− | Risk factors include access to rivers and watercourses, and rodent infestation. Buying in stock, using a bull instead of AI and cograzing sheep with cattle are also significant factors. | + | Risk factors include access to rivers and watercourses, rodent infestation, buying in stock and using a bull instead of AI. Cograzing sheep with cattle can result in disease in cattle as sheep can act as non-symptomatic carriers. |