Mites are small wingless eight legged insects which occur very commonly throughout the animal and plant kingdoms. Four common skin conditions are caused by mite infections in dogs and cats, two of which can cause skin irritations in humans.
The most common canine infection caused by mites is sarcoptic mange. Veterinarians in urban practice have seen less of this disease in recent years, but it is quite common in rural areas where dogs have contact with foxes or native animals.
Usually the disease is noticeable first on the dog’s muzzle and ears. Later the legs and the trunk may be affected. Small pustular skin eruptions emerge and the hair covering takes on a mottled appearance. The dog usually is intensely itchy and may rub large areas of skin raw. Puppies often develop a very dry skin with large scales and loss of hair in tufts.
The mite burrows into the outer layer of the skin to lay its eggs. Fortunately, because it does not burrow very deeply, it is easily treated. Insecticidal washes containing Malathion are usually prescribed as these are safe. Long-coated dogs should be clipped before treatment. Washes are repeated weekly until all signs of irritation have disappeared and the hair grows again.
Sarcoptic mange causes an irritating skin rash on parts of the human body that have been in contact with the infected dog. The second form of canine mange is caused by the demodex canis mite which burrows into the deep layers of the skin.
It is most commonly found in short-haired dogs less than a year old. The first signs are usually small hairless areas on the face and the outsides of the legs. The dog does not seem to be greatly irritated unless a secondary skin infection occurs. Staphylococcal infection results in pustules and small abscess formation which causes intense itching and matting of the hair with a thick scab.
Fortunately, demodectic mange is far less common than sarcoptic mange as it is far more difficult to treat. The parasite is less accessible to insecticides and special formulations have to be used to treat severe cases. The uncomplicated disease in puppies is usually self-limiting and demodectic mange is not infectious to humans.
Cats suffer from a form of mange which attacks the skin on the outsides of the ears and the face. The cause is a mite called notoedres cati which lives in the very superficial layers of the skin. The affected areas become covered with thick yellowish scabs. The mite, which is easily controlled with normal insecticides, can produce an irritating dermatitis in humans.
The other form of mite infestation, otodectes cynotis, inhabits the ear canal of both puppies and cats. The infected animal tends to shake its head frequently and scratch vigorously at its ear, increasing the likelihood of secondary infection.
Young animals seem particularly susceptible to ear mite infections. Often a whole litter of kittens or puppies can be affected.