Survival of Treponemes on Hoof Knives and Disinfection to Prevent Transmission

Digital dermatitis (DD) is an infectious foot disease of cattle, affecting a large proportion of dairy herds worldwide. The pain and lameness caused by this condition is a source of economic loss to the dairy industry and is a major welfare concern. Although many species of bacteria have been found within lesions, treponemes are the most commonly associated micro-organisms[1]. In the UK three distinct groups of treponemes have been isolated from DD lesions [1, 2]. Previous work has identified that hoof knives used to routinely trim cows’ feet are likely to carry infection and are potentially a significant means of disease transmission. When used to trim hooves of cows infected with DD, all knives became contaminated with treponemes, and an isolate belonging to the Treponema phagedenis- like spirochaetes was cultured, despite inherent difficulties in growing these organisms under laboratory conditions[3]. The risk of disease transmission during foot trimming depends on the survival times of viable treponemes on hoof knives, and the infective dose required. Disinfection of hoof knives between animals is not routinely carried out by farmers, veterinary surgeons or foot trimmers and there is currently no proven and practical disinfection regime. With the increasing use of dedicated foot trimmers working on multiple dairy farms, there is growing concern that this might be a possible route of transmission to uninfected herds. Twenty years ago, the use of a primary hoof trimmer who trims cows’ hooves at other farms, and lack of washing of hoof trimming equipment between cows being trimmed, were found to be associated with increased incidence (>5%) of digital dermatitis in herds[4]. A 2018 study of pasture-based herds in New Zealand supported these findings, and the authors concluded that farms with DD should ensure that hoof trimming equipment is disinfected effectively between cattle[5]; a view that was also supported following an epidemiological study of risk factors for increased prevalence of digital dermatitis in 39 Danish dairy herds[6]. Disinfection of hoof trimming equipment should form part of a holistic approach to DD control. The work presented here is in two parts. The first part is a survival study which assesses the risk of transmission of DD on hoof knives by testing survival times of treponemes on hoof knife blades. The second part is a disinfection study which tests a range of common disinfectants for removing viable treponemes from hoof knife blades, thereby reducing the risk of transmission of DD between cows during foot trimming. […]