EVERY horse owner needs to know this, PLEASE READ! - Health & Supplements - Health & Supplements - Horse Community, Horse Pictures, Horse Forum and Information

Posted : 10/16/2010 8:49:09 PM

I am guilty of being lax about worming in the past. Never again. Please read. (cross-post from another Forum)

OK, this is a spinoff on the sweet itch thread.

I have personally been shocked into believing the benefits of vigilant worming while researching sweet itch, and learning more about the parasite that is the underlying cause - not the biting midge, who is only a vector, but the worm onchocerca.

To make a long story short, the only way to control this parasite is through frequent dosing with Ivermectin and good fly control measures (which, in my experience, are never enough to keep all flies/midges off your horse at all times). The only way this parasite is transmitted from horse to horse is by the biting midge. The juvenile form has a life stage in the midge, then gets transmitted to the horse, migrates to THE SUSPENSORY LIGAMENT OF THE NECK and encysts there. It matures and releases larvae, which migrate to the dermis of the neck, wither, face, chest, shoulder, belly, and tail/ dorsal hindquarter...... basically, where the midges bite horses, so the larvae can then complete their life cycle.

The adult worms do not respond to worming medications. Only the LARVAL (microfilaria) stage responds to Ivermectin. The adult worm continues to reproduce and release larvae.

Read: a lax worming schedule does no favors here to help control this parasite. Also, other anthelmicides do not affect the microfilaria. For horses severely affected, frequent and double doses have been effective in non-clinical settings.

Also note: this parasite does not show up in fecal counts because it is not transmitted intestinally.

NOT EVERY HORSE WILL DEVELOP SWEET ITCH AS A RESULT OF INFESTATION WITH ONCHOCERCA. That is why I feel that we need to educate ourselves, and our neighbors, about this. I strongly believe that many cases of sweet itch could be prevented if more measures were taken to control infestation with onchocerca - because it might be your horse, or your neighbor's horse, who mysteriously develops sweet itch in the future after lifvng an otherwise normal, healthy life.

Here is some good reading I have dug up, after WalkingtheWalk helped get me started with my research.

Page Two of this thread has some dramatic before/right after/a few weks later pictures of a horse who suffered chronic sweet itch, and was treated with a doubled dose of Ivermectin. If you take the time to read the thread, the veterinarian poo-poo
d the onchocerca (neck threadworm) theory, but weigh the evidence in your own mind. The pictures of the poor horse mirror Crystal's condition to a T.

Horsecity.com | Keeping the Horse World Connected

more reading:

The Merck Veterinary Manual -Onchocerciasis

Efficacy of ivermectin against Onchocerca cervical... [Am J Vet Res. 1983] - PubMed result

Wormer Club - Equine & Animal Worms - About Horse Worms, Roundworms, Lungworms, Threadworms and Tapeworms (scroll down to onchocerca)

WalkingtheWalk's link:
Re: CS>CS for Equine sweet itch

and another thread worth taking the time to read, these folks are good at doing research
http://www.chronofhorse.com/forum/sh...d.php?t=155469

danastark

Posted : 10/17/2010 3:38:20 PM

Our paint gelding has "fly bite dermatitis" I was told but this could be a possibility although he doesn't demonstrate the neck issues, just extremely itchy from about April to October, scratches himself bald on his throat, chest, neck and his cannon bones. Once his winter coat starts coming in and the flies die down, he's fine? He is very thin-coated, always very sleek in the spring and summer. We've tried cortisone shots, oral anti-histimines, spirulina wafers, garlic, pretty much every fly spray known to man (watch of for Final Fly-smells like petroleum and made him peel!), fly sheets (gets too hot here for them and he was sweating to death) and the poor thing still scratches and scratches or we keep him in electric fencing so he can't ':('

Another horse person I was talking to mentioned putting ivermectin on topically? He is current on wormer although I rotate so don't always use ivermectin. Hmmmmm, I'll mention it to the vet and see what he thinks.

Thanks!

3equines

Posted : 10/17/2010 4:27:56 PM

Many of the old-school vets still poo-poo the onchocerca link to dermatitis, even though there is a lot of current, evidence-based literature supporting the theory. Also note that this worm releases MORE larvae during the peak midge season: April through October. Handy little trick of Nature, seeing that the larvae can't mature without being picked up by a midge fly.

There really is no harm in giving your horse weekly doses of Ivermectin and watch to see if the skin condition improves. Just be ready for it to look really bad after the first dose, if indeed the onchocerca microfilaria are the culprit.

danastark

Posted : 10/18/2010 12:02:56 AM

I am now very curious, although would only one horse have it out of my 4? My draft cross gets the raw ventral line but no other symptoms anywhere else, just assumed the little midges or no-see-ums were the culprits.

3equines

Posted : 10/18/2010 5:03:23 PM

Almost all horses carry the onchocerca parasite but tolerate it, their immune system can deal with the microfilaria (larval stage) in a normal way. There have been a few case studies in which horses showed lameness in the foreleg tendons and had their movement affected in the neck and cervical spine from the adult worms being encysted in large numbers, but these are exceptional cases.

Some horses become sensitized to the larvae, and develop an inflammatory reaction in the dermis of the skin, which manifests itself as sweet itch, rain rot-type patches of itching and hairloss, and the classic 'neck thread worm' dermatitis where the face, neck, chest, and ventral midline are chronically affected.

Horses with hair loss on the face, around the eyes, and in the throatlatch area show classic signs of infestation with onchocerca. In hindsight, every horse from the herd where my project Haflingers (including Crystal) had this hairloss on the face along with weepy eyes, they just didn't look healthy. Three horses in that herd have come down with full-blown sweet itch, so I believe that although the parasite exists naturally among the equine population, there is an infectious element in which populations of equines can develop the dermatitis. I would like to see more literature on the subject, but my theory is buildup of the adult worm leads to larger numbers of the larvae being released. In the particular herd I am speaking of, worming is extremely lax - maybe twice a year at most. Fly protection is also very lax, like nonexistent. It is a large herd that has occupied the same geographic location for decades, most of the horses were born there.

If any college students read this thread, and have access to scientific research articles, please give me a hand and dig up what you can find about onchocerca in equines, or neck thread worms.

AppyMom

Posted : 10/23/2010 3:10:46 AM

I have always used Equi-aid CW daily wormer on my horses. I also worm every four months with Equimax. I also use Equitrol II feed-through fly control from about March to November depending on the weather (I'm in NC). Another fly control method I use is called Quikstrike. It uses fly pheremones to attract them and when they land on the strip and ingest the 'killer' they die within seconds. The only place I've been able to find it is here and I hate being without them so I try to stock up when I order. If there is anything else I could be doing, besides passing this info to all my horsey friends, please let me know!

3equines

Posted : 10/23/2010 10:12:10 AM

Update on my own 'sweet itch' horse, Crystal.

She has been with me for 11 days, now. When she arrived, she had open, oozing, and crusty areas over her neck, shoulder, chest, hind end, tail, and belly. The areas around her neck, shoulder, and tail were extremely swollen and hot to the touch.

Right off the bat I gave everything a good bath, treated her with Equi-Spot fly control and used Sulfodene on the hot spots. I did my research on the wormer and withing a few days gave her her first dose of Ivermectin.

The heat, oozing, and most of the swelling went away with the first dose of wormer - especially the swelling on her tail and shoulders. The neck 'crest' (which is not a fatty crest but a wrinkled, inflamed crest from the worms and larvae) remained but was not as hot or swollen. The crusts began to sluff off and normal, pink skin started to show. The spot on her chest dried up. Her belly was still a mess because it had such a huge, crusty, raw area that the whole dermis of the skin was damaged. With bathing and daily application of Bag Balm the crusts began to soften and sluff off.

Four days later I gave her a second dose of Ivermectin, this time the full 1250 measure on an 800 pound horse. Two days after that the 'crest' on her neck was visibly reduced and is continuing to improve. All kinds of crusts are coming off - the skin was so extensively damaged during her outbreak that it is going to take weeks for all the dead tissue to flake off. Her belly is almost healed.

I am a believer that controlling the onchocerca parasite can make a huge difference. We have had an outbreak of biting midges in the last few days as the weather has turned warm and very humid; yet Crystal continues to get better instead of worse in their presence.