Equine pastern dermatitis: a narrative review on clinical presentation, diagnosis, risk factors, prevention, and therapeutic approaches

Abstract

Equine pastern dermatitis (EPD) is a nonspecific cutaneous reaction pattern on the distal extremities, typically in the palmar/plantar area of the pastern. Although EPD is commonly seen in equine practice and can be a debilitating condition, peer-reviewed original studies on many aspects of this multifactorial syndrome are still scarce. This narrative review aims to give an overview of the clinical presentation (forms of EPD and clinical scores and differential diagnoses), risk factors, and therapeutic approaches. The emphasis is on intrinsic and extrinsic risk factors as most of the original work has been published on these aspects. The available data supports the effects of age, breed, and breed-related phenotypical traits (draft breeds with feathers and large cannon circumference) on the frequency and severity of EPD manifestations. Hind legs and unpigmented limbs are also more frequently affected. Genetic effects in draft breeds appear to be complex, and no commercial genetic tests currently exist. Evidence for meteorological effects like rainfall and humidity is inconclusive. Associations with Chorioptes infestation and bacterial microbiota imbalances but not with fungal infections have been consistently shown. Causality has not been demonstrated for specific infectious agents. Original studies have investigated the effects of antibacterial agents (Kunzea oil, phytosphingosines, and triclosan), fatty acids, aromatic oils, and humectants as well as therapeutic approaches to Chorioptes infestation in EPD-affected equids. While therapy remains largely empirical, knowledge of investigated risk factors for this multifactorial syndrome can inform diagnostic and therapeutic approaches. Raising owner awareness of EPD could be key to improving the welfare of affected horses.

Pastern dermatitis outbreak associated with toxigenic and non‐toxigenic Corynebacterium diphtheriae and non‐toxigenic Corynebacterium ulcerans at a horse stable in Finland, 2021

“…A recent review on equine pastern dermatitis by Gerber et al. (2023) also summarizes bacterial findings associated with the condition. While other corynebacteria, such as C. pseudotuberculosis and Corynebacterium jeikeium were described in standard bacteriology, diphtheria‐like organisms were not.…”

Environmental impacts of equine parasiticide treatment: The UK perspective

“…Although it is not authorised for use in equids, topical fipronil is commonly used off-licence in horses as a treatment for chorioptic mange ('leg mange') (Gerber et al, 2023), as there are no drugs authorised for use in this disease in the horse. Dermatitis of the cannon and pastern regions is commonly encountered in feathered horses incuding Cobs and Heavy Horses, and a proportion of these animals will be affected by chorioptic mange ('feather mites') (Gerber et al, 2023;Yu, 2013).…”

“…Although it is not authorised for use in equids, topical fipronil is commonly used off-licence in horses as a treatment for chorioptic mange ('leg mange') (Gerber et al, 2023), as there are no drugs authorised for use in this disease in the horse. Dermatitis of the cannon and pastern regions is commonly encountered in feathered horses incuding Cobs and Heavy Horses, and a proportion of these animals will be affected by chorioptic mange ('feather mites') (Gerber et al, 2023;Yu, 2013). The environmental impact of the veterinary use of fipronil in dogs and cats has received recent media attention with a joint policy statement from the BVA, BSAVA and BVZS issued in 2021 (BVA, 2021) urging an end to blanket use in small animals.…”

“…As the Chorioptes bovis and Chorioptes equi (the usual causes of chorioptic mange) are not host-specific and can survive in the environment for several weeks, these aspects should be considered by treating all in-contact animals (Gerber et al, 2023). Stable hygiene (such as removing bedding and decontamination of the stable surfaces) is another important component of the control of chorioptic mange to prevent re-infection, and antiparasitic drugs should not be relied on as the sole treatment.…”