The diagnosis is easy. Psoroptic mange cannot be mistaken for sarcoptic mange, on account of the different points affected.
Psoroptic mange only attacks regions covered by wool, and sarcoptic mange those free of wool. A microscopical examination of acari removed from the diseased animals will, however, immediately remove all doubt.
Nor can the disease be confounded with phthiriasis, the trichodectes being immediately distinguished from the psoroptes by their greater size and the shape of their head. Moreover, they are usually to be found on the front portions of the shoulders.
It is more likely to be mistaken for another disease, termed by some writers seborrhœa and studied and described by Delafond under the name of sebaceous folliculitis. This disease appears mostly in autumn, and attacks animals much exposed to the weather and on moist, cold soils. It begins with very violent pruritus, followed by biting and loss of portions of the fleece. The skin is red, inflamed and painful, and the wounds are covered with large quantities of yellowish acid discharge of a sticky and offensive nature. The treatment of this disease consists in placing the sheep in clean, dry, well-ventilated sheds. Recovery is assisted by clipping and the application of some emollient dressing to the diseased parts.
The ease with which the disease can be cured and the absence of parasites enable one to readily distinguish it from psoroptic mange (scab).
Prognosis. The disease is not specially grave, so long as only a few animals are affected, for it is not difficult to cure by isolation, good feeding, and proper external treatment; but if scab appears in a flock, the freedom with which the animals intermingle is such that all are rapidly attacked, and the irritation produced at once checks their growth and causes loss in condition. Many ewes give birth to small, feeble lambs, which are almost certain to die, and in any case the wool is considerably diminished in value.
Delafond estimated that psoroptic mange formerly attacked one thirty-fifth of all the sheep in France every year, causing damage to the extent of five francs per head. At the present time, and since proper sanitary laws have been instituted, it has become much less common.
During the bad season of the year the mortality is greater, and may reach as much as from 40 to 50 per cent. In cases where scab is accompanied by some other disease, such as distomatosis, it may even rise to 80 per cent.
The treatment is preventive and curative. Preventive treatment consists in separating the healthy from the diseased animals and in disinfecting the folds, sheds, etc.
Curative treatment. The first point in this treatment consists in improving the diseased animal’s food both as to quality and quantity.