PCR: Refinement and validation of a PCR test to replace WEC and FCLD, including commercial feasibility

Summary

The objective measurement of disease organisms in the environment and in animals will help livestock owners manage disease. The objective assessment of wool and meat quality has been important in livestock agriculture and has enabled increases in productivity. We believe that the management of animal health should also be objective and that this will lead to further increases in the efficiency of livestock production enterprises. 
The infectious organisms which cause most production loss in sheep production include the nematodes Haemonchus (barber's pole worm), Teladorsagia (small brown stomach worm) and Trichostrongylus (black scour worm) which all reside in the gastrointestinal tract but which result in different disease conditions and subsequent effects on production. Current methods for assessing gastrointestinal nematode parasites on sheep properties are not ideal, because the species cannot be separately quantified in egg counts (WEC), and the number of eggs present in faeces is not necessarily correlated with the number of larvae obtained from faecal culture (FCLD). We have undertaken work to improve the assessment of these important disease organisms, in particular, assessing the amount of parasites from different species using a DNA-based method (qPCR). The tests can identify and quantify barber's Pole, small brown stomach and black scour worms in faeces samples. 
The tests have been rigorously evaluated via the SCAHLS recommended process including comparing the results of qPCR with WEC and FCLD. These qPCR tests are now ready for pilot usage by diagnostic laboratories and managers of sheep grazing properties. A further increase in the number of tests conducted where comparison to WEC and FCLD is possible will assist in future quality assurance of the tests. In particular, further quality assurance work would be advisable for the small brown stomach worm qPCR test, which has undertaken less evaluation because of the smaller number of available samples containing this parasite. 
Furthermore, additional quality assurance using methods other than FCLD would be beneficial because of the poor relationship between FCLD and WEC. Future research work should include a field trial to demonstrate the use of the qPCR tests in a commercial setting (including cost:benefit analysis), development of additional tests which can be undertaken using the same samples (liver fluke) or for different fractions from the same samples (host DNA genotyping, parentage testing) and some scoping research to evaluate tests for important pathogens in cattle.