Traditional worming schedules - based upon regular worming with anthelmintics (wormers) was introduced by vets in the 1960's to prevent disease caused by Strongylus vulgaris (one of the large redworms). Disease from this worm is now exceedingly rare, however little has changed in the way in which we use schedules to worm horses in Australia.
This excessive use of wormers over time has resulted a number of types of worms becoming resistant to our most common wormers. Given that there are no new active ingredients for wormers on the horizon it’s time to re-think your worming strategy.
Currently, there are three recognised treatment strategies
- Interval dosing
The traditional way of worming with the wormer being administered at regular intervals according to the normal worm egg reappearance period for each drug. Dosing period is indicated on wormer packaging. All animals should be wormed at the same time. It is this system of worming that has resulted in widespread resistance due to the constant ‘survival of the fittest’ pressure on worm populations. However, in situations where horses are constantly moving on or off a property or where there are large numbers of young horses it may be the most practical strategy. Every effort should be made to reduce the intervals at which wormers are administered.
- Strategic dosing
All horses are dosed at strategic points in the season based upon consideration of likely worm burdens. Timing will be influenced by factors such as climate and careful consideration needs to be given to all factors that influence the likely level of infection. Additional dosing may be administered at strategic intervals to remove worms such as tapeworms. This system is more suitable for horses that stay mostly on the property, adult horses known to carry low worm burdens and where the worm paddock contamination, and risk of infection can be better estimated. This is a very good means of reducing the use of wormers, and hence resistance, but requires more attention to detail than interval dosing. The financial savings with reduced use of wormers can be considerable.
- Targeted dosing
Horses are only treated when it has been demonstrated that they carry a large worm burden. This involves performing regular faecal worm egg counts on all animals and treating animals with an egg count above a pre-determined level, normally between 200 and 500. This system is only suitable for adult horses where they spend the majority of time on the property. It also requires a commitment to be diligent in collecting faecal samples. However, in well managed systems the costs of testing are generally less than the costs of treating on an interval dosing strategy.
Interested in changing your strategy? With EasyWormer we provide strategic and targeted dosing programs aimed to help you reduce the number of wormers used and put a halt to resistance on your property. You can view our programs here.
The information in this article was sourced from the National Animal Disease Information Service http://www.nadis.org.uk EasyWormer recommends a fecal egg count before and after worming to determine the effectiveness of wormers and the level of resistance (if any) on your property and to consult your veterinarian before undertaking any worming program.