Because parasites are more abundant, small ruminants in the tropical/subtropical regions of
the world experience much greater ravages from internal parasitic disease than those in the
temperate regions. In the tropics/subtropics, the limiting ecological factor influencing the
severity of parasitism is rainfall, as temperatures almost always favour hatching and
development of the free-living stages. Attempts to expand sheep and goat production by
replacing traditional village production systems, which rarely involve anthelmintic treatment …