In the long history of human-animals relationships, a few episodes stand out in which one species has made a significant contribution to the survival of another. Rarely do cats get credit for such an accomplishment--more often dogs or horses, and then, usually in times of war--but the Black Plague of Europe is one of those times.

By way of background, the ancient Romans, in their conquest of Egypt, had brought cats home to Europe. Cats subsequently suffered a period of disfavor during the superstitious Middle Ages, for they had become associated with witches and the Devil; some people believed black cats were witches in disguise, or that they assisted witches in performing their craft. Those who kept cats as pets were the objects of much suspicion, and widespread cat hunting led almost to their extinction.

When rats from Asia brought the bubonic plague to Europe via trading ships in the mid-1300s, the epidemic (variously known as the Black Plague, the Great Plague, the Black Death, and the Great Mortality) swept across the continent, resulting in devastating loss of human life. In all, one-third of the population of Europe--some 34 million people--died. In England alone, more than half the human population perished; in some parts of France, ninety percent.

It took the authorities some time to figure out the cause of the problem. At one point they tested the theory that the disease was being spread by dogs and cats; thus the mayor of London ordered the execution of all such pets. Despite the extermination of millions of companion animals, however, the plague did not abate but actually accelerated, for, of course, the elimination of all cats was soon followed by an explosion of the rat population.

Eventually it became evident that people who had kept cats, in violation of the law, fared better; for the cats, according to their nature, killed the rats that carried the fleas that really carried the plague. People slowly began to deduce the rat-flea-disease connection. When the truth finally came to light, cats were quickly elevated to hero status, and soon became protected by law.

The Great Plague ended when the fleas started dying, as a part of their natural life cycle, in the cold of fall and winter. Subsequent plagues would visit Europe over successive generations, and other continents suffered similar outbreaks; it would not be until the 19th century that scientists really began to understand the epidemiology of the plague. Increased sanitary conditions over time helped reduce its incidence, and with the discovery of antibiotics in the 20th century, the threat of the plague was greatly reduced.

Would it be a stretch to say that, by bringing the rodent population under control, cats saved humans from extinction? At least, European humans? At a minimum, cats deserve credit for heroically saving the species that, through ignorance, almost wiped them out.

(C)Lisa J. Lehr 2006