The Fight Against Dewormer Resistance: What Can You Do?

Life at times is rather complex – and requires us all to adapt. Adaptability is a valuable trait in evolution that has been endowed by nature to many of the organisms present on earth.

Most of us are aware of the growing problem of the resistance of various forms of bacteria to certain antibiotics. Doctors now are administering counteractive medications when the situation deems it necessary. You should not be surprised when these medications are targeted against parasites. As they, too, have adapted well to the medication-drenched environment that surviving is not a problem for them. And for horse owners, this could be a major problem.

What Happens in Drug Resistance

In the different equine parasite species, there will be one that develops genes that makes them invulnerable to certain deworming agents more than other kinds. Once they survive a deworming routine, they will move on to the next phase – breeding. They will be lucky enough to pass down their “advantageous” gene. The sad fact is that the parasites with the gene advantage tend to increase while those that do not develop resistance tend to diminish in numbers.
The results then become obvious – the so-called equine dewormers that we use become less and less effective. This is due to the increased survival rate of the worms from resistance. It is always advised that using a different class of deworming agent helps to increase success rate of killing the parasites.

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Be Careful with Your Favorite Deworming Agent

Because you have discovered that a compound like Ivermectin has been so effective in eliminating unwanted worms, you may decide to stick to it. While it may be tempting to do so – don’t. This can develop into a problem of parasite resistance. These resistance problems are not innate – they develop. Which means that these parasites mutate over time in a specific population. These mutations can be beneficial to the organism (because it allows them to become resistant to medications). However it can be a serious health threat for the host.

Dewormer resistance is now a global problem. The patterns could differ from one country, region, or farm to another.

The Value of Fecal Egg Count Test

Parasite resistance is a serious problem for many horse owners. Fortunately, fecal egg count tests can be performed to identify if your farm has been affected by the problem. This test measures the parasite egg count in your horse before and after administering the deworming agent to see if the particular agent is effective in treating parasite infestation.

It is important to understand that fecal egg count testing should be performed before you think about giving your horse any deworming medications in order to have a basis of information that you can compare with.

For instance, you are using a benzimidazole (fenbendazole) class of wormers and you will expect that there will be a 90% reduction rate in the egg count. If the results show that the rate is lower than that, there is a possibility that resistance has inflicted your farm – at least to that specific class of wormer.

The fecal egg count test is an important tool to assess how great or less of a problem resistance is to your specific location. Keep in mind that it’s best to ask your local veterinarian for help when it comes to doing this particular test and getting advice based on the results.