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Biochemical and immunological studies in sheep infected with the mite, Psoroptes ovis - OD0537

Sheep scab is an allergic dermatitis caused by the mite, Psoroptes ovis. Non-chemical approaches to the control of arthropod ectoparasites are being sought as alternative strategies to insecticidal and acaracidal chemicals which are perceived to be harmful to operator personnel and to the environment, and which will eventually select for resistant strains. On-going immunopathogenesis studies have demonstrated that experimental infestation of sheep with P. ovis results in the development of a protective immune response and support the feasibility of vaccination as a means of controlling sheep scab. Preliminary tests of extracts of P. ovis as candidate immunogens in vaccine trials have indicated that one fraction induced protection against challenge. Successful development of a vaccine strategy will be dependent on investigating dermal immunological mechanisms. Studies indicate that the persistent presence of mite antigens causes chronic inflammation leading to hyperkeratosis, parakeratosis and in some cases severe secondary bacterial infection. Differences in severity of sheep scab lesions have been observed, possibly reflecting variation in pathogenicity of strains of mites or variations in host sensitivity. Skin biopsies from outbreaks indicate large numbers of granulocytes, notably eosinophils and neutrophils. Mast cells have also been incriminated in the inflammatory process through degranulation and release of vasoactive substances. A number of mediators of mast cell degranulation are known, but their roles have not been investigated in the pathogenesis of sheep scab dermatitis. The objective of this study is to identify the precise antigen fractions responsible for providing protection against the sheep scab mite and to continue to investigate the immunological and inflammatory mechanisms associated with sheep scab dermatitis. These are essential steps towards the development of a vaccine.
01 31.03.2003 Further studies towards the identification of candidate protective antigens for P. ovis.
02 31.03.2002 Characterisation and expression of P. ovis antigens/allergens.
03 31.03.2003 Evaluation of model for cutaneous reactions of P. ovis.
04 31.03.2003 To publish the research.
Project Documents
• Final Report : Biochemical and immunological studies in sheep infected with the mite, Psoroptes ovis   (5379k)
Time-Scale and Cost
From: 2000

To: 2003

Cost: £656,725
Contractor / Funded Organisations
Veterinary Laboratories Agency
Animal Diseases              
Animal Health              
GM Non-Food              
Plants and Animals              
Sheep Scab              
Fields of Study
Animal Health