Vaccinia

VACCINIA (from Latin vacca—cow, French vaccine, English cowpox, German Kuhpocken), natural cowpox, an infectious exanthema of cattle, occurring almost exclusively among adult females. The causative agent is a variety of the human smallpox virus, attenuated by passage through representatives of the genus Bos. (See also Vaccination, vaccines.)

Cowpox.

The local pathological process characteristic of vaccinia—a rash—is almost always localized on the skin of the udder and teats of dairy cows, as infection occurs via the hands of milkmaids who have recently had natural smallpox. In the 18th and 19th centuries, vaccinia was observed in England, Germany, Switzerland, Italy, Holland, France, and North America, most often sporadically, and less frequently in the form of small epizootics. Recently, in connection with the widespread decline of smallpox epidemics in civilized countries, cases of vaccinia have become a great rarity. Vaccination of a human with vaccinia is accompanied by persistent active immunity to natural smallpox and to vaccinia, upon which protective smallpox vaccination (see) is based. Symptoms. The incubation period is from 4 to 8 days. The rash appears initially in the form of separate reddish spots, in the place of which nodules form after 2–3 days. The latter quickly reach the size of a pea or even a bean and turn into a multilocular vesicle (pustule) of a silvery-pink color, with a metallic luster, surrounded by a halo of redness. On the 10th–12th day, the pustules reach full development, an umbilicated depression is discovered in the center, and the contents become cloudy and purulent (see figure). Soon the pustules dry up and turn into dark brown scabs, after the falling off of which a white radiant scar remains. The number of pustules is almost always small (usually not more than 20–30). The disease is benign in nature. General symptoms are insignificant: an increase in temperature of 0.5–1.0°, loss of appetite, and a drop in milk secretion. The total duration of the disease is about 20 days. The pathological process almost always remains local; generalization is observed very rarely. In these cases, the pustules, in addition to the udder, appear on the head, on the inner surface of the thighs, on the back, and on the chest. Complications (phlegmon, parenchymatous inflammation of the udder, necrosis of the teats) are encountered only with mechanical damage to the pustules, for example, during milking.