This section is from the book "The Dogs Of Great Britain, America, And Other Countries. Their Breeding, Training, and Management in Health and Disease", by John Henry Walsh (Stonehenge). Also available from Amazon: The Dogs Of Great Britain, America And Other Countries.
I reproduce Mr. Youatt's description of small-pox in dogs: In 1809, there was observed, at the Royal Veterinary School at Lyons, an eruptive malady among the dogs, to which they gave the name of small-pox. It appeared to be propagated from dog to dog by contagion. It was not difficult of cure; and it quickly disappeared when no other remedies than mild aperients and diaphoretics were employed. A sheep was inoculated from one of these dogs. There was a slight eruption of pustules around the place of inoculation, but nowhere else; nor was there the least fever. At another time, also, at the school at Lyons, a sheep died of the regular sheep-pox. A part of the skin was fastened, during four and twenty hours, on a healthy sheep, and the other part of it on a dog, both of them being in apparent good health. No effect was produced on the dog, but the sheep died of confluent sheep-pox. The essential symptoms of small-pox in dogs succeed each other in the following order: the skin of the belly, the groin, and the inside of the fore arm becomes of a redder color than in its natural state, and is sprinkled with small red spots irregularly rounded. They are sometimes isolated, sometimes clustered together.
The near approach of this eruption is announced by an increase of fever.
On the second day, the spots are larger, and the integument is slightly tumefied at the center of each. On the third day, the spots are generally enlarged, and the skin is still more prominent at the center. On the fourth day, the summit of the tumor is yet more prominent. Towards the ends of that day the redness of the center begins to assume a somewhat grey color. On succeeding days, the pustules take on their peculiar characteristic appearance, and cannot be confounded with any other eruption. On the summit, is a white circular point, corresponding with a certain quantity of nearly transparent fluid which it contains, and covered by a thin and transparent pellicle. This fluid becomes less and less transparent, until it acquires the color and consistence of pus.
The pustule, during its serous state, is of a rounded form. It is flattened when the fluid acquires a purulent character, and even slightly depressed towards the close of the period of suppuration. The desiccation and the desquamation occupy an exceedingly variable length of time; and so, indeed, do all the different periods of the disease. What is the least inconstant, is the duration of the serous eruption, which is about four days, if it has been distinctly produced and guarded from all friction. If the general character of the pustules is considered, it will be observed, that while some of them are in a state of serous secretion, others will only have begun to appear. The eruption terminates when desiccation commences in the first pustules; and, if some red spots show themselves at that period of the malady, they disappear without being followed by the development of pustules. They are a species of abortive pustules. After the desiccation, the skin remains covered by brown spots, which, by degrees, die away.
There remains no trace of the disease, except a few superficial cicatrices on which the hair does not grow.
The causes which produce the greatest variation in the periods of the eruption are, the age of the dog, and the temperature of the situation and of the season. The eruption runs through its different stages with much more rapidity in dogs from one to five months old than in those of more advanced age. I have never seen it in dogs more than eighteen months old. An elevated tem-perature singularly favors the eruption, and also renders it confluent and of a serous character. A cold atmosphere is unfavorable to the eruption, or even prevents it altogether. Death is almost constantly the result of the exposure of dogs, having small-pox, to any considerable degree of cold. A moderate temperature is most favorable to the recovery of the animal. A frequent renewal or change of air, the temperature remaining nearly the same, is highly favorable to the patient, consequently close boxes or kennels should be altogether avoided. I have often observed that the perspiration or breath of dogs laboring under variola, emits a very unpleasant odor. This smell is particularly observed at the com. mencement of the desiccation of the pustules, and when the am mals are lying upon dry straw.
The friction of the bed against the pustules destroys their pellicles, and permits the purulent matter to escape; and the influence of this purulent matter is most pernicious. The fever is increased, as also the unpleasant smell from the mouth, and generally the faeces. In this state there is a disposition which is rapidly developed in the lungs, to assume the character of pneumonia. This last complication is a most serious one, and always terminates fatally.