372 ACUTE EXANTHEMATOUS INFECTIOUS DISEASES 



countries where protective inoculation is practised, from a 

 vaccinated lamb. In rarer instances the contagion is trans- 

 mitted through intermediary agents (pelts, wool, food, bed- 

 ding, clothing of attendants, etc.). Diiring the crust and 

 desquamative stages of the disease the affected sheep are 

 especially dangerous to susceptible ones. As the wool will 

 retain the desquamated scales for several weeks, the disease 

 may be spread by a sheep fully recovered from variola, the 

 infection being carried in the fleece. Lambs are much more 

 susceptible than adult sheep. 



Intra-uterine infection, the lamb being born with the dis- 

 ease, is not rare. In other instances the lamb born of a vari- 

 olous ewe, comes into the world healthy but is an immune. 

 The period of incubation is about one week except in cold 

 weather when it may be longer. 



Symptoms. — Preceding the eruption there is commonly 

 fever (105° to 107° F.), languor, catarrhal conjunctivitis and 

 rhinitis, loss of appetite and suppressed rumination. The 

 patients seem stiff and extremely sensitive over the back and 

 loins. In one to two days on different parts of the skin 

 usually not covered by wool (eyes, inner surface of the thighs, 

 chest, abdomen, under the tail) small, dark red colored, flea- 

 bite-like spots (papules) appear which in three to five days 

 develop into lentil-sized blisters (vesicles) filled with a clear 

 fluid. The vesicles often present a depression in the center 

 (umbilicated) while some are simply flattened on top. About 

 the seventh day after the appearance of the eruption the 

 contents of the vesicles become turbid, containing pus 

 (pustule). Usually three days later the pustules erupt and 

 dry, forming in the edematously infiltrated, reddened skin 

 about them, firm, gray scabs which later become brown in 

 color. The scabs in three to five days become detached, 

 leaving a pit. All the vesicles do not appear at the same 

 time, but continue to form at intervals, materially prolonging 

 the course of the exanthema in the individual which may 

 present all the successive stages of the eruption at the same 

 time. The temperature which is high during the prodromal 

 stage, falls when the eruption develops but rises again when 

 the pustules form (secondary infection) . When the pustules 



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