Ask Horse Journal: 04/04

Heartworms In Horses
Do horses get heartworm like dogs and cats’ We were told by a vet that they no longer recommend worming horses on a regular schedule, but rather only when a fecal sample shows that worming is needed. Also, they don’t recommend changing wormers during the year, but rather use one all year and another next year. Have you heard this before’

HJ Response:

Horses don’t get heartworm, although there are a variety of equine parasites that have filarial forms that live in and travel through body tissues.

Deworming on the basis of fecal exams is a reasonable approach for healthy, adult horses that aren’t in high-exposure situations. If you do this, though, you have to realize that any time you expose your horse to a new environment, or a new animal is introduced to the group, he could pick up a load of immature parasites that can do a lot of damage before they reach the egg-laying stage and can be detected with a fecal. There are also some parasites that are difficult to pick up on fecals (e.g. bots, tapeworms), and fecal samples are only as reliable as the ability of the person reading them and may give falsely low counts if there is a delay in processing the sample (eggs hatch).

The debate continues regarding how often to rotate dewormers. Some say short intervals, others say long intervals, with no solid research available to answer the question either way. You can avoid this resistance controversy by using ivermectin or moxidectin, as there’s no proven resistance to either of these drugs, at least not yet anyway.


Hot Horse
I’ve owned my 10-year-old Quarter Horse gelding since he was four. Every summer, he gets sick, with temperatures as high as 105.9 and a loss of appetite. We have done a lot of blood work, and it comes back fine. Do you have any suggestions what might be causing this’

HJ Response:

If your blood work included complete blood counts, with white blood cell counts and differentials, and the white counts are normal in every way, that pretty much rules out an infectious problem. We’ll assume your vet has also checked for chronic infectious diseases like EIA (Coggins test) and Lyme disease.

If his only symptoms are fever and loss of appetite, it sounds like he has a temperature-regulatory problem that’s only really obvious at the hottest time of the year. Heavily muscled or overweight horses have more trouble keeping cool, as do black and brown horses. He also could be partially anhidrotic, meaning he doesn’t sweat normally. If your horse has ever had muscular symptoms that might mean he has HYPP, you should have him tested for that too. Muscles that are in spasm generate a considerable amount of heat.


Tail Rubbing
My 21-year-old Thoroughbred mare rubs her tail on her stall bars at night. She’s always done it occasionally — mostly just before worming is due or when she goes into heat. But for the past two months it’s to the point where the hair at the top of her tail is coming out in handfuls and she’s creating a bald spot on both her tail and her hindquarters. Her worming’s up to date. I’ve used a variety of shampoos and products for itching and dermititis. I’ve tried spraying it with Listerine and baby oil and various shampoos and sprays from my local equestrian shop. Nothing works. I think it’s now a habit and was considering wrapping her tail at night with Vetrap. I’ve cleaned her udder, under her tail and her rear end. I’ve checked for bruises, bites, cuts and so on. Any suggestions’

HJ Response:

Wrapping her tail is a bad idea. If it slips, it can easily cut off the circulation to the point she will lose her tail. Two possibilities here are a fungal infection or insect-bite sensitivity. Try washing the area with a tea-tree-oil-based sheath cleaner rather than a shampoo. Leave on several minutes then rinse off. After it dries, try a mixture of Calm Coat and CamphoPhenique, or a layer of Vicks over the involved skin. These provides a barrier to the midges, and they really hate the camphor. It wouldn’t hurt to have her checked by a veterinarian, both for ovarian activity and to see if she has evidence of uterine or bladder infection or vaginal irritation. Subtle conformation changes in older mares can predispose them to these problems.


Face Protection
Properly used insect repellents do a decent job of keeping flies and mosquitoes off your horse’s body, but his face and ears can be a challenge, especially with gnats and midges. A layer of mentholated rub, like Vicks, on the edges of the ears, under the eyes, encircling the nostrils and as a strip down the muzzle and between the jawbones can work wonders.

With ticks, it’s especially important to be proactive. Once a tick attaches to your horse and blows up to a size that you can easily find it, odds are any diseases it was carrying, including Lyme, have already been transmitted.

Besides keeping fields mowed and clear of brush, clip the horse’s lower legs to the knees short. Most ticks jump on board at ground level and climb up the legs under the hair. They don’t like being exposed.

Always lift the mane and thoroughly soak the roots every time you apply insect repellent, same with the base of the tail. If you consistently find ticks in the manes of horses on 24-hour turn out, consider roaching them.

Permethrin is the most effective chemical repellent against ticks. You can also create physical and chemical barriers by applying a rim around the ears or “collar” around the pasterns of either a mentholated rub or a mixture of petroleum jelly with a few cc of permethrin solution or 10 drops of CamphoPhenique. Using pine tar or a Venice-turpentine hoof dressing may also deter ticks at ground level.

Next month, we’ll tell you our top picks for fly masks and recap previous field trials in fly sprays, fly sheets and more.

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