A field trial with a commercial vaccine against foot-rot in sheep.

A commercial, polyvalent, alum-oil adjuvanted vaccine against foot-rot was tested under conditions where climatic and management circumstances have traditionally made foot-rot difficult to control or eradicate. The vaccine had a protection effectiveness of 84.4% 120 days after the completion of vaccination. Although 93.5% of ewes developed lesions at inoculation sites, they caused no management problems. A negative correlation between foot-rot status and the development of lesions at inoculation sites was considered to show that a sheep factor exists which is related to susceptibility to both foot-rot and reactions at the site of inoculation. The nature of this factor was not determined. Vaccination was considered the easiest and most effective way of controlling the spread of foot-rot among ewes with lambs at foot in the test district.