The effect of Psoroptes ovis infestation on ovine epidermal barrier function

Abstract

Sheep scab is an intensively pruritic, exudative and allergic dermatitis of sheep caused by the ectoparasitic mite Psoroptes ovis. The purpose of the present study was to investigate the effect of P. ovis infestation on different components of the ovine epidermal barrier within the first 24 hours post-infestation (hpi). To achieve this, the expression of epidermal differentiation complex (EDC) genes and epidermal barrier proteins, the nature and severity of epidermal pathology and transepidermal water loss (TEWL) were evaluated.By 1 hpi a significant dermal polymorphonuclear infiltrate and a significant increase in TEWL with maximal mean TEWL (598.67 g/m2h) were observed. Epidermal pathology involving intra-epidermal pustulation, loss of epidermal architecture and damage to the basement membrane was seen by 3 hpi. Filaggrin and loricrin protein levels in the stratum corneum declined significantly in the first 24 hpi and qPCR validation confirmed the decrease in expression of the key EDC genes involucrin, filaggrin and loricrin observed by microarray analysis, with 5.8-fold, 4.5-fold and 80-fold decreases, respectively by 24 hpi.The present study has demonstrated that early P. ovis infestation disrupts the ovine epidermal barrier causing significant alterations in the expression of critical barrier components, epidermal pathology, and TEWL. Many of these features have also been documented in human and canine atopic dermatitis suggesting that sheep scab may provide a model for the elucidation of events occurring in the early phases of atopic sensitisation.

Comparative immune responses against Psoroptes ovis in two cattle breeds with different susceptibility to mange

“…In this study, no suppression of the transcription of EDC genes could be observed (results not shown), unlike data available in sheep. As a down-regulation of these genes in sheep skin is seen within 24 h after infection, it is possible that this was missed in this study [ 9 , 13 ].…”

“…Moreover, in vitro culture of peripheral blood mononuclear cells (PBMC) showed an increased reactivity to mitogens [ 5 – 8 ]. In general, microscopic examination of the skin from infested ruminants reveals an increased dermal thickness and a superficial, perivascular dermatitis characterised by a fast influx of lymphocytes (including γδ T-cells in sheep), macrophages, mast cells, neutrophils and eosinophils [ 9 – 12 ]. Previous work on sheep scab demonstrated an up-regulation of genes encoding for pro-inflammatory and pro-allergic mediators [interleukin (IL)-1, IL-8, IL-6] and molecules involved in extravasation of immune cells [ 13 , 14 ].…”

“…A similar pattern has been described in Sarcoptes scabiei infested mice and dogs with transcription of Th2 like cytokine profiles in lymph node cells and PBMC respectively [ 17 , 18 ]. In addition, the epidermal differentiation complex (EDC) genes filaggrin, involucrin and loricrin are significantly down-regulated in infested sheep skin, indicating an impaired skin barrier function [ 9 , 13 ] and markers of skin barrier disruption can also be found in circulating PBMC [ 16 ]. Furthermore, the systemic immune response parallels the cutaneous Th2 response as locally produced IL-4 and IL-13 stimulate PBMC to up-regulate IL-4R transcription and chemokine (C–C motif) receptor 3 (CCR3), an eosinophil activator [ 16 ].…”

“…As described for ticks [ 21 , 22 ], susceptibility of cattle to mite infestations can also vary between individual animals. Increased susceptibility in sheep seems to correlate with higher numbers of eosinophils in the skin, larger lesions [ 11 ] and potential mutations in crucial EDC components [ 9 , 13 ]. Humans suffering from severe sarcoptic scabies, better known as crusted or Norwegian scabies, show a predominant immunoglobulin E (IgE)-driven Th2 response with high levels of IL-5 and IL-13, in contrast to patients with ordinary scabies, who mainly express the Th1 cytokines IL-2 and IFN-γ [ 23 – 25 ].…”

Effects of eight vehicles on transdermal lidocaine penetration in sheep skinin vitro

“…The pre‐TEWL measurements for sheep skin in this study were similar to those reported by Stoeckli et al . () (Stoeckli et al ., ). Transepidermal water loss is not commonly measured in sheep skin, and although TEWL is a rather unreliable measure of skin integrity (Chilcott et al ., ), it can be useful clinically for pre‐ and post‐treatment comparisons (Hester et al ., ).…”