Abstract
The sheep scab mite, Psoroptes ovis, is a major problem in the beef cattle industry, especially in Belgian Blue (BB) cattle. This breed is naturally more predisposed to psoroptic mange but reasons for this high susceptibility remain unknown. Different immune responses could be a potential cause; thus in this study, the cutaneous immune response and in vitro cellular immune response after antigen re-stimulation were examined in naturally infested BB. Cytokine production in the skin and in circulating re-stimulated peripheral blood mononuclear cells (PBMC) demonstrated a mixed pro-inflammatory Th2/Th17 profile, with transcription of IL-4, IL-13, IL-6 and IL-17. Strong IL-17 up-regulation in the skin of BB was associated with an influx of eosinophils and other immune cells, potentially leading towards more severe symptoms. Virtually no changes in cutaneous IFN-γ transcription were detected, while there was substantial IFN-γ up-regulation in re-stimulated PBMC from infested and uninfested animals, potentially indicating a role of this pro-inflammatory cytokine in the innate immune response. In Holstein–Friesian (HF) cattle, generally more resistant to P. ovis infection, a largely similar immunologic response was observed. Differences between HF and BB were the lack of cutaneous IL-17 response in infested HF and low transcription levels of IFN-γ and high IL-10 transcription in re-stimulated PBMC from both infested and uninfested animals. Further research is needed to identify potential cell sources and biological functions for these cytokines and to fully unravel the basis of this different breed susceptibility to P. ovis.
Highlights
Psoroptes ovis (P. ovis), the causative agent of psoroptic mange, causes severe allergic dermatitis and intense pruritus in sheep and cattle
Previous research suggested that immune-depression was not responsible for higher susceptibility of Belgian Blue (BB), since BB animals developed P. ovis specific antibodies after infection, which correlated with the mite population density and the progression of the lesions
In HF animals, eosinophil, T-cell, B-cell and mast cell counts in the skin appeared to be higher in infested animals compared to the uninfested controls, cell counts were not significantly different between the groups (Table 2)
Summary
Psoroptes ovis (P. ovis), the causative agent of psoroptic mange, causes severe allergic dermatitis and intense pruritus in sheep and cattle. P. ovis in cattle has a more limited geographical distribution, with a hotspot in Belgium where a farm prevalence of 75% has been observed on Belgian Blue (BB) beef farms [4]. This cattle breed appears to be highly susceptible to the infection, whilst other beef breeds and dairy cattle, such as Holstein–Friesians (HF), Previous research suggested that immune-depression was not responsible for higher susceptibility of BB, since BB animals developed P. ovis specific antibodies after infection, which correlated with the mite population density and the progression of the lesions.
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