Abstract
BackgroundSheep scab is caused by the ectoparasitic mite Psoroptes ovis which initiates a profound cutaneous inflammatory response, leading to the development of the skin lesions which are characteristic of the disease. Existing control strategies rely upon injectable endectocides and acaricidal dips but concerns over residues, eco-toxicity and the development of acaricide resistance limit the sustainability of this approach. In order to identify alternative means of disease control, a deeper understanding of both the parasite and its interaction with the host are required.MethodsHerein we describe the development and utilisation of an annotated P. ovis cDNA microarray containing 3,456 elements for the measurement of gene expression in this economically important ectoparasite. The array consists of 981 P. ovis EST sequences printed in triplicate along with 513 control elements. Array performance was validated through the analysis of gene expression differences between fed and starved P. ovis mites.ResultsSequences represented on the array include homologues of major house dust mite allergens and tick salivary proteins, along with factors potentially involved in mite reproduction and xenobiotic metabolism. In order to validate the performance of this unique resource under biological conditions we used the array to analyse gene expression differences between fed and starved P. ovis mites. These analyses identified a number of house dust mite allergen homologues up-regulated in fed mites and P. ovis transcripts involved in stress responses, autophagy and chemosensory perception up-regulated in starved mites.ConclusionThe P. ovis cDNA microarray described here has been shown to be both robust and reproducible and will enable future studies to analyse gene expression in this important ectoparasite.
Highlights
Sheep scab is caused by the ectoparasitic mite Psoroptes ovis which initiates a profound cutaneous inflammatory response, leading to the development of the skin lesions which are characteristic of the disease
This paper describes the use of these expressed sequence tag (EST) in the construction of a P. ovis cDNA microarray and the utilisation of this array, the first resource of its type for this economically important ectoparasite, under biological conditions to analyse mite gene expression during exposure to, and removal from, the host
Microarray construction and gene products represented on the microarray The most abundant phylum associated with the top BLAST hits for the ESTs used in the construction of the array was the arthropoda, with the most common representative species being the deer tick, Ixodes scapularis (172 ESTs or 18% of the total with significant BLAST hits)
Summary
Sheep scab is caused by the ectoparasitic mite Psoroptes ovis which initiates a profound cutaneous inflammatory response, leading to the development of the skin lesions which are characteristic of the disease. The combination of mechanical skin abrasion, mite allergen deposition and grooming behaviour by the host in response to the pruritis caused by the mites triggers the subsequent activation of a cutaneous inflammatory response [8,9] including an exudate which has been proposed to supply the mite with a food source [10]. While several mite products have been identified, including enzymes and homologues of allergens of the house dust mite (HDM), Dermatophagoides pteronyssinus and the scabies mite Sarcoptes scabiei, their functions in disease progression remain largely unknown [12]
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