CATTLE, Diseases of. Contagious Diseases.— All such diseases are communicable to other susceptible bovines by a microbe of some kind, which may be large enough to be demonstrated by a good microscope, or so infinitesimal as to remain invisible under the strongest magnifying powers (ultravisible). But all alike show their generative power by causing the disease in any susceptible animal inoculated, and this continuously so long as new susceptible subjects are presented—caus ing a plague or epizootic. Plagues of cattle present a different problem from plagues of man, in the entire absence of any moral re striction on the available modes of restricting them or stamping them out. Among the early cattle plagues in the Old World, Rinderpest stood out as the most contagious and deadly, practically all bovine animals exposed contract ing the disease, and nearly all dying. Since the beginning of the Christian era this plague has prevailed in China, Mongolia, Siberia, etc., and extended west into Europe whenever a great ruler was seized with an extension of territory mania, and involving central Europe in war, created a great demand for large army supplies and the movement of great bodies of cattle from the East. Protected by her enclosing seas Great Britain largely escaped. In the war ravaged 18th century the resulting losses in Europe were estimated at 200,000,000 head. In the 19th century active commercial intercourse largely displaced war as a cause, unduly tempt ting corrupt and corruptible dealers. In the 18th century Great Britain, writhing under her unwonted losses, fell back on the rational de vice of quarantine of infected districts and slaughter of the herds, with indemnity to the owners, and, though the effect was slow under the varying earnestness or intelligence of local authorities, the plague was eradicated. Britain's next invasion (1865) was through a cargo of cattle from Reval, Russia, and spread rapidly through the island, causing ruinous losses, until stockmen could be educated anew to the con ditions, after which it was easily stamped out, as it had been a century before. Again and again (1872 and 1878) it invaded Britain through her active commerce, from Russia and Germany, but the country already instructed and prepared made short work of it.
Another pest, lung plague of cattle, invaded the British Isles through the Dutch trade (1839) and prevailed until 1898. Being 26 years before the 19th century experience with Rinderpest, and of slower progress and less fatal, stockmen remained long obtuse to the danger and tem porized with the plague, trusting largely to inoculation from the diseased lung into the tip of the tail, where, in the absence of abundant connective tissue to accommodate the phenom enally large liquid exudate thrown out into the inflamed structures, the lesion remained cir cumscribed and the system at large had become immunized before the ultravisible germ reached the lung, its natural habitat. Though success
ful in immunizing and saving the inoculated herd this virtually spread the disease-germ in the buildings, yards, pastures, manure, fod der, etc., of the animals operated on and the pest was kept alive for 59 years, until more thorough and radical measures were adopted.
Lung plague was imported from England into Brooklyn, N. Y. (1843), into New Jersey (1847) and into Boston, Mass., from Holland (1859). The New Jersey importer stamped it out by promptly killing the whole herd; the Massachusetts authorities cleared that State by killing all infected herds at a cost of $77,511.07 for indemnities. The Brooklyn outbreak per sisted for 49 years, extending into New Eng land, New York, New Jersey, Pennsylvania, Maryland, Delaware, District of Columbia, In diana, Illinois and Wisconsin. In 1887, when the National Stock Yards, Chicago, became in volved, and the whole continent was imminently threatened, a campaign for extinction was started. In three months the plague-stricken Chicago and Cook County were cleared, and by 1892 the United States was once more free, though at a heavy cost in cattle. For long this outbreak failed to spread widely because the cat tle traffic was practically all eastward to the large cities on the Atlantic seaboard, and this plague was finally carried West by a comparatively new but considerable traffic in thoroughbreds, and in calves sent to replace losses in the Western herds. This but repeated the Old World experience that in countries breeding their native stock, as in Spain and Portugal, Norway, Scottish and Welsh Highlands, cattle remained long free from this and other plagues. The same is true of the Channel Islands. It strongly emphasizes the necessity of stopping the movement of all stock, and even men, in dis tricts where a deadly pestilence prevails, of kill ing all infected herds (sick and well) and of thorough disinfection of the carcasses, manure, litter, fodder and articles of all kinds that can by any possibility carry infection. The writer found that sterilized exudate from the diseased lung, when injected under the skin, immunizes animals against attack on exposure. If prepared without possibility of survival of the i living germ this is entirely safe and harmless, but the probable escape of the live germ, ex cepting in the most careful preparation, forbids its general use. In case of high class cattle and under skilful supervision it may be profit ably used on an already infected herd, kept absolutely separate from others.