1 . This thesis presents a study of the interactions between bacteria, enzymes and Psoroptes ovis, and the association between nutritional processes and P.ovis pathology. The enzymes and allergens found in mites are reviewed, and their possible roles in digestion considered.
2. Evidence suggests that P.ovis has a digestive system reliant upon acid peptidases functioning in an intracellular environment, where the actions of digestive enzymes are supplemented by involvement of bacteria. Interactions between bacteria and digestive enzymes on skin are found to be responsible for the pathological reactions in clinical P.ovis.
3. The experimental components of the thesis investigate this theoretical model by (1) investigating bacteria associated with P.ovis and the skin lesions they produce, (2) quantifying activity of enzymes associated with P.ovis and the lesions it produces and (3) experimenting with nutritional supplements (including enzymes and bacteria) thought to be essential for the survival of P.ovis.
4. Restriction Fragment Length Polymorphism studies found that the bacteria associated with P.ovis are not identical to those on the skin, implying that they originate from the mites. No single bacterial species is consistently associated with mites. Those found reduce nitrate and produce extracellular lipase, an enzyme with pathogenic effects in mammals.
5. When assessing enzyme activity across P.ovis lesions, aspartic proteinase, aminopeptidase and lipase activities were greater in infected skin. These enzymes are important digestive enzymes. The activities of lysozyme and esterase, which are front line immune response components on the skin, were greatly reduced in the infected areas. This reduction is likely due to the destruction of skin by mites, and direct damage by enzymes as mites feed.
6. In quantifying the impact of nutritional supplements on P. ovis longevity in vitro, neither gram negative nor positive bacteria extended the survival of mites, but supplements containing additional protein significantly increased survival, highlighting the complexity of the in vivo system.