By D.B.C. Freer-Cook. B.V.Sc, M.R.C.V.S

Dogs suffer from numerous forms of parasitic infestations, with the flea (Ctenocephalidis felis 75% C.canis 15%) being by far the most common and easily identified parasite. At the other end of the spectrum comes "Demodex canis", a microscopic, cigar shaped mite which lives exclusively in the hair follicles and occasionally the sebaceous glands of the skin. It is normal resident in all dogs' skin, passing from a bitch to her puppies shortly after birth, but fortunately only a small percentage of dogs suffer clinically from the mites' presence. The mites do not cross onto other dogs, except to the neonate (new form), nor to humans (we have our own variety), so even a terribly infested dog is not contagious to others, which is a great relief.


The clinical presentation of a dog suffering for demodicosis or demodectic mange, varies enormously, hence the alternative title to this paper. Not infrequently young dogs present with mild, localised lesions, usually on the head or limbs; small patches of reddened skin, with scaliness, hair loss and, later, increased pigmentation. 90% of these heal spontaneously, and it is believed that the dog's developing immune system manages to correct the temporary imbalance. Sadly, in a small percentage of dogs the disease develops into a generalised condition. The precise reason for and mechanism of spread is still unknown, but two distinct types of demodicosis prevail. There is the more straight forward form, with severe crusting and scaling of the skin over all or any parts of the body, accompanied by a reddening of the skin (erythema) and a variable amount of irritation. Eventually a thickened slate-blue pigmentated skin develops, somewhat like a rhinoceros hide. This is accompanied by a strong sweet and sickly odour.


The even more severe form of demodicosis comes when the mite infestation is accompanied by a secondary bacterial infection, usually staphylococci. This results in a horrendous pyoderma or pus covered skin, which is usually very poorly responsive to even intensive antibiotic therapy and, sadly, euthanasia becomes the only humane course of action. Upon examination it is often very difficult to actually find any mites, even following repeated deep skin scrapings and microscopic searches, so coming to a definitive diagnosis can be extremely difficult. However good history taking, the clinical presentation and the elimination of other possible factors, such as other parasites and contact allergies, goes a long way towards a diagnosis. Unfortunately it does not go very far towards treating the condition, which can prove to be intractable, even to the most potent shampoos.


Having made a diagnosis, either directly or by elimination, generalised or localised treatment can be started, using appropriate antibiotics, an absolute minimum of anti-flammatory steroids (they suppress an often suspect immune system) and a range of, often quite toxic, shampoos. Success is variable and recurrence is frequent, whilst the cost in both financial terms and labour is considerable.


Taking all the above into consideration, I have now used an alternative regime of treatment on four dogs, including one English Setter, with wonderful results. Supported initially with antibiotics and anti-inflammatories as necessary, I have found that serial injections of Ivomec (Ivermectin) have suppressed the condition almost completely. With an ever increasing time between injections, all the dogs have returned to an apparently normal, non-odorous, fully haired state accompanied by a miraculous re-juvination of spirit.


The drug Ivomec is not, and is unlikely ever to be licensed for use in dogs, since it frequently causes fatalities when used in all forms of collies. In fact, the Veterinary Defence Society has categorically stated that it will not support its use in the dog under any circumstance, so do not try to persuade your Veterinary Surgeon to use it willy nilly. It is, however, a very effective injectable parasiticide and if also seems to stimulate the immune system, so helping the dog to help itself. Thus, perhaps, it has a role, albeit as a last resort, when all else has failed.


Due to the tendency of developing demodicosis being inherited and, because bitches are more prone to a relapse following a season, it is advisable to spay and castrate all sufferers, in an endeavours to control this most awkward parasite.