Plant cysteine proteinases as new anthelmintics to treat sheep GI nematode infections. (360G-Wellcome-086479_A_08_Z)

We recently undertook a pilot study on efficacy of papaya latex in treatment of a sheep infected with Haemonchus contortus and Trichostrongylus colubriformis. Following oral administration the burden of H. contortus and T. colubriformis was 41% and 12% less than in an untreated animal. In a third infected animal administration of the same dose into the abomasum gave 87% reduction in H. contortus but 0% reduction in T. colubriformis. We consider these results achieved under non-optimised conditio ns sufficiently encouraging to merit further study. Using the same parasites and oral administration of the active fraction from papaya latex and pineapple juice we will confirm or deny efficacy by producing dose-response curves for the effect of these plant extracts on worm burden. Doses will be quantified in terms of moles of active enzyme. Read-outs will be faecal egg counts and worm burdens, with microscopy to analyse the conditions of the worms before and after treatment. To test the hypoth esis that a neutral pH environment in the abomasum will increase efficacy we will choose a sub-optimal dose from the above experiment and co-administer Cimetidine. A separate animal will be cannulaterd to allow the abomasal contents to be sampled for pH and enzyme activity.