Can a liquid bandage be used as a new treatment for infectious causes of lameness in sheep and reduce antibiotic treatment?

Lameness in sheep is a major welfare concern with a prevalence of 10.6% in England from 2004 figures, and footrot identified as the primary cause. The pathogenesis of footrot is complex and multifactorial with the primary pathology mostly related to the bacterial replication of Dichelobacter nodosus. Severity increases due to concurrent contagious ovine digital dermatitis (CODD) which is associated with treponeme infection. Footrot and CODD cases are both highly infectious and difficult to control on UK sheep farms. Injectable antibiotics are recommended for clinically lame animals accounting for two thirds of the total antibiotics used in the UK sheep industry.

Notwithstanding, an important facet of disease management is the need to rapidly curtail the spread of infectious bacteria from any sheep that do develop either footrot or CODD. Achieving this without resorting to antibiotic therapy would be of enormous benefit to both the welfare of sheep and the desirable reduction of antibiotic usage.

Robust, rapid-setting antibacterial liquid barriers (bandages) have recently been reported by Bastos et al (2020) and their use exemplified on the hooves of cattle to heal digital dermatitis. Designed, specifically, for lesions that encounter extreme conditions, such as pasture, mud, water and slurry, these barriers not only protect the wound from the environment but they retain their inherent sterile nature by contact killing bacteria that might otherwise breach the barrier or establish biofilms on it. These materials use feed grade components only, namely a natural polymer (shellac) plus copper and zinc to aid structure and provide antibacterial activity. The technology has been licensed by a spin out company of the University of Cambridge, called 'NoBACZ Healthcare'- the industrial partner for this application.

Hypothesis

Zinc-based, antimicrobial and rapid-setting liquid barriers can seal, and enable healing, of infectious lesions that lead to lameness in sheep, without the need for systemic antibiotic treatment. This approach will reduce the level of AMR bacteria carried on sheep feet compared to sheep treated with antibiotic injections.


Aims and Methods

Identification of an appropriate liquid bandage for the treatment of lameness in sheep. This will be based on zinc, as some breeds of sheep are copper sensitive.

a. A range of zinc-based liquid bandage formulations will be applied to abattoir sourced sheep feet to identify optimum application, adherence and durability properties. Swabs will be taken before and after liquid bandage application. (Y1, includes time at NoBACZ).

b. Sheep naturally infected with clinical footrot and/or CODD will be treated with the lead formulation of liquid bandage under close veterinary supervision. Swabs will be taken pre-application of the bandage and on several occasions post-application. Lameness levels will be scored at regular intervals. Sheep welfare will take priority. (Y2)


2. Investigation of the impact of a liquid bandage on levels of D nodosus on sheep feet. From swabs taken in Aim 1:

a. DNA will be isolated and total eubacteria & D nodosus will be determined by qPCR. (Y1-2)

b. Bacteria will be plated on media containing commonly used antibiotics to treat ovine lameness. Resistant isolates will be further characterized using disc diffusion assays. (Y1-3)


3. Investigation of stakeholder opinion as to the appropriateness and practicalities of treating lame sheep with a liquid bandage instead of an antibiotic injection. Initially this will be focused, with a small number of trusted shepherds, on farms that are closely monitored by a veterinarian. Where appropriate, opinion will be more widely gathered from focus groups and/or a more widely distributed questionnaire. (Y3, includes time at NoBACZ)