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Mange

( Sarcoptic & Notoedric)

Squirrel with mange.


Description and Distribution

Mange is a skin disease of mammals caused by a tissue-burrowing arthropod, the mange mite. A variety of mange mites exist; the ones most often identified as the cause of mange in Michigan wildlife are Sarcoptes scabiei and Notoedres centrifera. The mites are too small to be seen with the naked eye, but skin changes brought on by infestation can be dramatic. The skin diseases caused by these species of mites are sarcoptic and notoedric mange.

Sarcoptic mange has been reported in a wide range of mammals nationwide. In Michigan, sarcoptic mange has been reported in red fox, coyote, gray wolf, porcupine, black bear, cottontail rabbit, and raccoon. Notoedric mange has been reported in North America and in Michigan in the eastern fox squirrel and the gray (black) squirrel. There is some question as to the specificity of the mites causing mange on the various species of wildlife. Some parasitologists believe the mite is specific for the host on which it is found. Other parasitologists challenge this belief because there are records of transfer from fox to wolf and dog, rabbit to monkey, goat to man, dog to man, etc. It appears that sarcoptic mange mites are less host-specific than originally believed allowing for an infestation to occur on a dog that has contact with a mangy wild canid. Notoedric mange mites are host specific for squirrels and are not transmissible to either canid or feline pets.

Transmission and Development

Sarcoptic and notoedric mange mites spread to new hosts through direct body contact or by transfer from common nests and burrows. Stages in the life cycle include the egg, larva, 2 nymphs and the adult. The parasite lives and burrows in the skin layers. Fertilized females deposit eggs as they tunnel through the skin, and the eggs hatch in 3 to 4 days. Males complete their development in 13 to 16 days, females in 18 to 23 days. Fertilization apparently takes place when the female is in its final stage of development.

Clinical Signs

Sarcoptic mange is characterized by thinning and loss of hair, thickening and wrinkling of the skin, and scab and crust formation. Red foxes are the most severely affected, exhibiting a thinning of hair accompanied by accumulations of foul-smelling, wet, crusted exudate about the head, and in severe cases, over much of the trunk and legs. In advanced cases, animals are emaciated and weak.

Notoedric mange results in hair loss, first over the chest and shoulders (see illustration), but progressing over the entire body. In extreme cases nearly the entire body is bare and the exposed skin becomes thickened and dark. There is no crust formation on the skin of the squirrels.

Pathology

Sarcoptic mange is a serious disease in many animals. Severe infections result in drastic changes in the skin and evidence of ill health in the host. The disease seems particularly pathologic to foxes, especially in pups in the summer. The hair becomes sparse, the skin inflamed and irritated. Tissue serum and pus resulting from bacterial infection in the damaged skin combine to form a thick, odorous crust over the affected areas. Skin changes around the eyes, ears and mouth may cause blindness, impaired hearing and difficulty in eating. The disease is often fatal to red foxes. Notoedric mange is a serious disease of squirrels, especially during the winter. Large areas of the body or the entire body becomes denuded of hair and the animal may die from exposure because of the loss of their insulating layer of fur. Spontaneous recovery with full restoration of the hair coat is frequently observed in squirrels.

Diagnosis

Mites are generally abundant in the skin and in the moist exudate about the involved areas. Tentative diagnosis made from clinical signs should be confirmed by examining skin scrapings under a microscope for the presence of mites.

Treatment and Control

Sarcoptic and notoedric mange can be effectively treated by orally administering Ivermectin to infested individuals. Contact a local veterinarian to inquire about purchasing the Ivermectin from them to treat the animals. If label directions are followed for the appropriate dosage, a food item can be laced with this compound and made available for consumption by the infested animal. For most wildlife species it will likely be difficult to treat an infested animal but this procedure is feasible for semi-tame squirrels commonly observed in urban areas.

Elimination of mangy animals to reduce opportunities for transmission of the parasite is sometimes suggested. The effectiveness of this procedure is questionable, because the parasite is likely widespread before infestations become obvious.

Significance

Severely infested animals show distinct signs of poor health, and mange has proven fatal to wild animals on numerous instances. A marked decline of foxes in several states has been attributed to mange. Mange appears to be a contributing factor, if not a primary one, in squirrel mortalities in cold weather.

Sarcoptic mange mites are known to transfer from animal hosts to people, so persons handling mangy animals should take reasonable precautions: wear rubber gloves if possible, and always wash promptly after handling a diseased animal. Freezing kills the mites; therefore it is best to freeze carcasses that are collected for examination.

Notoedric mites are not transmissible to humans.


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For questions about wildlife diseases, please contact the Michigan DNR Wildlife Disease Laboratory.