Mite bites
Leg mites are horribly aggravating for affected equines and can be a recurrent problem. Karen Coumbe MRCVS explains how best to tackle them
FEATHER mites – or leg mites – are among the most stubborn of equine parasites, causing a condition commonly called heel mange (chorioptic mange). This typically affects breeds or types with plentiful feather such as cobs, Shires, Clydesdales and Friesians, and some native ponies.
Horses that are suffering from these mites will typically stamp their hooves, and bite or rub their lower legs. With time, severe crusting and scaling of the skin develops, with skin thickening and general swelling. This can become infected and is debilitating. Irritation is usually on the lower limbs, although it can spread over the body. All four legs can be affected, but the condition is often worse on the hindlegs.
The degree of sensitivity varies between individual horses, and an allergic reaction may be involved, similar to flea-bite allergies that affect dogs. This means that even if only a few mites are present, they can cause much irritation.
The disease can be compared to the human skin disease scabies, which can occur when groups of people live in close contact.
ERADICATION OPTIONS
DIAGNOSIS is not difficult – the challenge is how to eliminate the mites. Prompt, effective control is key, although this can be difficult when horses are reluctant to have their sore legs handled. Clipping the horse’s feathers drastically increases the chance of success, although understandably some owners are reluctant to do so.
Treatment options should be discussed with your own vet, as there are several options but no single magic cure.
There are currently no licensed medications for treating these mites for horses. Most cases are treated with either topical washes or injections, combined with active decontamination of the horse’s environment.
An approach to achieve decontamination and prevent reinfection should include:
● Emptying stables of bedding and fastidious cleaning of boxes, grooming equipment and rugs.
● Ideally, treat any other horses that have been in contact with the affected individual (although it is rarely feasible to treat every horse in a large yard).
● Crucially, be vigilant with all individuals beyond the 10 weeks that the mites can persist in and around stables (see box, left).
● Adopt quarantine measures and repeated prophylactic (preventative) treatment with a wash or shampoo.
● Susceptible horses seem to be reinfected easily, so limit their exposure to untreated individuals.
● Work with your vet to ensure there is a sensible management programme with effective environmental decontamination for your whole yard.
REASONS FOR CAUTION
WITH regards to treatment using washes or injections, the former are the more benign option, being safer and so preferable by far. Washes and shampoos do require some extra effort to use, but the pros outweigh the cons.
Many other treatments involve repeated injections with dewormer products, which are licensed for use on sheep and
cattle, or sprays using chemicals, some of which contain powerful products designed to treat fleas in small animals. However, most medications require repeated usage. Widespread usage of dewormer drugs causes worm resistance, making these products less effective and causing a bigger problem for equine health.
They also have serious sideeffects for the wider environment. There is evidence of ivermectin products excreted in horse droppings being insecticidal and having persistent effects in the environment for months. Similarly, scientific reports show that some deflea products designed for dogs and cats, but also used on horses, can kill invertebrates when the chemicals reach our rivers. Debate is ongoing as to whether the use of these products should be restricted.
The risks of using anti-mite injections that need to be repeated makes them a questionable approach, so my plea is to think twice about using them.