Treating only clinical cases

Dose only the animals in the flock/herd that appear to be clinically affected. These animals will be acting as a source of infection for the rest of the group. Follow the guidelines for anthelmintic use. Early diagnosis of clinical signs and good farmer awareness are required for successful use of this strategy.

This strategy is based on two principles:

1 In some farms, subclinical production losses are unavoidable and/or not significant to the farmers income perception. In these cases, the cost of routine drug treatment may outweigh the benefits that the farmer will achieve from their use. It is therefore better for the farmer to invest in treating only the animals which will benefit most from treatment. (It may also be found that particular animals are requiring treatment more often, in which case it may be more economical to slaughter these individuals).

2 Where long periods of the year offer good conditions for larval development, treating the whole flock/herd whenever a few clinical cases appear will lead to the rapid development of anthelmintic resistance. Treating only the clinical cases reduces the proportion of the worm population that is exposed to drug selection pressure, slows the development of resistance and ensures that effective drugs are available for the future.

Clinical treatment against fluke may be effective in chronic conditions, however acute fluke can be caused by infection with large numbers of young flukes. Most of the readily available flukicides on the market will not be effective against immature flukes and may not have the desired effect when used on acute cases. Triclabendazole should be used in such circumstances.