In all the previous wars of history, the louse had killed more men that had ever died from bullets, swords, or other weapons. Would this war be a repetition of the history of the past? Would lice stop the advancing American Army and kill thousands of our fighting men? Things looked black! Over a million poverty-stricken people were crowded into the city of Naples—a population without fuel, water, or light; a terror-stricken population crowded together in air raid shelters; a population covered with lice. And lice carry that dreaded disease typhus.
It was the month of October in the year 1943; and that month the hospitals of Naples received 25 typhus cases. To all who know that dreaded disease, this was an ominous sign, for throughout all the years of history whenever typhus had broken out at the beginning of winter, it had never been brought under control until the warmer weather of March or April had arrived. When typhus cases increased to 40 a day in December and to 60 a day in January, and people were dying in the gutters of Naples, it was evident to all that a full-scale epidemic had arrived, and that by February unless something drastic could be done 500 people a day would be coming down with this disease of uncleanliness.
The American soldiers had been vaccinated against typhus, but it was impossible to vaccinate the entire population of Naples. Realizing the seriousness of the situation, Brigadier General Leon Fox, Field Director of the American Typhus Commission in Cairo, flew to Naples to see what he could do. General Fox knew about the magic new wonder killer DDT and how it had protected our troops against lice during the invasion of Africa. He decided to use it in an experiment of tremendous magnitude. In the month of January alone, 1,300,000 people in Naples were dusted with DDT powder, and as more refugees entered the city they were immediately given this treatment. The typhus epidemic passed as rapidly as it had started. By the middle of February it was completely under control. This was the first time on record that a typhus epidemic had been stopped in mid-winter; and for the first time in history that scourge of war—typhus—had been licked. (return)
At times the insect hordes get the upper hand, and millions of human beings drop dead from the poison injected into their bodies by mosquitoes, lice, fleas, or ticks, while others die through eating food poisoned by the ubiquitous fly as he makes his daily round from the manure pile, the privy, or the garbage can to the kitchen table. But even these deaths, horrible as they may be, are no worse than the millions of other deaths due to famine, caused all too often by the incessant appetite of insects for the same food that man consumes. According to Dr. P. N. Annand of the U. S. Department of Agriculture, destruction of crops by agricultural insects costs United States farmers two billion dollars a year, or as Dr. L. O. Howard puts it, devastation by insects undoes the work of a million men.
At other times, man gains a significant victory over his enemies. He concocts a vaccine to neutralize the effect of an insect's bite; he destroys the breeding grounds of his assailants; or he develops a poison that wipes out the insects faster than they can breed. But the latter is a difficult task, for birth control is certainly not practiced by our tiny foes. Newborn insect children can look forward to becoming parents in a few days or even a few hours; and, although human quintuplets make the headlines throughout the world, an insect mother who produced only five offspring at a time would hang her head in shame at this evidence of her virtual sterility.
We should not attempt to minimize the tragedy of war, for wars are senseless and useless, but from an impersonal point of view we must admit, for the sake of accuracy, that insects have killed many more men and have caused much more human suffering than have all the wars of history. And in addition, mosquitoes, lice, and fleas have decided the outcome of most of men's wars, and have thus played a bigger role in shaping the political history of the world than have all our military men and statesmen. In fact, World War II—thanks to the medical services and DDT—was the only major war of history in which diseases transmitted by insects did not play a decisive role.
In the 6th century, during the reign of Justinian I, the last of the Roman Empires, plague came out of the Orient and struck Constantinople in the year 532. It soon spread to Italy and the rest of Europe, and killed half the population of the Roman Empire. Shortly thereafter the Roman Empire collapsed, and its collapse was due, at least in part, to the widespread changes brought about by the ravages of the plague.
But for widespread destruction, the epidemic known as the Black Death is in a class by itself. Introduced into Constantinople from Asia in the spring of 1347, it quickly spread through Greece and the Mediterranean Islands, reached Sicily in October, passed on to Naples, Genoa, and Marseilles—where four-fifths of the population are reported to have died—and reached Dalmatia before the end of the year. It was well established in southern France, Italy, and Spain early in 1348, reached Paris by June, and was in England and Ireland by the fall of the year. Shortly thereafter Germany and the Netherlands felt the attack, and by the year 1350 this pestilence had spread throughout all of Europe, even to the distant islands of Iceland and Greenland.
When the cold, clammy fingers of the Black Death touched a community, few inhabitants escaped. In many towns and cities, more than half the population died. The total number of deaths throughout Europe is hard to believe. At last 25,000,000 people—one-fourth of the population of Europe were killed by this visitation of the plague, and some authorities place the total deaths as high as three-fourths of the whole population.
But even this destruction of human life did not satisfy the demon of the plague, for it returned again and again to many parts of Europe over the next thirty years. In many regions, one-third of the population was wiped out in 1359 and 1360; and many Polish towns lost one-half of their populations in 1360 and 1361. Ten years later, in 1370, Russia was revisited by a severe wave of plague that killed 80,000 people in Lubeck alone.
During the next two or three centuries, plague epidemics broke out every once in a while, and although they were not as severe as the Black Death itself, they would all be classified as major calamities if they were to occur in 20th century America. For example, it has been estimated that in Paris alone bubonic plague killed 50,000 in 1418, 40,000 in 1450, and another 40,000 in 1467. Other cities fared just as badly: there were 16,000 plague deaths in Florence in 1418; 40,000 in Constance in 1438; 30,000 in Venice in 1477 and 1478, and 18,000 in Vienna; while in Brussels, in 1502, as many as 500 a day lost their lives.Except for minor, localized epidemics, plague was relatively unknown from the 16th century to the year 1871, when it broke out in the Chinese province of Yunan-Fu and soon spread to surrounding areas. By 1894, when it reached Hong Kong, it was a serious epidemic, and when it arrived in India it killed six million inhabitants of that country in a period of ten years.
From India the plague spread to the sea ports of all the continents of the world, and the United States had its first taste of this disease in 1900 when it reached San Francisco. The United States' epidemic of plague spread fear throughout a population that was well aware of what had happened in other parts of the world when plague became established; but the worst fears were not justified. The total number of recorded deaths was only 314, most of which were reported from California although eight other states contributed to the total. Undoubtedly, the number of unreported plague deaths was much greater than the number reported, but even if we allow for these, this epidemic was a far cry from the Black Death of 14th century Europe. Nevertheless, everyone breathed a sigh of relief when, in 1904, there were indications that this outbreak of plague had died out.
Unfortunately, the United States did not get off as easily as it seemed at the time. Plague is here to stay; and some day, if we are not careful, the black, distorted features of victims of bubonic plague may become commonplace in the cities of America. We will explain this a little more fully later, but first we should tell you how this disease is spread.
It had often been observed even in ancient days, that large numbers of rats died during epidemics of human plague. But the role of the rat in the transmission of plague was not discovered until the present century. The disease itself is caused by a specific bacillus, first discovered in 1894 during the plague epidemic in Hong Kong. It was later demonstrated that plague is primarily a disease of rodents, particularly rats; and in 1906 the British Indian Plague Commission proved that the bacillus is transmitted from rats to man by the bite of the flea.
Actually there are two forms of the disease: the true bubonic plague, which one gets when he is bitten by a plague-carrying insect; and the pneumonic plague, in which the bacillus is carried directly from one person to another by means of infected droplets. But, since the pneumonic form is merely an outgrowth of the bubonic form of the disease, as long as there are rats to act as a reservoir for plague and as long as there are fleas to carry the plague to man, the possibility of tragic epidemics will always be with us. (The common, cuddly, prairie dog is a known carrier, but its admiring public has no fear of bubonic plague.) (return)
It is probable that most epidemics of human plague started when fleas from plague-infested wild rats transferred their place of abode to house rats, and the fleas from the house rats, upon the death of their hosts, jumped over to people. Yet, there is evidence that the rat flea is not the only culprit. Cat and dog fleas, fleas on wild and domesticated birds, and even bedbugs and lice may, under some conditions, play a part in the spread of the disease.
And that brings us back to the San Francisco epidemic of 1900. This epidemic, as was mentioned before, had run its course by 1904, at least as far as anyone then knew. But only on the surface. Among the hordes of rats it was still smoldering, and worse yet, it had spread from the rats to other rodents—ground squirrels, rabbits, chipmunks, prairie dogs, etc.—as was discovered in 1906. Since then, plague has been found in wild rodents in all of the western states, and in many parts of the east. So far, only a few cases a year of human plague have been reported, and in all cases the victims were campers, hunters, and children who came in contact with the wild rodents. But now that the war is over and more and more people are vacationing in the wide-open spaces, will the number of plague cases increase? Or will fleas from the infected wild rodents carry the disease to our city rats and then to the human population? Will plague sweep this country as it did Europe in the 14th century? We don't know the answers yet. But if the worst does come, we will have only ourselves to blame. Unlike the inhabitants of medieval Europe, we know how plague is spread. We can't pass it off as an act of God. We know that we must beware of the flea. He's an ugly looking beast, and his bite is worse than his appearance.
As was the case with bubonic plague, hundreds of years elapsed before man found out how typhus was spread. It was not until 1909, when Charles Nicolle discovered that typhus is transmitted from man to man by lice, that the mystery was stripped from this disease and men learned that there was more to body cleanliness than merely the elimination of body odor. People who change to clean clothing once a week won't harbor body lice, and if these individuals take a bath before putting on their fresh garments, so much the better. But only a small percentage of the world's population can boast of a standard of living so high that it permits of a change of garments and a bath tub. When people are crowded together in concentration camps or in city slums, when homeless, underfed refugees drag their weary bodies through the rubble of bombed-out cities, lice move in to feed on the anemic blood of the unhappy individuals.
Since typhus is transmitted by lice, it is easy to understand why waves of typhus have devastated Europe and Asia for hundreds of years. The first bath tub was introduced into America in about 1840, and for years thereafter many prominent medical men of the day wrote learned tracts and made impassioned speeches about the dangers of bathing. The Saturday-night bath did not become an American tradition until many years later, and even then many reactionaries continued to resist this revolutionary idea.(return) Imagine what conditions must have been like in Europe in, say, the 15th, 16th, or 17th century? Practically no one bathed, and everyone, from the poorest peasant in his filthy rags to the proudest queen with her equally filthy petticoats, was infested with crawling, biting vermin.
Typhus is one of the numerous fever-producing diseases caused by germs that are intermediate in size between the bacteria and the filterable viruses. This class of organisms is called the Rickettsiae, after their discoverer, Howard Taylor Ricketts, an American who, ironically, contracted typhus and died in 1910 in Mexico City while he was studying tabardillo, the Mexican form of the disease.
Because the symptoms of typhus are similar to those of a number of related diseases, it is impossible for the medical historian to estimate when typhus first began to change the history of the world. Many of the epidemics described by early writers might have been typhus, but the evidence is too incomplete for a proper diagnosis. We do know, however, that typhus broke out among the army of Ferdinand and Isabella during the siege of Granada in 1489-1490, and that 17,000 soldiers are supposed to have lost their lives from the disease many more than were killed by the weapons of the Moors.
And in 1528, typhus decided the fate of Europe by entering into the battle between Charles V and Francis I for control of Italy. In 1527, the Imperial Army of Charles V marched through Italy, sacked Rome, and made a prisoner of the Pope, Clement VII, who was allied with Francis I of France. Then plague broke out in the city and killed a large proportion of the population as well as the soldiers of the Imperial Army. Even the Imperial General, Lannoy, died of the disease. The army of Francis I was not long in coming, and the decimated Imperial troops were in no condition to put up a fight. The remnants of the once-proud Imperial army managed to get to Naples where they fortified the city, and here they were besieged by the French Army under Lautrec. The surrounded army was dying of starvation and was ready to give up when typhus suddenly struck the French army of 25,000 men and reduced it within 30 days to about 4,000 survivors, at least according to some accounts. Lautrec was forced to retreat, Clement VII and Charles V patched up their differences, and, in 1530, Charles V was crowned ruler of the German Empire.
And yet, to show the impartiality of typhus, Charles V was forced to abandon the siege of Metz in 1552, when his armies were stricken with a typhus epidemic and 30,000 men died from disease.
A number of other outbreaks of typhus occurred during the remaining years of the 16th century, usually when armies were on the march—and then came the Thirty Years' War, from 1618 to 1648. Few periods of history held so much suffering for so many people. It was not the battle casualties alone, or even the atrocities perpetrated upon helpless civilian populations by conquering soldiers-—nd these defy all description. It was pestilences of all types, and in particular, plague and typhus, marching side by side with the armies, that accounted for the majority of the deaths and decided the outcome of many of the battles. The 60,000 deaths in Lyons and the 25,000 in Limoges in 1628 are merely examples of what took place all over Europe.
Skipping the pages of history to another decisive war, the campaign of Napoleon against Russia in 1812, we again find the louse of greater importance than the generals. Everyone has read of the dreadful suffering of Napoleon's troops when they retreated from Moscow—how men froze to death by the thousands and died of starvation. Of an army of over half a million men at the beginning of the campaign, Napoleon returned to Paris with only a handful. About 300,000 men perished from disease alone—about about twice as many as died from battle wounds—and of these typhus accounted for a large proportion, although dysentery and pneumonia killed no small number.
When most of us think of the Crimean war, that took place in 1854-1856, we think of either Florence Nightingale or the "Charge of the Light Brigade." But instead of shedding too many tears over the "noble 600," let's pay our respects to the more than 100,000 who died from disease. It is impossible to say how many of these deaths were due to typhus and how many to cholera and dysentery, but reliable accounts inform us that there were two violent typhus epidemics during the war, and that they struck the opposing armies with about equal intensity.
In World War I, there were also two severe typhus epidemics, and future historians may record the fact that both played important parts in shaping the history of the world from the year 1914 on. The first outbreak occurred in Serbia in November of 1914. It started among the Austrian prisoners whom the Serbians had captured, and soon spread throughout the Serbian Army and the civilian population. In less than six months over 150,000 people had died, and Serbia was practically helpless. The Austrian Army could easily have gone through Serbia and attacked Turkey, Bulgaria, and Greece before these countries could have put up an effective resistance. But fear of typhus held them back, and the Central Powers lost their initial advantage.
Typhus flourished among the Eastern armies throughout the war, but vigorous delousing programs kept it pretty well under control among the Germans and Austrians. However, after the retreat of the Russian armies in 1916, typhus cases in Russia began to increase in number, and a full-scale epidemic, like those that had devastated Europe in the Middle Ages, was on its way. The spread of the disease was accelerated by the chaotic conditions of civil war; and between the years 1917 and 1921 there were 25,000,000 victims of typhus in the Soviet Republic, and from 21/2 to 3 million of the victims died.
Because World War II passed without a major typhus epidemic, we might be inclined to assume an attitude of complacency and delude ourselves into believing that "it can't happen here!" That would be unfortunate, for there are dark clouds on the horizon. Typhus is not unknown in this country. Although there have been no epidemics of the classical European type, there have been occasional localized outbreaks of the disease. Since the typhus-infected louse can live for not over 12 days, it seemed highly improbable to students of typhus that these sporadic attacks were due to transmission of the disease from man to man by lice. They decided to investigate; and their investigations showed that typhus can be carried by household rats—and probably by other rodents—and that it is transmitted from rat to rat by rat fleas and rat lice. Of course, when a flea carrying the deadly Rickettsiae bites a human, the disease can become established in man, and if the victim is lousy, he can in turn pass the disease on to those with whom he comes in contact. Thus, the rat is not only the carrier of plague he is also a reservoir of typhus. And keeping our bodies free from lice is not sufficient assurance that we will not get typhus. We must also look out for the flea.
Malaria is not a disease, like bubonic plague or typhus, that kills a high percentage of those that it attacks, but it saps the strength of its victims and makes them miserable for a long, long time. Yet, even though malaria does not kill most of its victims, so many people throughout the world contract this lingering disease each year that the small percentage who die from it comprise a by-no-means insignificant total. Reliable figures are impossible to obtain, but available evidence indicates that at least 3,000,000 of the world's inhabitants die from malaria each year, and probably a hundred times that number are made ill. How many malaria victims die not from the disease itself but from other infections which gain a foothold in their malaria-weakened bodies is anybody's guess, but the total must be at least as great as the number killed directly by the disease.
That malaria has played an important part in the history of the world is beyond question. After the campaign of the Greeks against the Egyptians in 456 B.C., the soldiers of Hannibal brought back malaria, and ever since, the Mediterranean basin has been a favorite breeding ground for germ carrying mosquitoes, waiting to pass on the disease to those who dare enter their domain. The mosquitoes lost no time in spreading malaria among the Greeks in those long-passed days. Before long, the population was so weakened by germs in their blood cells that Greek civilization was on the down grade, and the Greeks were in no condition to withstand the arms of the Roman legions.
The movement of armies has always been a big factor in the spread of malaria, as the Crusaders, the troops of Napoleon, and the British Tommies all found out. In our own Civil War, over 50 percent of the white troops and over 80 percent of the negro troops fell victims to malaria each year; and our Spanish-American soldiers found malaria a more formidable enemy than the Spaniards. Incidentally, when the malaria-infected troops returned from the latter war, our native mosquitoes took advantage of the opportunity to spread malaria among the civilian population. And it is highly probable that malaria victims among the veterans of World War II have been the unwitting sources of recent localized malaria epidemics in the United States.
The name malaria is derived from twos words: mal, meaning bad, and air. Thus the literal meaning of the word is bad air. Long before the role of the mosquito in the transmission of the disease had been discovered, men knew that in some way the air in the vicinity of swamps and other wet places was dangerous. They believed, of course, that evil spirits emanated from the swamps and entered their bodies, causing the chills and fevers, and weakness. This theory was almost correct. But unfortunately, no one realized that the evil spirits had wings and a death-dealing bite. Yet the idea of a relationship between swamps and malaria was quite correct, for water is essential for the breeding of mosquitoes during the larval stage they are aquatic insects.
Since mosquitoes require water, we would except to find malaria along the shores of the oceans, in river valleys, around lakes and swamps, and in damp jungles—that is, unless the winters are too cold to permit mosquitoes to survive. Inhabitants of Asia—particularly of China and India-Mexico, Central America, South America, and the southeastern part of the United States have all had to learn to live with malaria. The use of screens on windows, the draining of swamps, the application of oil and insecticides to breeding places of mosquitoes have helped in some localities, but all of these efforts have been insignificant compared to the benefits conferred by a medicinal agent—quinine extracted from the bark of the cinchona tree.
Whether cinchona bark was first used by the South American Indians or whether the Jesuits deserve credit for discovering its magical properties is of no importance. But since about the year 1630, the bark itself, or quinine, the active principal extracted from the bark, has alleviated the sufferings of untold millions. Today, when armies move into malaria-ridden districts, everyone is given his daily dose of quinine or the synthetic atebrin, and we all thrill to stories of jungle explorers calmly taking quinine pills while fighting wild animals and poisonous snakes. Quinine is not the perfect answer to malaria control. In fact, it is probably incorrect to say that quinine "cures" the disease. If one takes quinine regularly before he enters a malaria-infested district, and if he keeps up the treatment while he is there, the chances are that he will not get the disease but he can't be sure, for some individuals become infected in spite of quinine prophylaxis. After one has contracted malaria, quinine treatment will lessen the severity of the disease, but it will not eradicate it.
The story of quinine is very much like that of rubber. For over two hundred years after cinchona bark was first used in the treatment of malaria, the world had to depend entirely for its supply on the wild trees of South America. Then the situation changed. Sir Clements Markham went to South America with an expedition in 1860 and procured over 400 cinchona plants and a number of seeds, with which he started plantations in India. And two years later a Dutch expedition under a botanist by the name of Hasskarl managed to get out of South America with about 500 cinchona plants and a number of seeds. Two plants survived the journey to Java where they were planted, along with the seeds, to start the cinchona industry in the Netherlands Indies.
The yield of quinine from the original plantings was very low, but in 1865 seeds of a high-yield variety were brought from South America by Charles Ledger, who turned them over to the Dutch when the British Government refused to accept them. With these seeds, the cinchona industry was established in Java on a large scale, and that country was supplying 95 percent of the world's quinine requirements when the Japs moved in, in 1942. The reason for the quinine shortage during World War II is, therefore, obvious.
Although malaria has been with the world for a few thousand years, it is more of a problem today than ever before. With airplanes covering thousands of miles in a comparatively few hours, malaria can easily spread to regions where it was formerly unknown. Infected mosquitoes can ride the airways and live to start an epidemic half way around the world from where they were born. Or, a person may pick up the infection in one country and not become sick until he is back home. All we can do is try to keep the mosquitoes under control. We can't hope to kill all the mosquitoes over millions of square miles of jungles, but we should do our best to keep down their numbers around our cities and towns.
This event occurred in 1900, when Major Walter Reed, of the Army Medical Service, was checking up on the idea that yellow fever was carried by mosquitoes. Major Reed asked for volunteers who would be willing to let mosquitoes bite them, and 26 soldiers and doctors were selected for the role of human "guinea pigs." Jesse Lazear died within a short time others contracted the disease but had uneventful recoveries, and still others, like Pvt. John R. Kissinger, whose obituary we have referred to, lived on in pain and suffering for years. In 1906, the infection in his blood paralyzed Kissinger from the waist down, and thus he remained for 40 years. It is interesting to note that this man, who did so much for others, never looked upon himself as a hero. He refused all offers of money except the $125 a month disabled veteran's pension. How different his attitude was from that of some of the so-called "heroes" of the recent war, whose only combat experience was what they could purchase with a candy bar, and yet who feel that for their contributions to international relationships they should be supported by a grateful government for the rest of their lives.
Yellow fever probably originated in Africa, where there is a large endemic yellow-fever area extending 3,000 miles eastward from the west coast to the upper Nile. From here apparently it was carried to the New World on the slave ships along with their suffering human cargo. The Spanish colonies reported yellow fever as early as 1648, and in the years since then it has taken many lives in lands around the Caribbean. In 1801, Napoleon sent General Leclere with 25,000 men to Haiti to put down the revolt of the negroes led by Toussaint l'Ouverture. The ill-equipped negroes were no match for the French troops and were easily defeated and driven into the interior. But then, yellow fever broke out, 22,000 Frenchmen died, and the 3,000 survivors evacuated the island in 1803. Thus, the Republic of Haiti was born, thanks to the mosquito!
The United States has not been free from yellow fever, although this disease, unlike malaria, has never become established here. Sailing ships from the West Indies often brought yellow fever into North American ports, particularly in colonial days. Cities as far north as Portland, Maine, have had yellow fever epidemics. In 1793, an epidemic killed 10 percent of the population of Philadelphia, and the disease returned six years later. A severe epidemic swept Memphis, Charleston, and Galveston in 1878, and in 1905 New Orleans felt the fury of a sudden attack.
During the Spanish-American War, our troops in Cuba encountered yellow fever as well as malaria, and at that time the cause of the disease was unknown. Because of the seriousness of the disease, something had to be done, and the Yellow Fever Commission was organized to track down the unknown killer. As was related previously, Walter Reed and his co-workers proved—but not until after the war was over—that the Aedes aegypti mosquito was the offender. This information came in very handy later when the Army engineers set to work to build a canal across the Isthmus of Panama. The French had made earlier attempts to build a canal there, but had to give up their efforts when yellow fever got in its deadly work. To the Americans, it was obvious that the first task was the elimination of the mosquito by draining swamps and covering other bodies of water with oil, this was accomplished, and the Panama Canal was built.
Yellow fever is by no means as widespread as malaria, and the yellow fever mosquito is much easier to control than his malaria-carrying relative. The first frost kills Aedes aegypti; therefore, the disease can only become established in climates where it is warm all-year round. The breeding habits of the insects also make control relatively easy. These mosquitoes are very sociable: they like to live near man. Instead of preferring to breed in out-of-the-way swamps or lakes, they breed in cisterns, water-barrels, flower vases, and other small bodies of water around the house or barn. Thus, just by seeing to it that there is no stagnant water—unless it is covered with oil—around the premises, we can eliminate this mosquito.
When a study of the breeding habits of the yellow fever mosquito showed that the insect could be readily controlled, many people began to envisage a yellow fever-free world. The success at Panama and the fact that yellow fever was eliminated from Cuba within a year after the discovery that the disease was transmitted by mosquitoes were certainly reasons for supporting this belief. And when yellow fever was eliminated from Rio de Janeiro and other places, everyone was convinced that with proper efforts success could be achieved within a very short time
But dreams of a yellow fever-free world proved to be as futile as dreams of a world free from war. If every yellow fever mosquito within miles of human habitation were killed, if not a single human being on earth had the disease, it would still not be enough. The disease is not the exclusive property of man—it is shared by monkeys and possibly other animals. The jungles of the world act as huge reservoirs of the disease, and if at any time we relax our vigilance, Yellow Jack might slink out of the jungles and renew his deadly march.Animals, Insects, and Man
Everyone with a dog, a cat, a flock of chickens, or a herd of cows knows that animals, as well as humans, get sick. But we are inclined to overlook the fact that animals may suffer from the same diseases that affect us. Since the infectious nature of disease was first established, we have often fallen into the trap of believing that we could always prevent the spread of a disease by keeping the sick out of contact with the well. But what good does that do if the disease is not spread by personal contact but by means of an insect? And worse yet, what if the insects don't carry the disease directly from person to person but, instead, transfer it from some animal to a human? Maybe your pet dog is carrying a disease that will some day be transferred to you. Don't say that's impossible because your dog is in the best of health. Remember Typhoid Mary and all the other typhoid carriers who show no symptoms of the disease yet can pass it on ink deadly form to others.
Our knowledge of plague, typhus, malaria, and yellow fever should be enough to convince us beyond doubt that our animal population constitutes a reservoir of disease of appalling proportions. But that is only part of the story. How many other diseases come to us over the animal-insect-man bridge? That's hard to say! For some diseases, the chain of events has been proved; for others it is suspected; and for still others, although there is as yet no evidence of an animal origin, the possibility is by no means remote. How else can we account for the fact that some diseases flare up in different parts of the country at about the same time or within a very short time? To attribute this to human carriers doesn't seem logical, for often remote localities that haven't encountered an outsider in months are no safer than populous cities to which visitors come every day from all parts of the country. And why is it that many diseases flourish only in the summertime and subside with the return of cold weather? Logic tells us that the relationship between warm weather, insects, and certain diseases is more than a mere coincidence.In the summer of 1946, a poliomyelitis epidemic swept the country—the worst epidemic since 1916. A disease of unknown origin was again on the rampage. Although the total number of deaths from polio is not large compared to the deaths from other diseases, the mysterious nature of this pestilence plus the fact that it leaves many of its victims cripples for the rest of their lives, make it probably the most dreaded disease in America today. In the case of polio it is difficult, indeed, to attribute the spread of the disease to direct transmission of the virus from one person to another. Since polio and flies flourish at the same time, many students of the disease have suspected that flies are the transmitting agents. There is no direct evidence of this as yet, but the virus of polio has been found in flies, and the disease has been transmitted from flies to experimental animals. But this still leaves the question of where the disease lurks during the winter months. Is it possible that animals, or perhaps birds, harbor the disease in an unrecognizable form, and that flies pick up the virus from the stools of these carriers and transport it to the food of prospective victims? Is the fly responsible for the spread of the various dysenteries that masquerade under the quaint name of "intestinal flu"? It's possible! After all, the fly is known to transmit the disease of pink eye in cattle.
But let's look at a few diseases that are no longer in the realm of speculation. Rocky Mountain spotted fever is a disease very much like typhus. It attacks hunters, campers, and lumberjacks people who go out into the woods and fields. The organism of this disease, like that of typhus, belongs to the Rickettsiae family. In fact, it was Ricketts himself who proved that the bite of the wood tick was the means by which men contracted the disease. But what animal was the reservoir of the disease? Ricketts' death at the age of 39 brought to an end his brilliant investigations, but many others took up the challenge, and during the past 40 years many thousands of wild animals have been examined in attempts to determine the culprit. One man who has trailed the elusive killer for the past 25 years is William L. Jellison of the U. S. Public Health Service. Jellison's investigations indicate that the probable host is a rabbit, Nuttall's cottontail and perhaps some related species.
But don't get the idea that spotted fever is limited to the Rocky Mountain region. This disease, or modified forms of it, has claimed victims in at least 41 of our states, and it has been spreading even to the cities. The summer of 1946 brought an attack of an eastern form of spotted fever to the Borough of Queens in New York, where, during a period of three months, 36 persons, ranging in age from three months to 72 years, contracted the disease. Undoubtedly, ticks spread the disease. But did the ticks get it from an innocent looking cottontail, or did they pick it up from some other rodent, or perhaps a domesticated animal?
Worse than polio in its mortality is encephalitis—literally inflammation of the brain. This disease is world-wide in its spread. A severe epidemic broke out in Vienna in 1916, spread over Europe, reached Great Britain, hopped the ocean to North America, and appeared in about half of the states of the U. S. A. by May, 1920. Australia had epidemics in 1917-1918 and again in 1922 and 1926. In the summer of 1934, 60% of the over 7,000 victims in Japan died, and another epidemic broke out in Japan in the following year. The United States had a widespread epidemic in 1933, and has had a number of localized epidemics since. And the disease is not limited to man, for horses and sheep are also susceptible.
For many years, the mosquito has been suspected of being the transmitting agent, and this was recently proved by Doctors W. H. Hammon and W. C. Reeves of the Hooper Foundation for Medical Research, University of California. Of the many thousands of different kinds of insects that these men and their co-workers collected, only the mosquito was found guilty of carrying the virus. And even more startling was the proof that birds, both wild and domesticated, are the reservoirs of the disease. That is why most cases of encephalitis occur in rural areas, small towns, and suburbs of large cities places where people keep chickens.
We could go on and on and show the possible animal-insect-man relationship in the transmission of many other diseases, but we shall bring this section to a close with a few words about African sleeping sickness. This disease is carried by the tsetse fly, and it affects animals as well as man. The only way to control the spread of the disease is to eliminate the flies, or at least to confine them to areas far from human habitation. That is why a news item from Pretoria, South Africa, dated July 21, 1946, is of particular interest. Briefly, this article stated that the biggest wild animal hunt in the history of Africa would begin the next day. All wild gam—warthog, buffalo, and zebra—over an area of 400 square miles of Zululand were to be rounded up and transported to a specially prepared reserve. And a strip two miles wide was to be laid waste around the reserve on the assumption that the tsetse cannot fly that distance. That is a drastic procedure!
But what are we in this country going to do? Will we be forced to exterminate the wild animals of our woods, or confine them in special reserves? Will the raising of chickens be restricted to certain regions of the country, and the area be placed under strict quarantine? Will it be considered a criminal offense to keep a dog or cat or perhaps a rabbit? Will horse racing finally be barred, not because of the evils of gambling, but because horses carry disease? There are legitimate arguments for doing all of these things. But wouldn't it be much simpler if we would just concentrate on getting rid of the insects that carry the diseases from animals to man? And remember this: don't be misled by the assumption that "it's just a harmless insect." How do you know it's harmless? Just because there is as yet no proof that a particular insect is harmful does not mean that it is harmless. When a man is brought into a court of law, we assume that he is innocent unless he is proved guilty. This is a sensible attitude for it does give greater protection to innocent people, even though, unfortunately, it also permits many of our gangsters and other public enemies to escape punishment for their crimes. But, be this as it may, when we deal with insects, the only wise thing to do is to assume that they are guilty unless they are proved innocent.