The Cost of Orf: Tackling a disease that is the master of deception

摘要

Contagious pustular dermatitis or scabby mouth are vivid descriptions of the relatively common parapox virus we usually refer to as orf. Unfortunately it is all too common on a number of sheep farms with costly effects on both ewes and lambs. Orf is avery successful virus because it is a master of deception. In the early stages of infection the virus confuses the sheep skin cells into producing alien proteins and growth factors that in turn cause the typical proliferative overgrowths of skin. The virus produces further alien proteins that down-regulate aspects of the sheep's immune system, so normal defense mechanisms fail to work. In a young or un-vaccinated lamb these alien factors mean that lesions can last for four to six weeks before a lamb can finally shrug off the disease.