Much attention is paid to internal parasites in horses, but external parasites are not only a nuisance, but are also a source of serious health threats to horses. During cold winter months, most horse owners think that the cold will keep the parasites away, but some find happy camping grounds when hair is longer.
Long hair-coat on horse parted to reveal mite debris
External parasites such as mites are not only a nuisance, but can also be a source of serious health threats to horses during cold winter weather.
© 2018 by Dartmore Shire Horses New window.
An external parasite horse care givers should be aware of is the mite, a tiny parasites that lives in the skin of horses, donkeys and many other mammals and vertebrates worldwide. Mites are not insects but belong to the group called Acarina, together with ticks.
Mites are obligate parasites, i.e. they can neither survive nor complete their life cycle without parasitizing their hosts.
These parasites cause both minor and major irritation to both horses and owners. If a mite infection is treated too late then chances are that there are many eggs in the coat of horses. And that is the most important part, the eggs. Because these eggs only hatch when they think that the circumstances are best for hatching and this can be within two weeks, but can also be after months or a year.
There are no solutions to get rid of all the mites and the eggs in a one-time treatment. The biggest mistake horse lovers make is thinking that 1 or 2 treatments are sufficient. To get a mite problem under control it is important to understand the behavior of mites.
The following symptoms may indicate a mite infection in horses:
- Itching, especially on the legs
- Horse stomps with legs
- Horse rubs with legs
- Horse bites his legs
- Scabs and flakes on the legs
- Wounds on the legs
- Mudfever
- Thickened legs (in severe infections)
Often we see that these symptoms are first visible on the hind legs with mainly draft horses. Always check the legs for scabs, flakes and wounds when brushing.
In addition, the above symptoms apply not only to a mite infection. There are other possible causes that show one or more of the same symptoms. Itching and stomping can also occur, for example, due to changes in the feed or a bacterial infection.
For the time being there are no vaccines that will protect horse by making them immune to the mites. There are no repellents, natural or synthetic that will keep mites away from horses. And there are no traps for catching mites, for the simple reason that they spend their whole life on the animals.
There are no biological control means for controlling horse mites (or any other mites of livestock and pets).
Whereas there are numerous topical and systemic acaricides that control mites on livestock in most countries, only a fraction are also approved for use on horses or other equids. The reason is often that the horse market is smaller than the livestock market and thus it is not attractive enough for most Animal Health companies to invest in a claim for use on horses.
Some classical concentrates for dipping, spraying or dusting, containing traditional contact insecticides such as organophosphates (chlorfenvinphos, coumaphos, diazinon, etc.) and synthetic pyrethroids (e.g. cypermethrin, deltamethrin, permethrin, etc.) can control mites on horses.
Topical acaricides have a short residual effect, i.e. there efficacy does not last more than a week, if ever. And they often do not kill mites remaining deeply inside thick scabs and crusts. Therefore it is highly recommended to repeat the treatment several times with an interval of 2 to 3 weeks.
This is also important because some mite species can survive off the hosts for several weeks and re-infest the animals, and because acaricides do not kill the eggs, which will hatch and re-start the infestation.
If thick scabs and crusts are present the product should be vigorously brushed on the affected skin for the acaricide to be able to penetrate the thickened skin and reach the mites.
Edited material based on External Parasite and Vector Control Guidelines and Parasitepedia - Article previously posted on EquiMed.com in 2020.