Table 1. Categories of exposure to cattle among study population according to duration and conditions of exposure to cattle.

Categories of exposure	Duration and conditions of exposure to cattle	Type of activity/exposure group
High	Direct contact with livestock in closed spaces	Abattoir workers
		Veterinary personal performing cattle necropsies
		Foremen
		Milkers
Medium	Direct contact with livestock in open spaces	Tractor operators
		Breeders
		Feeders
		Other veterinary personal
		Maintenance technicians
		Household contacts living in the cowshed
Low	No direct contact with livestock	Owners of the cowshed
		Administrative clerks
		People involved in commercial activities