Nematode parasites pose the greatest current threat to agricultural productivity and animal welfare. Subclinical worm infections cost the UK sheep industry over £84 million a year. Currently most anthelmintic treatments are given to entire herds or groups of animals following a treatment regime that is not based on any diagnostic or epidemiological information. This approach is not sustainable since it promotes the spread of anthelmintic resistance and there are concerns with regard to food residues and environmental impact. However, effective anthelmintics remain vital in controlling parasitic gut worm populations. The International PARAsite SOLutions (PARASOL) project was established to try and develop low input systems for farmers across the globe to adopt in order to sustain the effectiveness of the available anthelmintics.

 

Anthelmintic resistance has been diagnosed in many countries world-wide. Scientists at Moredun Research Institute in Edinburgh showed in a survey in 2000 that 80% of lowland farms in Scotland had parasites that were resistant to the white drenches (benzimidazoles), whilst other surveys in South Africa show that only 1 anthelmintic from 7 tested had an efficacy of the recommended 95%.

 

The PARASOL project looked at two ways of targeting anthelmintics to reduce drug usage and leave a proportion of parasites in refugia (unexposed to any drug); targeted treatments (TT), in which the entire flock is treated based on diagnostic information and targeted selective treatments (TST) where only those individuals within the herd who will benefit in some way are treated.

 

In trials conducted by Moredun Research Institute in Edinburgh, it was shown that the use of anthelmintics is dramatically reduced by using a TT or TST approach. The group also showed that the use of a TST approach could reduce anthelmintic usage by 50% compared to whole flock monthly treatments, whilst still maintaining similar levels of animal performance.

 

This can lead to a number of advantages for farmers, not least a substantial reduction in costs because less anthelmintic is required. A study of 8 participating farmers who used a targeted treatment approach showed that each saved an average of over £600.

 

However, Dr Frank Jackson, Principal Research Scientist at Moredun and member of the PARASOL project thinks that the biggest advantage of using TT and TST approaches is the effect it should have on slowing the development of anthelmintic resistance. “By treating less animals, a proportion of the worm population is kept in refugia, i.e.unexposed to any drug. This should allow the worm population in the environment to remain susceptible to the drug and slow down the development of anthelmintic resistance.” He added “Another advantage is that, by carrying out regular monitoring on flocks, any signs of anthelmintic resistance can be picked up at an early stage.”

 

Other recommendations from the project are complimentary to the UK SCOPS initiative, but through PARASOL these recommendations will now be accepted throughout Europe as ‘gold standard’ methods to manage anthelmintic resistance. These include: