Worm Egg Counts and Drench Resistance Testing

Mt Barker Veterinary Hospital has been involved in faecal worm egg counting and drench resistance testing since 1985, and has trained, accredited laboratory staff who process the samples.


Faecal worm egg counts (WEC) are a valuable tool in determining the worm burden of your animal and to ensure drench treatments have been effective. We routinely perform WEC in sheep, alpacas, horses and cattle.



Current recommendations from the Western Australia Agricultural Department are to minimise unnecessary drenching in flocks. Faecal WEC are the most effective way of maintaining good worm control without increasing selection pressure for drench resistance. Monitoring also indicates whether drenching has been effective and the level of parasite contamination being deposited in a paddock.


Performing A Faecal Worm Egg Count

1) Collect 12-15 individual samples of faeces from a mob.

This is done either in a raceway directly from the rectum or by holding the mob in a corner of a paddock, moving them off, and then collecting 12-15 different fresh samples.The samples need to be collected into separate bags making sure the air is excluded. If samples are to be delivered to the veterinary hospital the day of collection they can instead be stored in egg cartons.

2) Note the sheep type i.e. from ewes, weaners etc, when they were last drenched and with what product, also when they are due to lamb or be weaned.

3) If samples are not going to be submitted to the veterinary hospital straight away they need to be stored in the fridge, not freezer.


Once your samples have been processed by our trained staff, results and recommendations for drenching will be faxed / phoned / emailed to you. On most occasions the turn-around time for this whole process is the same day.


Drench Resistance Testing

Drench resistance testing examines the effectiveness of individual drench types on each worm type present in a group of animals. It is the most accurate way to test for drench resistance and we commonly use the procedure known as Worm Egg Count Reduction Test or WECRT. Drench resistance testing should be conducted on each property every 2–3 years or when you suspect there is a problem with worms in your flock.


Please contact us to discuss drench resistance testing for your property.