This is an archived Horseadvice.com Discussion. The parent article and menus are available on the navigation menu below:
HorseAdvice.com » Diseases of Horses » Skin Diseases, Wounds, and Swellings » Hair and Coat Problems / Itching / Irritated Skin » Ventral Midline (Belly) Dermatitis and Onchocerciasis »
  Discussion on Onchocerciasis?
Author Message
New Member:
Opie02

Posted on Friday, Aug 11, 2006 - 9:56 pm:

We have a 10 year old QH gelding that came to us late last winter. We are in the southeast and around the end of May he broke out in hives ( small bumps ) in various places around his body ( the flies were getting bad at that time so we attributed them to the flies and upped our flyspraying). A week or two later we noticed that he was losing hair in small circular ( about the size of a pencil eraser)spots on his face, underside of neck chest and inside of back legs. He has never rubbed his mane or tail but will rub these other places to the point of pinkness and even scabbing. Despite flysheets, datime stalling with fans, and fly spray he did not improve. Our vet felt it was insect allergy and gave him a depo-meDrOl shot. He seemed to get better but a month later the bald spots started to return despite treatment. This time, even with a depo shot, he is still itchy to the point of rubbing himself raw and losing hair in those same places (face chest inside of back legs but NOT rubbing mane or tail). He is on daily wormer ( Strongid) but hasn't had Ivermectin since March shots. Could this be Onchocerciasis? This seems to be related to flies/insects but maybe that's coincidental? our vet just says "insect allergy" and wants to give depomeDrOl but our flies haven't been as bad this year due to the DrOught so I am now starting to wonder. How do you diagnose Onchocerciasis?
New Member:
Opie02

Posted on Friday, Aug 11, 2006 - 10:00 pm:

P.S. He is a light chestnut which may or may not make any difference, it's just been my experience that my chestnut horses did seem to be more prone to skin irritation of various origins....
Member:
Christos

Posted on Saturday, Aug 12, 2006 - 9:12 am:

Welcome to HA, R.Wynn,

There's nothing more you can do than what DrO describes in the article.

You can try one treatment with Ivermectin, if it flames up for a couple of days and then resolves in two-three weeks, it is probably Onchocerciasis.

Presence of microfilaria on the skin, though easy to verify with a microscope, is not diagnostic. Many horses have them without being allergic to them.

The condition may spread to the eyes, so you may want to act now.

The allergic reaction may flame up significantly post Ivermectin treatment (in rare cases), so you may want to be prepared with some corticosteroid before you try it or have a vet available for the first day.
Moderator:
DrO

Posted on Saturday, Aug 12, 2006 - 11:17 am:

One other comment R.Wynn and that is it is not the large biting flies that are the problem with this type skin disease it is the small biting midges (gnats) which are much harder to see. The article on Onchocerciasis gives a link to this condition.
DrO
New Member:
Opie02

Posted on Saturday, Aug 12, 2006 - 2:36 pm:

Aren't the insect related allergies, especially the midge/gnat ones, usually associated with intense itching in the mane and tail? He has no irritation on the top side of his body, only his face, underside of neck, chest, belly line and the insides of his hind legs. We've had him put up except at night and turned out with flysheet, mask, flyspray, etc and the bug population is very low this year. He is itching so badly that he tries to scratch his face with his hind feet and rubs on anything he can find which produces bloody spots. He had a shot of depomeDrOl 2 weeks ago and it did nothing to help him.He's also on spirulina powder and I've just added diphenhydramine twice a day. But, back to my original question, would the fact that he has no irritation on his topside (withers back mane tail)point away from an insect type allergy since those places are characteristically affected with the insect type of allergy?
Thanks for your reply, I just want to help the horse, he's miserable. I did dose him with Ivermectin today ( he was just wormed with it in March and is on daily Strongid) to see if that would help.
Member:
Christos

Posted on Saturday, Aug 12, 2006 - 3:42 pm:

Onchocerciasis is insect related only as far as transmission from horse to horse is concerned. It is not a reaction to insect bites.

Onchocerca, the parasite that causes it is a nematode, a parasite that lives inside the horse. It releases microfilaria in the blood, which are then picked and transmitted by biting insects, mainly gnats and mosquitoes.

When a horse is bitten by a gnat carrying onchocerca larvae, these migrate through the blood stream in the horse's tissues, where they mature and release microfilaria, which then migrate to the skin.

The disease is hypersensitivity to these microfilaria in the skin, not the initial insect bite.

Do note that Ivermectin only kills the microfilaria. It does not kill the mature parasite, which keeps reproducing, so you'll have to treat with Ivermectin frequently to control the number of microfilaria on the horse's skin.
Moderator:
DrO

Posted on Sunday, Aug 13, 2006 - 5:57 pm:

No I would not rule out the insect hypersensitivity based on the distribution alone R. Wyn but that along with the lack of improvement with concerted effort at controlling exposure does make it less likely. For a list of possibilities and diagnostic steps see, Diseases of Horses » Skin Diseases » Hair and Coat Problems / Itching / Irritated Skin » Overview of Hair Loss & Irritated Skin.
DrO
New Member:
tilly

Posted on Friday, Jul 11, 2008 - 1:06 pm:

It seems my 7yrs OTT TB gelding has onchocerciasis. Circular bald patches on his belly, beginning to show signs on his neck and head, itchy tail and mane. Dramatic worsening of symptoms after ivermectin. I'll treat it with monthly ivermectin and hope for improvement. My question is, would this oversensitivity cause secondary symptoms? The horse is lethargic and poor looking, he has DrOpped weight and his eyes are dull. He does not seem preoccupied with scratching to the point of losing condition. He eats more good grain and hay than his buddies and grazes on good pasture but he looks worse each day. His buddies wear grazing muzzles and are bright and shiny.
New Member:
tilly

Posted on Saturday, Jul 12, 2008 - 3:09 pm:

To add to yesterdays question, I've thought of a few more. Should I continue with the once per month ivermectin indefinitely? When reading members comments it was mentioned that the eyes were vulernable, is that because they scratch them? The horse is black but his eyes are a goldish brown, I've always thought it odd now I wonder if it's a sign of something else. Any input appreciated.
Member:
scooter

Posted on Saturday, Jul 12, 2008 - 9:59 pm:

Hi Jan I don't know anything about the problem you are having, but I do know you will get more ans. if you start you own New discussion.

Hope you find ans.
Moderator:
DrO

Posted on Sunday, Jul 13, 2008 - 9:46 am:

Hello jan,
Rather than placing your post at the bottom of R Wynn's discussion if you will back up one page to the article and list of discussions, you will find much more information and if it still does not answer your question the "new discussion" button is at the bottom under the list of discussions. By posting a new discussion you will get more and faster responses. Thank you for helping us keep Horseadvice organized. If you need more information on this see, Help & Information on Using This Site » Welcome to The Horseman's Advisor.
DrO
Home Page | Top of Page | Join Us!
Horseadvice.com is a BBB Accredited Business. Click for the BBB Business Review of this Horse Training in Stokesdale NC