Progress in warble fly eradication

Warble flies (Fig. 1) are bee-like insects, belonging to the parasitic fly family Oestridae, which spend their entire 10-month larval period inside the body of the host animal, only emerging in the summer to complete their development to the free-flying adult stage (Fig. 2). In 1978, when almost 40% of cattle in Britain were infested, the Ministry of Agriculture, Fisheries and Food (MAFF) initiated a warble fly eradication scheme. We are now in the final stages of this plan, with infestation rates down to 0.01%. This represents a massive saving to the farming industry in terms of less damaged hides and improved production of milk and beef. It also represents an enormous improvement in animal welfare; cattle in the past often carried 20-30 of these large (2 cm long) grubs in pus-filled 'warble' lumps on their backs. Now they are never seen in most parts of the country. In this review, David Tany discusses the progress of warble fly control, warning that the problem could reappear unless stringent measures are taken o eradicate remaining foci and o control imported cattle.