The first thing to consider when your horse comes down with a skin condition is a little commonly ignored parasite known as NeckThread Worms or Onchocerca Microfilariae. You can find it listed in the effectiveness information found on the side of the wormer box as "Onchocerca."
The adults live in the nuchal ligament of the horse. The NL runs along the top of the neck of the horse and enables the horses to raise and lower its head. Because the nuchal ligament is not actually tissue wormer does not get to the Threadworm adults. Pretty much all horse have Neck Threadworms yet there is a wide range of the horse's reaction to the parasite from unnoticeable to very pronounced. Symptoms range from none to deep skin lesions caused by intense itching.
It is not the adults that cause the surface symptoms. When the adults reproduce the young Microfilariae migrate to the surface of the horse through the tissue. This migration affects itself in horses differently. Some develop small raised lumps, some display variously sized bald spots, some spots are itchy and rubbed raw, some occur in closely located areas, some are wide spread, and they can occur anywhere on the horse.
I have been in horses a long time and have seen a LOT of skin problems in horses labeled "allergies," "sweet itch," "summer sores," and what have you, and have seen each of these conditions diagnosed all over the board with remedy prescriptions to match from steroids to salves.
It has only been in the last couple of years that I have become aware of NTWs, NeckThread Worms, also known by their taxonomical name, Onchocerca Microfilariae, a little talked about parasite which has been around and mostly phooo phoooed since Moby Dick's great great grandparents were minnows. In my entire life I have never ever heard the word, "Onchocerca."
The eye opener for me was seeing just how effective a simple worming procedure was in making a remarkable difference in these "allergies," "sweet itch," "summer sores," and many other recurring "skin disorders."
A post appeared in my Facebook Group Marv Walker Horses about a mare that was a mass of itching sores to the point she was actually seeking out places to scratch herself. The sores were pretty much all over her body and she was incredibly distracted and difficult to handle. She would drag herself through brush seeking relief. Naturally, the group member was desperately seeking a solution to the problem as the vet's prescriptions and diagnosis, as well as those of the other horse owners she knew, weren't working.
The group chewed over the problem trying to figure out what the possibilities were and what to do about them. One by one were discarded possibilities for various reasons such as no known change to set off an allergy attack, other horse exhibiting closely resembling skin conditions to a much, much, much lesser degree than the mare, and so on.
Someone suggested NeckThreadworms, not real sure who because Facebook's archiving and searching features aren't the world's best, and a four week interval of double doses of Ivermectin.
The owner, at wit's end and willing to try anything, gave the mare two tubes of Ivermectin and very quickly noticed a marked difference in the mare's condition. In a couple weeks the mare was back to normal.
I noticed several horses at the barn I was at that had suspicious looking spots on their face, neck, shoulders and hips. They were explained away as allergies. A couple had rubbed sores on their necks and hindquarters close to their docks. Naturally, I thought, "Hmmmm..."
I was not a helter skelter wormer. I wasn't crazy about "anecdotal worming," I knew what could happen to a horse that had a massive parasite die off and I wasn't all that interested in overloading a horse with wormer without a very good valid reason. I also knew some wormers were more "dangerous" to use than others. Years ago I'd read how different wormers have different lethal doses and I decided I'd see if I could find some info about them.
So I went looking and one of the pages I found was A cheat sheet on horse wormers.
Unfortunately the wormer cheat sheet page above has been removed and I am unable to find it or another like it. I'm leaving the link as a reminder to keep looking for it.
Since we had been using Ivermectin and I noticed you had to give a LOT of Ivermectin to an adult horse to kill it and the box said it was effective against Neck Threadworms, Onchocerca Microfilariae, I grabbed a handful of tubes and a couple of the horses and dosed them up.
You want to be very careful worming horses with an unknown worming history. Horses with a heavy parasite load can experience a large toxic parasite kill with any amount of wormer that can overwhelm the body and be fatal.
Their skin "lesions" started clearing up within a day or so while the other horses' condition continued. I double dosed the other victims and got the same results.
Now, wouldn't you anecdotally be convinced NTWs were the cause?? Yeah, I know! Me too!
For the last few years I have run to the wormer box at the first sign of a skin condition on a horse and I don't recall one time the dosing did not pretty much stop the sweet itch, summer sores or allergies in their tracks. I'm not saying sweet itch, summer sores, and allergies do not occur but I certainly doubt they occur anywhere near as often as they are "diagnosed."
Surprisingly, very few people are aware of the most likely cause of their horse's skin problems.
And yes, I'm still seeing people dismiss the obvious, even many veterinarians. All you have to do is suggest NTWs and almost immediately you will get NTW denials in favor of allergies, sweet itch, bug bites of all kinds, and what have you, followed by continuous treatments of various potions, salves and prescription dosages treating the OUTSIDE of the horse..
The Disturbing Truth About Neck Threadworms And Your Itchy Horse.
Fighting The Big Fight Against Neck Threadworms..
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