.69 times more likely (P ≤ 0.008) to have greater locomotion, incidence, severity, index scores respectively, and were 2.69 times more likely (P = 0.001) to require RTA compared with ewes that were vaccinated. Total cost for RTA were $110 greater for Control than Vaccine group because of a greater number of treatments. However, total costs and $/ewe cost were greater for the Vaccine group because of vaccine and RTA costs. The value of decreased incidence of foot rot in the Vaccine group is not captured in this analysis. The foot rot vaccine decreased the measures of foot rot and fewer RTA in vaccinated mature ewes, which supports the food animal industry goal of decreased antibiotic use. However, the price of the vaccine does create an economic disincentive unless other economic benefits can be valued.