Technical Information

The results of the 2011 round of Quality Assurance Assessments by the Western Australia Government Department of Agriculture and Food have been released. Click here to see the results for the Wormcount lab (Lab 91).

Faecal Egg Counts (FEC's) can be done on an individual or pooled basis.

• Individual samples have the faeces collected directly from the rectum of the animal and placed in a vial labelled with the tag number. This count indicates the approximate worm burden of that animal taking into account other factors such as age, sex and nutritional status of the individual. The major benefit of individual sampling is that the producer can identify particular animals that show genetic traits for worm resistance or susceptibility. Individual sampling also allows the producer to identify animals that show "average" worm burdens which are most representative of the mob, and hence the most suitable animals for future Drench Resistance Tests and FEC Reduction Tests. Although individual FEC's appear expensive en masse, in both monetary and labour terms, the information they provide can be recouped by future gains in productivity.
  Genetic resistance to worms, which may be identified with Individual FEC's, is emerging as a greater prospect for success than drenching, especially given that there is increasing resistance to combi drenches and to triple combinations of Ivermectin and white/clear drenches.

• Pooled sampling is the industry MINIMUM standard in which 10 samples are collected in the same manner as individual samples but are treated differently by being split into 2 groups of 5 at the laboratory. A sub-sample (2 grams) is pooled with the other sub-samples of the same group, giving 2 groups of combined sub-samples. To minimize sampling variability 2 separate counts are made from each group and all 4 counts reported. This reduces overall cost to the producer by reducing laboratory time.
  The limitations of this method are:
  • It only indicates if drenching is required, or if drenching has been carried out, if there has been a breakdown in drench efficacy.
  • Animals that are missed during drenching or that "spit" the drench will cause a spike in the Pooled egg count, suggesting that the drench is no longer effective when this is clearly not the case.
  • A single animal that carries a very high worm burden may cause a spike in the Pooled egg count which would suggest that drenching is required. In this scenario, over-drenching is the result.
  • Conversley, 2 very low worm burden individuals in a group of animals with borderline worm burdens may result in a low Pooled egg count, leading to drenching not being done. This would lead to under-drenching, and may cause poor thrift or death of some stock.
  • This method can NEVER give any indication of genetic traits regarding worm resistance of particular animals.

For the reasons outlined above, WORMCOUNT will treat Wormtest kits as 10 individual samples, and the cost will be $42.00 which includes a larval differentiation and, if requested, a fluke count. I encourage all producers to take that extra fraction of time to write the tag number of the animal on the labelled vial as all results will be reported on an individual basis.

In all cases, it is advisable to consider sampling more than 10 animals. There is greater statistical power in using larger population samples, and having more samples provides a fallback when re-sampling is done and previously sampled animals are found to be "empty".

Larval Differentiations are done by using the remainder of the samples not used in the FEC's and hatching the eggs in an incubator for 7-10 days at 28^oC. The larvae are collected, killed with Lugol's iodine solution and placed on a McMaster slide. The first 100 worms seen by the operator will be identified to Genera/species, and their proportions counted and reported as a percentage (%).

Further details of the above tests can be found here

Details of the Fluke Sedimentation method can be found here

This page was created on ... May 20, 2009 by John Gorham and last modified on December 21, 2012