Abstract
A footbath-based control program for ovine footrot, a contagious disease caused by Dichelobacter nodosus, will be implemented in Switzerland. The currently used footbath disinfectants formaldehyde, zinc sulfate and copper sulfate are carcinogenic or environmental pollutants. Hence, the aim of this study was to identify alternative disinfectants, which are highly effective, non-carcinogenic, environmentally acceptable, inexpensive, available as concentrate and suitable for licensing. The antimicrobial effect of a series of potential chemicals such as lactic acid, propionic acid, hydrogen peroxide, sodium hypochlorite, octenidine dihydrochloride, chlorocresol, Ampholyt 20 and the registered biocide DESINTEC® Hoof Care Special D (Desintec) were investigated by culture based in vitro testing. The microcidal effect of various Desintec concentrations were then compared against routinely used 4% formaldehyde and 10% zinc sulfate in ex vivo assays on sheep feet from slaughter. For this purpose a newly established PMA (propidium monoazid) real-time PCR using the improved dye PMAxx™ was applied that allows discrimination of viable and dead D. nodosus. In the ex vivo experiments, 4% formaldehyde was significantly more effective than 10% zinc sulfate and was chosen as positive control for assessing the new disinfectant. The disinfectant effect of Desintec in a minimal concentration of 6% was equally effective as 4% formaldehyde, meaning that it offers a comparable antimicrobial effect against virulent D. nodosus. In conclusion, Desintec is a promising disinfectant for replacing formaldehyde, copper sulfate and zinc sulfate in footbaths against footrot.
Highlights
Dichelobacter nodosus is a gram-negative fastidious anaerobic bacterium and the causative agent of ovine footrot [1]
The aim of this study was to identify an alternative disinfectant solution, which is highly effective against D. nodosus, non-carcinogenic, environmentally acceptable, inexpensive, available as concentrate and suitable for licensing as biocide for treating footrot in Switzerland
Results for each disinfectant with the corresponding reduction of virulent D. nodosus are given in Table 3 for triplicate testing and S1 Table for single testing
Summary
Dichelobacter nodosus is a gram-negative fastidious anaerobic bacterium and the causative agent of ovine footrot [1]. Clinical symptoms start as early as 2 weeks after first contact and the disease leads to pain, lameness, decreased meat and wool production as well as animal welfare issues [4,5,6]. In Switzerland, costs for management and growth reduction without control measures were estimated at CHF 172.3 million for 2014–2030 [7]. To address these problems, various countries started to develop and implement footrot control or elimination programs [3]
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