Atypical digital dermatitis of bovine claw in dairy cows: clinical and histopathologic findings

Digital dermatitis is an inflammation of the skin on the bulbs of the heel which cause lameness and economic losses. Atypical digital dermatitis is a new form of an old disease which has been reported recently in the USA, UK and Netherlands.

The purpose of this study is the clinical and histopathological evaluation of claw lesions with exposed corium in cases of concurrent digital dermatitis in two endemically infected herds without preventative herd strategies for BDD.

The majority of non-healing claw lesion samples included in this study were taken from 'typical' clinical cases, namely, from lame cows examined in the course of veterinary practice by one author over a period of months in two commercial dairy farms in Iran. Fourty five lame cows with claw lesions were selected for clinical and histopathological purposes.

Examination of the affected claws revealed a topical granular appearance, painful to touch, prone to bleed with distinctive odour and extensive regional loss of the claw horn. Histologically, the epidermis was lost completely over the extension of sole ulcer lesion. The underlying dermis was intensely infiltrated by inflammatory cells, mainly polymorphic leukocytes, and in deep, newly formed capillaries were embedded in the stroma. Hyalinized thrombi were also significant in small blood vessels. In wall ulcer, there was extremely proliferative epidermis, 2-3 times with severe acanthosis and rete ridge formation. Stratum corneum was hyperplastic. The stratumcorneum were filled with neutrophils, cellular debris and erythrocytes lodged in theorthokeratotic stratum corneum.

In all the observed cases, the disorder included penetration through the horn capsule lesions to involve the corium, resulting in damage of the horn-forming cells. This new manifestation seems to be a combination of metabolic and infectious diseases.