(146.) Prevention of Leg Evil. Remove the diseased animals from the flock, and, in dressing their sores, never use a sponge, or any thing which, from its value, is apt to be preserved, and, perhaps, applied in no long time to the cuts or scratches of a healthy animal; for, though leg evil is not communicable by ordinary means, yet is it readily excited by inoculation, or the application of putrid matter to a broken surface. If the odour from the affected parts is any way offensive, wash them with, and sprinkle round the fold, either a weak solution of chloride of lime, or the disinfecting liquid of Labarraque, articles which may now be procured from every provincial apothecary. Finally, let the shepherd wash his hands carefully before going from diseased to healthy sheep, using, if need be, a little of either of these solutions; and let him look well to any injuries which his charges may receive in July, August, and September, for these are the months most favourable to the occurrence of leg evil.
(147). Inflammation caused by Maggots. The insects passing under the name of "Fly," though most troublesome in August, attack the sheep from the month of May to September, inclusive, depositing their eggs among the wool, in general about the tail, the roots of the horns, or any part which affords, from its filthy appearance, a prospect of suitable provision for the maggot. When these eggs are hatched, a process which is, in sultry weather, almost instantaneous, the maggot erodes the skin, and speedily brings the adjacent parts into a fit condition for the reception of succeeding numbers of its species.
The backs of long-woolled sheep are, from their exposure, more liable to be selected by the flies, as a receptacle for their eggs, than the corresponding parts in such as are covered by a short thick fleece.
No sooner has the maggot begun its operations, than the sheep becomes uneasy and restless, rubbing itself on stones and trees, and endeavouring, by every means in its power to free itself from the annoyance. Teazed by the constant irritation, fever soon sets in, and, if the sheep be unrelieved by the shepherd's aid, death ensues in four-and-twenty hours.
It is only lately that attention has been paid to the history of the insect pests which originate the mischief, so little damage do they appear to have occasioned in former periods. In a valuable paper, containing the result of observations made on this subject in the Highlands, and published in the second number of the Quarterly Journal of Agriculture, they are thus described:—
"The fly which is the immediate cause of this disease, seems, as far as my observations could extend, to consist of four species, viz.—the Musca Ceasar, Cadaverina, Vomitoria, and Carnaria, of Linnæus. * * *
"M. Ceasar is of a shining green colour.
"M. Cadaverina, the thorax shining bluish, the abdomen green, like the Ceasar.
"M. Vomitoria, thorax black, or dark-blue grey, abdomen dark glossy blue. This is the common Blue-Bottle or Flesh-fly.
"M. Carnaria, grey; the thorax has three black longitudinal markings on the upper surface; the abdomen is checquered, in some positions shining whitish.