Are We Deworming Too Often?
The Horse Trust from the UK has issued a call to "stop over-worming". They've launched a campaign to get horse owners to take a "more informed and strategic approach" to deworming because of the growing problem with resistance to dewormers. Now's a good time to do this because many people start more aggressive deworming programs in the spring.
There's no doubt that parasites are a potential problem in horses and that dewormers are an important part of parasite management. However, good parasite management and frequent use of dewormers are not synonymous.
Drug resistance in parasites doesn't get a lot of attention, particularly compared to drug resistance in bacteria. However, there is increasing evidence that resistance to dewormers is a problem in some regions, including right here in Ontario. It may actually be a very widely disseminated problem, but we don't know the full extent of it because testing parasites for resistance isn't as easy and routine as testing bacteria.
People often think that they are providing excellent management by deworming their horses very frequently. Just like people are starting to pay attention to the concept of prudent of use antibiotics, we need to think about prudent use of dewormers. These are important drugs and we need to make sure that we don't contribute to their demise.
- Deworming should be done according to a program developed by you and your veterinarian. There is no "standard" program because the needs of different facilities and horses vary.
- A good deworming program isn't necessarily a frequent one.
- Fecal egg counts are a test of a horse's manure to look for parasite eggs. This type of testing can (and should) be used to determine who needs to be dewormed, and testing after deworming can be used to detect resistance to dewormers.
- Decreasing the use of dewormers can help reduce the risk of resistance and save you money at the same time. How many other things that are good for you save you money as well??
- There are other very important management practices, such as pasture management, that play an important role in parasite control. Trying to rely on solely on drugs is bound to fail in the end.
Photo: An adult roundworm (Perascaris equorum) from a horse.
