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Biochemical and physiological studies to identify potential targets for the control of Psoroptes ovis - OD0536

The aim of this application is to understand the digestive and nutritional physiology of the sheep scab mite and the interaction between mite, host and bacteria as essential prerequisites to in vitro culture and identification of control target molecules. Sheep scab is an allergic dermatitis caused by the mite, Psoroptes ovis. Non-chemical approaches its control are being sought as alternative strategies to insecticidal and acaracidal chemicals, which have proven harmful side effects on farmers and will eventually select for resistant strains. Information on the basic physiology and biochemistry of mites in general and P. ovis in particular is sparse. This project will build on our current contributions to understanding the biochemistry of digestion and the role of bacteria in midgut function and pathology, taking a systematic approach to providing a detailed description of mite nutritional physiology and molecular characteristics of digestion. Following an exhaustive literature review, we will further characterise the digestive enzymes produced by P. ovis and define the contribution to the digestive process by bacteria present in the scab site. Critically, we will test the hypothesis that scab pathology results from extra-oral digestion, whereby mites graze upon a skin surface modified by its own digestive enzymes and bacteria. The model will include nutritional information from a unique dataset, correlating natural pathology with fleece composition.The results will be applied continuously to the development of mite in vitro culture, focusing upon mimicking the conditions in vivo, and exploiting the continuous supply of mites from VLA. In vitro-raised mites will be used in pioneering assays to test enzyme inhibitors and protective antisera for anti-mite activity.
01 28.02.2001 Review existing knowledge on mite digestive physiology.
02 31.07.2002 Characterisation of the biochemical enzymatic activity of mite digestion.
03 31.07.2002 Define the role of excretory/secretory products in extra-oral digestion.
04 30.06.2002 Investigate the role played by lipase-producing bacteria in the mite midgut on the digestive physiology of the parasite.
05 31.12.2001 Establishment of optimal nutritional feeding requirements of sheep scab mite.
06 31.05.2003 Identification and development of techniques for improving the in vitro culture of sheep scab mites.
07 30.06.2003 Evaluation of selected potential targets for immune, chemical and biological control strategies.
Project Documents
• Final Report : Biochemical and physiological studies to identify potential targets for the control of Psoroptes ovis   (1255k)
Time-Scale and Cost
From: 2000

To: 2003

Cost: £384,341
Contractor / Funded Organisations
Veterinary Laboratories Agency
Animal Diseases              
Animal Health              
GM Non-Food              
Plants and Animals              
Sheep Scab              
Fields of Study
Animal Health