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Reduced Worming Strategy Explained

Why use wormers at all?

Horses are wormed on a regular basis to prevent their worm burden becoming so high that it causes ill thrift and ill health in the horse. What about horses in the wild? In the UK we have ‘managed’ herds of Native ponies, so they don’t really live totally without Human intervention. Horses that do live wild are known to have much lower worm burdens than horses we keep for pleasure and work. There are some basic reasons for this:

  1. Domesticated horses are grazed on smaller areas of land
  2. Domesticated horses are grazed in closer proximity to each other

The amount of available grazing land means horses are much more likely to graze close to their dung piles and the more horses grazing together means more worm eggs being deposited on the land.

Scientific surveys have shown that where there are groups of horses on limited pastureland there are a few horses in the group that will have a higher worm burden than most of the others. The horses with the high worm burdens increase the chances of all the horses becoming infested with worms. Parasitologists and veterinarians are recommending that a more targeted approach be taken to managing worms in horses, to help prevent the spread of drug resistant worms.

Drug resistance in worms means that horses will become infested with worms and when we treat the horse with chemical wormers, the drugs will not kill the worms. This would obviously be a serious situation for horses and make it much more likely that horses become ill and die from complications, arising directly because of the worm infestations.

Another important aspect to worming horses is that they have evolved in tandem with parasite infestations; some scientists argue that trying to eradicate parasitic worms totally would actually have a negative effect on a horse’s immune system.
There is evidence for Humans that being ‘too clean’ may contribute to autoimmune conditions.

When buying chemical wormers and following a blanket worming routine be sure to use the correct dosages and the chemicals effective for the types of worms that you need to treat. Further information will be posted to P.E.T.S ‘Science Explained’ pages on wormers and the chemicals used in them. Always remember that the companies selling the worming drugs want to make a profit on their products.

Applying the Reduced Worming Strategy

Using worming chemicals less often and only for the horses that actually have a proven worm burden will slow the progress of drug resistant worms. This method is called the “Reduced Worming Strategy” or “Targeted Worming” and involves finding out if your horse(s) actually have enough worms inside them to need a dose of worming drugs. By saying, ‘enough worms’ means that even if your horse has a ‘nil’ result on a worm count test it doesn’t mean they do not have worms at all. Although the faecal (dung) egg worm count P.E.T.S performs is a scientifically accurate test, there are times when worms are ‘resting’ inside your horse, so they may not actually be producing eggs. The resting periods are part of the reason to have a faecal worm count completed on a regular basis.

When changing to the reduced worming strategy veterinarians recommend that the count be completed every 8-12 weeks for the first year. The idea behind this is to establish a reliable picture of your horse’s tendency to harbour worms. If repeated faecal egg counts show that, the individual horse is showing an acceptable level of worm infestation the count need only be performed every 6-9 months.

Advantages of the Reduced Worming Strategy

The most important advantage is that you actually know whether your horse has worms! It does not make sense to give a horse chemicals that disrupt its natural gut processes if they are not needed. Worming chemicals are extremely harsh and destroy the usual bacteria that are present in a horse’s stomach and intestines. The bacteria are important because it helps the horse digest food properly, so helping to keep your horse in good condition. The sale of pre-biotic and pro-biotic supplements shows how seriously horse owners consider their horses digestive system when working out nutritional needs.

Using the ‘Reduced Worming Strategy’ will help to prolong the usefulness of the worming chemicals we have. As the pharmaceutical companies have indicated that no new chemicals are going to be available in the near future, we need to use the chemicals we have sensibly and sparingly. Once worms develop the genes for resistance to the chemicals there is no way to reverse them, resistant type worms will reproduce at an unstoppable rate.

A well-implemented worm egg count program will save you money on your horses’ welfare and care.

Worming chemicals are harmful to insects and important beetle species that help to keep ground healthy; there is also the possibility that other animals eating insects that have been in contact with worming chemicals could be affected. If worming chemicals find their way into water courses, seeping through from the land, aquatic creatures can also be adversely affected. Using less chemicals will have a positive effect on the environment.

Limitations of the Reduced Worming Strategy

The faecal egg worm count performed by P.E.T.S is as scientifically accurate as possible but as mentioned above if worms are in a ‘resting’ or ‘hibernation’ phase, eggs will not be seen, at that point in time. Regular counts are therefore important.

All types of worm eggs can be seen under the microscope with the exception of Tapeworm ‘eggs’, it is rare to see tapeworm eggs because they usually reproduce in a slightly different way to the other types of worms. The only reliable diagnostic test for the presence of Tapeworm is a blood test, called an ELISA, which can be performed by most good veterinary practices with their own laboratory facilities or they will send tests to specialised laboratories.