Demodex canis is a mite that lives in the hair follicles of canine skin and is present in small numbers in most healthy dogs, horses and even humans. Transmission occurs from the bitch to nursing pups by direct contact during the first 2 or 3 days of neonatal life. However, in certain dogs these mites can multiply on the skin to become a condition known as demodicosis, or demodectic mange. The condition is more common in purebred dogs and certain breeds have far more frequent disease than others, but any breed can develop the disease.
SEVERITY: Mild to Severe depending on the type of infection.
There are two types of clinical conditions seen with demodicosis:-
1. Localised demodicosis is usually seen in young dogs and commonly occurs on the face and forelegs. The condition often heals spontaneously but this type of demodicosis may also progress to the generalised state.
2. Generalised demodicosis covers a large area or large patches of the body and secondary bacterial infection is common. There are three forms of generalised demodicosis:
i) juvenile onset: usually starts between 3 and 18 months of age. If the lesions do not resolve spontaneously or receive adequate treatment, the patient carries the disease into adulthood.
ii) adult onset: the dogs are generally over 5 years of age and an underlying disease or immunosuppression (with the demodex as a secondary problem) should be suspected.
iii) chronic pododermatitis where the disease is confined to the paws. These cases are particularly resistant to therapy.
A complete cure for the generalised form of the disease is not always possible. In these cases, lifetime therapy may be necessary for control.
Demodectic mange is diagnosed by taking a skin scraping to demonstrate the nature and quantity of mites in the skin of the dog. The microscopic debris and hair collected are examined under the microscope where the immature forms and eggs are visible. Sometimes a skin biopsy may be required under general anaesthesia.
Localised demodicosis is a mild disease that usually heals spontaneously in 6-8 weeks, but may wax and wane in a localised area for months.
Generalised demodicosis is a more serious form of the disease and is difficult to treat. In the case of adult onset generalised demodicosis it is always necessary to search for predisposing factors such as Cushing’s disease, neoplasia, or other medical diseases causing immunosuppression etc. The dog will be placed on a nutritionally balanced diet with vaccinations and heartworm preventatives kept current. Any significant stresses should be removed. Corticosteroids are contraindicated in all cases of demodectic mange.