What Exactly Are Feather Mites?
Chorioptic Mange Mites, more commonly known as feather mites, are a skin surface dwelling mite that feeds mostly on skin debris. While Chorioptic mites do not burrow into the skin, they can cause considerable irritation in horses. The set of symptoms feather mites create is commonly known as Pastern Dermatitis.
Although they can occur in any breed, feather mite infestations appear to be much more prevalent in the heavy horse breeds, likely because the feather creates an environment ideal for mite growth and reproduction.
Signs & Symptoms of Feather Mites
Common signs that may indicate the presence of feather mite are chewing on the leg or foot, consistent stomping of a particular foot, scratching one leg on another and scratching on gates, water troughs and fences.
Symptoms of feather mite include reddening of the skin, crusty scab like lesions, hair loss, itching and irritation, skin thickening and lower limb swelling. In severe cases, particularly when the horse has been rubbing or chewing the effected areas, oozing, open wounds and secondary fungal or bacterial infections can occur. (1).
The scab-like lesions most often occur on the outside and inside of pasterns, bulbs of the heel, back of the fetlock and side of the cannon, but it is important to note that mites can live anywhere on a horse. According to Paterson & Coumbe, “Chorioptic mange caused by Chorioptes bovis is a common pruritic skin condition of the horse which usually affects the lower legs (leg mange) but can present as a generalized skin disease.” (2).
Feather mites can be quite difficult to get rid of because they can survive for months wherever they find skin debris – stable bedding and floors, rugs, saddle blankets and even grooming equipment. (1).
How To Tell If Your Horse Has Feather Mites
The easiest way to identify whether or not your horse has feather mites is to part the feather at the back of the leg (in several different places) and look for the skin irritation and debris typically caused by a mild case of feather mites. You can also ask your vet to do a skin scraping, but you’ll need to shave the feather in order to do that properly.
Here’s an example of healthy feather:
You can see that while there is some dirt in the hair, there’s no debris caused by mites and no skin irritation.
Here’s an example of the debris in the feather that is common when mites are present:
This debris will look slightly different on each horse and will often have a hair going through the centre of it, so won’t brush off easily like dirt will. It can be close to the skin or slightly down the hair strands, as seen in the picture above.
Irritated skin generally appears bright pink, or even red, like this:
You can see that there is also some debris in the hair in this example.
Left untreated, feather mite can develop and be much more painful for the horse, with lots of sores and irritation, like this:
Here’s an example of the small scabs often present under the feather if the horse has been scratching, rubbing or chewing on their legs. These are much easier to see once the feather has been removed.
The feather on a horse with feather mites will often look like it is not in good condition (dry, matted) as in the photo below.
Here you can also see a spot where the hair has been rubbed short – if you parted the hair you’d likely find a scab/irritated skin there.
A few more examples of a horse with feather mite…
You can see the debris, irritated skin and even a sore in these pictures.
Guidelines For Treating Feather Mites
Once you’ve determined that your horse has feather mites, you’ll need to decide on your next steps. Here’s a few rules to follow…
1. According to Paterson & Coumbe, “The mite’s life cycle is approximately 3 weeks and is completed on the host; however mites can survive for up to 69 days away from their host.” (2). In short, if you want to eradicate feather mites it is critically important to make sure you treat all horses on the property, thoroughly clean all stables and equipment and rest potentially infected pasture for a minimum of 12 weeks. If you do not do all of the above, the horses you’ve treated will simply get feather mites again.
2. Clean the horse’s skin, especially around any scabs or sores, to remove dead skin cells before treatment. This reduces the places for mites to hide and also interferes with their food source.
3. Plan to apply the chosen treatment multiple times. Doing so will significantly increase the chances of success. Washing and topical treatments should be repeated once a week for a minimum of four weeks.
NB: Most medical practitioners will recommend completely removing the horse’s feather to increase the effectiveness of treatment. Once the leg is hairless, treatments can be applied with better accuracy and penetration of treatments is improved. However, our experience has been that feather takes quite some time to grow back and when it does it’s rarely the same as it was prior to shaving. It is important to note that you can effectively treat feather mites without removing the hair, as long as you’re prepared to be patient and thorough when applying treatments.
Treatment Options
Ivermectin
Ivermectin is another commonly recommended treatment for feather mites, but there is little research to back up its effectiveness. One study found that while it reduced the symptoms, it did not completely eliminate mite infestations. Here’s an excerpt:
“A comparative study using fipronil spray in a 0.25% solution and doramectin given at a dose of 0.3 mg⁄ kg on two occasions 14 days apart by subcutaneous injection revealed both drugs to be effective in eliminating behavioural signs in affected animals. Although mite numbers were significantly reduced in both groups neither drug completely eliminated mites and there was no improvement in the appearance of the lesions themselves. In a further study, ivermectin paste, given orally, was investigated using three different protocols. All of the horses improved. However despite waiting 3 weeks after therapy to assess the horses there was no significant change in their clinical scores. The advantage of systemic medication is that it negates the need to clip off hair from the pasterns and overcomes the difficulty of applying topical applications on what are often fractious horses. Despite the improvement seen in these studies, none of the drugs completely eliminated mites.” (3).
Another study with a smaller sample group found Ivermectin and Moxidectin effective in treating Chorioptic mites and added that their results “indicated moxidectin oral gel is effective and a good alternative for the treatment of Chorioptic mange in horses to avoid drug resistance that may develop as a result of the intensive use of ivermectin alone for long periods.” (4).
As mites only feed on the surface of the skin, it’s possible that they don’t experience the full effect of drugs given to the horse either orally or by injection and thus are not completely eradicated when such treatments are used.
We have used Dectomax (Ivermectin injectable) to treat feather mites in our own herd many times. Our experience has been in line with what the study above suggests – it provides relief to the horses, but does not completely solve the mite problem.
Dectomax is not particularly expensive per horse, but can represent a significant investment up front because it only comes in 500ml bottles. You’ll need about 40ml to treat an adult horse – two doses of 20ml two weeks apart. If you have a few horses, this isn’t such an issue, but if you’re a single horse owner it may be worth speaking with other heavy horse enthusiasts to arrange splitting a bottle. The cheapest place to buy Dectomax is on eBay!
NB: Most of the injectable Ivermectin/Doromectin treatments recommended are an off label use of the product and can cause allergic reactions in horses. Check with your veterinarian first or use at your own risk.
Selenium Sulphide Shampoo
One study conducted on a quite a small sample found that Selenium Sulphide shampoo effectively treats Chorioptic mange (feather mite) in feathered horses. The horses were washed head to toe with the treatment three times, each five days apart. The treatment was a mixture of two parts water, one part shampoo and was left on the horse for ten minutes before being rinsed off. During the study the horses were turned out into paddocks that had been rested for two months. They were tested again after the third treatment and no evidence of mites could be found on skin scrapings. Follow up months later revealed no evidence of re-infestation.
NB: Selenium Sulphide shampoo can cause reactions in horses with particularly sensitive skin, so test on a small patch first.
Fipronil
Fipronil is the main ingredient in Frontline spray, which is a product marketed for controlling fleas and ticks in dogs and cats. Previously, this was quite an expensive way to treat feather mites because Frontline was the only Fipronil product on the market, but their patent has expired and cheaper brands are now available.
Fipronil relieves the symptoms of feather mites but does not completely eradicate an infestation.
“Although therapeutic trials have shown it is successful in alleviating clinical signs, it has been shown to significantly reduce but not eliminate parasites and in studies has not produced any statistical improvement in lesion score.” (2).
We’ve used Fipronil on our own herd more than once – much like Ivermectin it has been successful in providing relief for the horses but doesn’t always completely resolve the problem. Some of it’s strong points are ease of availability and application – you can buy it in any pet store and it’s easy to apply on a horse that is sensitive about its legs being touched. We spray three to four squirts onto the skin (lift hair out of the way) on the back of the fetlock.
Pig Oil
Pig Oil, a mixture of white mineral oil and yellow sulphur powder, is one of the most common methods for treating feather mites. It is widely used on all feathered horses in the UK. This treatment dates back hundreds of years and gains its name from the pig farmers who used to apply it all over their pigs to kill mites.
According to Scott & Miller, sulphur is “an inexpensive, effective treatment of infestations of non-follicular mites in the horse. It is fungicidal, bactericidal, keratolytic and antipruritic. Its ability to penetrate lesions due to its keratolytic action, as well as its anti-parasitic and antipruritic action makes sulphur an excellent topical medication to treat Chorioptic mange.” (5).
To make Pig Oil, put half a cup of yellow sulphur in one litre of white mineral (paraffin) oil. Mix well until the powder is dissolved in the oil. Apply the Pig Oil to the horse’s legs starting above the knee or hock and working your way down. Take care to achieve complete coverage of hair and skin, massaging well into any areas with scabs or sores. Do this once per week for at least four weeks.
While no studies have been done to prove the efficacy of using Pig Oil to treat feather mites, the fact that it has been around for so long and is used so widely indicates it must be effective.
Lime Sulphur Dip
In a 2009 study to evaluate the effectiveness of shampooing and lime sulphur solution in treating Chorioptic mange (feather mites), researchers tested horses that had been unsuccessfully treated with Fipronil and Ivermectin.
Some of the sample group were clipped while others were not and several different treatment methods (with and without shampoo) were applied. All horses in the study received the lime sulphur dip.
Lime sulpur dip is made from calcium hydroxide, sulphur and water. Researchers applied a solution of 97.5% diluted to a 5% wash. That is, 50ml of lime sulphur solution in 1 litre of water. The horses were washed and then had the treatment solution applied via spray bottle to wet hair. The solution was left on the horse – not rinsed out. This treatment was applied once a week for four weeks.
Following treatment, nearly all of the horses achieved the lowest possible pruritis (itching) score, with only two showing mild signs of pruritis. Skin scrapings taken after treatment did not find any evidence of mites.
Since all of the horses across the different groups were treated with the lime sulphur solution, researchers stated “some horses in Group A were neither clipped nor shampooed, and were treated only with lime sulphur. The fact that these horses also responded to treatment suggests that the lime sulphur may have been the most important element of treatment.” (2).
The specific type of lime sulphur dip used in the study above is not currently commercially available in Australia, but it is possible to obtain a permit to import it for personal use. To do so, you’ll need to get a recommendation from your vet and then contact the Australian Pesticide & Veterinary Medicines Authority.
References
1) Pugh, D.G., Hu, X.P. & Hughes Bourke, K. Control of Chorioptic Mange Mites on Horses, Donkeys, and Mules; Alabama A&M & Auburn Universities.
2) Paterson, S., and K. Coumbe. An Open Study to Evaluate Topical Treatment of Equine Chorioptic Mange with Shampooing and Lime Sulphur Solution. Vet Dermatol 20:623-629, 2009.
3) Rendle, D.I., Cottle, H.J., Love, S. & Hughes, K.J. Comparative Study of Doramectin and Fipronil in the Treatment of Equine Chorioptic Mange. Vet Record 161:335-338, 2007.
4) Osman, S.A., Hanafy, A. & Amer, S.E. Clinical & Therapeutic Studies on Mange in Horses. Vet Parasitol 141:191-195, 2006.
5) Scott D.W. & Miller, W.H. Parasitic disease. In: Equine Dermatology. Philadelphia: WB Saunders, 2003; 321–75.
6) Curtis, C.F. Pilot Study to Investigate the Efficacy of a 1% Selenium Sulphide Shampoo in the Treatment of Equine Chorioptic Mange. Vet Record 144: 674-675, 1999.
