The Vexing Problem of Parasite Control

030906_FamilyAffair smallIt seems like every week a new piece of information crosses my desk that makes the topic of parasite control in equines more vexing.  The top of the list of frustrating facts is of course resistance.  Most of the common parasites have shown some resistance to all three classes of chemical wormers.  Dr. Martin Nielsen, a specialist in equine parasitology at the University of Kentucky, presented what’s currently recommended regarding parasite control in a webinar for

The most important thing I learned from Dr. Nielsen is that the ‘dose by the calendar’ or interval dosing regimen has been in place for nearly fifty years, and parasites have not been eliminated.  The only thing that’s resulted is drug resistance.  We only have three classes of chemical wormers; no new ones have been developed since 1981 when the ivermectin class was introduced.  Since eradication of parasites isn’t possible, a different goal needs to be adopted.  He suggests that goal should be avoiding parasitic disease coupled with reducing or delaying drug resistance.

Dr. Nielsen recommends a two-step strategy for achieving this two-pronged goal.  The first strategy is surveillance:  do you know if your current protocol works?  Fecal egg counts can help with this assessment but cannot detect some sorts of parasites.  The second strategy is targeted prevention based on the parasites you know are challenging your equines and the characteristics of your particular equines.  For instance, foals are a special case that must be treated differently than adults.

Dr. Nielsen recently was commended by the president of the University of Kentucky for his innovative approach to funding research into a possible new dewormer.  Dr. Nielsen initiated a crowdfunding campaign to raise money.  To learn more or make a donation, click here.

Dr. Nielsen has collaborated with a number of other equine veterinary professionals to produce Parasite Control Guidelines for the American Association of Equine Practitioners.  “What is needed are properly timed treatments with effective anthelmintics administered at the appropriate time of the year, which correspond to the epidemiological cycles of transmission and the relative parasite burdens in individual horses.”  (1)  Click here to read the guidelines.

Perhaps the most vexing part of equine parasite control today is that we as equine owners have to be a lot more informed than we have been previously so that we can make the right decisions for our herd.  It’s a challenging time.  I’m grateful to Dr. Nielsen for his research and his ability to present complex information in an understandable manner.

1)      AAEP Parasite Control Guidelines, 2013, p. 2.

About workponies

Breeder of Fell Ponies, teamster of work ponies, and author of Feather Notes, Fell Pony News, and A Humbling Experience: My First Few Years with Fell Ponies. Distributor of Dynamite Specialty Products for the health of our planet and the beings I share it with.
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