Japans Fleas And Flies

The scale of 20th-century conflicts led to civilians becoming strategic targets. The morale of a populace, the industrial output of a city, and the agricultural production of a farming district were all vital to protracted, large-scale warfare. The horrific toll on noncombatants from the German Blitzkrieg, Allied bombing, and V-i rocket attacks in the European theater was not lost on the Japanese, who needed no excuse to attack the Chinese populace, but welcomed the implicit acceptance of such tactics by the international community and the opportunity to further test the moral waters.

The Japanese began using poison gas against the Chinese in 1937 as a military tactic that also served as a probe of political sensitivities.1 When compelling evidence of chemical warfare was brought to the League of Nations in 1939, nothing was done. Japan had already resigned from the League to protest the body's condemnation of the Manchurian occupation, and the international community's attention was focused on German aggression in Europe. With the rest of the world turning a blind eye, Japan turned to entomological weapons.

In the summer of 1940, plague broke out in the city of Xinjing following what may have been the first attack using flea-charged Uji bombs.2 However, there is only fragmentary information on the complicity of the Japanese or the scale of suffering. The role of Unit 731 in subsequent disease outbreaks became unambiguous, as Ishii documented that his six-legged soldiers could reliably deliver death with an even more efficient delivery system (see Figure 10.1).

By modifying aerial spraying equipment, the scientists found that aircraft could directly release clouds of fleas over enemy targets. This method was used at Chuhsien, where plague irrupted a month after the attack.3 The outbreak developed more slowly than hoped, but 21 people eventually died

Figure 10.1. The oriental rat flea is one of the insect vectors of bubonic plague, and it was the key to Unit 731's entomological weapons program. This photograph shows a mass of bacteria in the insect's digestive system (the dark mass just in front of its blood-filled gut). This blockage prevents the hungry flea from ingesting a meal and forces the insect to regurgitate bacteria into the host, thereby spreading the pathogen in its futile efforts to feed. (Photo courtesy of CDC)

Figure 10.1. The oriental rat flea is one of the insect vectors of bubonic plague, and it was the key to Unit 731's entomological weapons program. This photograph shows a mass of bacteria in the insect's digestive system (the dark mass just in front of its blood-filled gut). This blockage prevents the hungry flea from ingesting a meal and forces the insect to regurgitate bacteria into the host, thereby spreading the pathogen in its futile efforts to feed. (Photo courtesy of CDC)

and many times that number were afflicted. Such losses were sufficient for sabotage operations, but the High Command would want more bodies in a full-fledged attack. And in short order Unit 731 delivered.

The raid on Quzhou demonstrated the potential of infected fleas to inflict serious and sustained damage.4 The attack in the fall of 1940 triggered an outbreak that continued for the next six years—the city was still losing people after Japan had lost the war. Perhaps some of the death toll was a consequence of the populace being completely unfamiliar with plague. Their first experience with the disease, courtesy of Unit 731, cost 50,000 lives. Entomological warfare was proving to be wickedly effective, but Japan's finest scientists thought they could do better than relying on bloodthirsty parasites.

Believing that technological cleverness could trump evolution, Ishii's staff devised a method for protecting and distributing pathogens without the assistance of vectors.5 They loaded up three planes with granules containing plague bacteria. On contact with water, the pearly-white grains were designed to swell, rupture, and release their lethal payload. Millions of granules rained down over Kinghwa in November 1940—and then the researchers waited and waited . . . and waited. There were no reports of disease in the city. The microbiologists at Unit 731 grudgingly concluded: no fleas, no plague.

The attacks escalated toward wholesale entomological warfare. For example, the stockpile at Hangzhou for an impending raid included 11 pounds of cholera bacilli, 150 pounds of "typhus" (whether this represented pure microbes or infected lice is not clear, but the latter seems likely given the weight of the payload), and 15 million plague-infected fleas.6 As Ishii's confidence grew, he began to allow his minions a greater role.

Ishii entrusted Colonel Ota Kiyoshi with the raid on Changteh.7 To ensure that his master would not be disappointed, the colonel used a bit of overkill. Ota supervised more than a hundred men in producing, loading, and releasing 100 million infected fleas. Within days, an 11-year old girl had died of plague and an outbreak was underway. The disease swept through the city and into the surrounding villages. That first fever-wracked season left 500 dead, and another 7,000 would succumb before the epidemic subsided.

Over the next two years, Unit 731 would attack more than a dozen villages, towns, and cities, causing more than 100,000 casualties. Although the exact number of targets and victims of infected fleas will never be known, some firsthand accounts of the suffering and panic inflicted by entomological warfare have survived.

Archie Crouch, an American missionary, was stationed in Ningbo, a bustling port city with all the requisites of a good target: sultry weather, a thriving colony of wharf rats, and a dense population of humans. Crouch was in the unusual and unfortunate position of being perhaps the only western eyewitness of an entomological raid by the Japanese.8 His diary provides a haunting view of what transpired that fateful day:

October 27, 1940. . . . It was unusual to have an air-raid alarm that late in the day. . . . I heard nothing until the plane was over the city. It was flying very low, and that, too, was unusual, since the bombers usually came in groups of three, six, or nine. As this lone plane circled over the heart of the city a plume of what appeared to be dense smoke billowed out behind the fuselage. I thought it must be on fire, but then the cloud dispersed downward quickly, like rain from a thunder head on a summer day, and the plane flew away.9

Seeking an explanation of what the plane had dropped, Crouch learned that "the gossip around the city that morning was that the plane had dropped a lot of wheat, so much in some streets that the people were sweeping it up for chicken feed." In fact, the payload had included millions of fleas along with a generous portion of sorghum, wheat, and rice. The purpose of the grain was to attract rodents to the drop site, so that the fleas would have plenty of opportunity to find a blood meal.

The full meaning of the strange aerial deposit would become evident to the people of Ningbo. A week after the raid, Crouch wrote:

We would soon learn that fleas carrying bubonic plague can cause more civilian and economic destruction than squadrons of planes carrying bombs . . . when the first bubonic plague symptoms appeared among people who lived in the center of the city.10

The first wave of sickness swept up 20 people, a modest start but sufficient to catalyze an epidemic. Along with the spread of disease came another outbreak, every bit as important to the Japanese goal of economic and industrial disruption—terror. Unless the authorities took decisive action, panicked people would flee the infected zones and spread plague throughout the city and into the countryside. Understanding the gravity of the situation, the Chinese organized a Herculean quarantine program. According to the journal of the duly impressed American missionary:

Armies of brick masons were organized to build a fourteen-foot-high wall around the six square blocks in the center of the city where plague was concentrated. The plan was to burn that section of the city as soon as the wall was completed and the people evacuated. . . . No one who lived in the area enclosed within the wall was allowed to leave except through the decontamination sheds.11

As soon as the evacuation was complete, the Chinese laid trails of sulfur throughout the walled-off area, ignited the powder at strategic points, and watched as "fires from the burning sulfur raced through the maze like sparkling snakes." The people of Ningbo knew that having lost 97 of their neighbors to plague was a virtual victory relative to the scale of suffering that would have taken place without drastic intervention. What they did not know was that some infected rats and fleas survived the conflagration and that plague would return to the city in 1941, 1946, and 1947, with lesser irruptions until 1959. They also could not know why the death rate was so high: the Japanese had used a particularly virulent strain cultured from human subjects. And finally, given the importance of the Confucian concept of reciprocity to the Chinese people, perhaps they suspected—but could not have known—that insects have the capacity for poetic justice.

Handling millions of infected fleas was almost sure to produce accidents, as described by Ishibashi Naokata, a civilian employee of Unit 731:

Once, during a transfer, the fleas got loose and got all over the airport. There was a scare that everyone working in there would become infected, and a lot of commotion followed. We sprayed large quantities of insecticides over the airfield, and because of it extensive areas of grass died and turned a bright red.12

A few losses to "friendly fire" did nothing to alter the path of entomological warfare, which was on a trajectory toward ever more deadly operations (see Figure 10.2).

With the Japanese having lost any qualms about waging war with insect-borne disease, the scale of biological attacks was limited only by military logistics. The attack on the Zhejian region combined conventional troops with microbial and entomological weapons in a massive, coordinated campaign.13 Unit 731 assigned more than 300 men to support the 14,000 Japanese infantry in

Figure 10.2. Wang Binhong was a victim of Unit 731's attack with plague-infected fleas at Congshan, where a third of the 1,200 residents succumbed to the disease. He was sent away from the village to avoid the outbreak, but fell ill shortly after he returned. His father had heard of a man who survived the disease by consuming alcohol, so the 15-year-old boy was fed nothing but alcohol. Wang Binhong survived both the treatment and the disease. (Photo by M. Ziegler)

a retributive and strategic offensive. Colonel Doolittle's audacious bombing raid of Tokyo, Yokohama, and other cities had enraged the Japanese, and they knew that the American pilots had received sanctuary among the villages of Zhejian. The Japanese were seeking both to punish the Chinese and to ensure that the region would not become a host for airfields in support of U.S. bombing runs.

The Japanese troops were ferocious in meting out punishment to the settlements where American airmen had received aid, and Unit 731 was able to drive home the lesson with their special brand of suffering. Infected fleas rained down from the planes, and pathogenic bacteria flowed from barrels and nozzles. Despite these tactics, the Japanese biological campaign was largely ineffectual. While the military leaders were in no mood for philosophizing, the scientists understood that sometimes we learn more from our failures than from our successes. Although outbreaks of plague had laced the region, the use of cholera had been a disaster. Pouring and spraying the bacteria put the attackers at greater risk than the defenders—the Japanese suffered 10,000 biological casualties and 1,700 fatalities, while few Chinese contracted the disease.

Ishii's staff realized that unless a better means of dispersing the bacteria could be found, cholera was a loose cannon. But its potential to devastate an enemy was simply too great to abandon weaponization. Until now, cholera had been viewed as a water-borne disease, so dumping bacteria into wells or spraying microbes over ponds and streams seemed to be sensible tactics. The problems were that handling the concentrate often infected your own troops, that even large volumes of culture were quickly diluted in most water sources, and that the bacteria required some rather particular conditions to survive, let alone flourish, in aquatic systems. There had to be a better way of sparking an epidemic.

The scientists of Unit 731 knew that, once under way, cholera spreads like wildfire. The disease produces a flood of watery diarrhea that is swimming with bacteria. Death from dehydration occurs when a person loses about 15 percent of available body water. This lethal volume works out to be about ten quarts—and with a quart of liquid feces per hour, death from shock, kidney failure, and circulatory collapse may occur in less than half a day. Once the flow of contaminated excrement gains momentum within a human population, the disease proliferates rapidly as victims contaminate the water supply. The problem for the Japanese military was how to get the cycle started.

Merely dumping bacteria into the enemy's water hadn't infected enough people to trigger an outbreak. A new approach was needed—or the adaptation of a tried-and-true tactic. If insects were effective in delivering plague, perhaps these carriers could be conscripted for cholera. From this small leap of entomological logic came the greatest military success in the modern annals of biological warfare.14

Japanese epidemiologists realized that the key to triggering the initial wave of infection was to put high numbers of bacteria in intimate contact with even a relatively small fraction of the target population. What Unit 731 sought was a cholera carrier with a strong affinity for humans.

House flies (Musca domestica) get their name for a very good reason—they flourish among human habitations.15 To be more precise, these insects are what entomologists call "filth flies," for it is not our houses but our garbage and sewage that the adults and maggots find so tasty. With respect to enteric disease transmission, flies acquire pathogenic bacteria while feeding on excrement from infected individuals. Studies have found 4 million bacteria per fly in insects collected from slums, and almost 2 million in flies from apparently clean neighborhoods.16 The hairs on the fly's body function as microbe magnets, while the sponging mouthparts of these insects are peppered with tiny pores and fine hairs ideally suited for picking up pathogens. To make matters even worse, because house flies can consume only fluids, they regurgitate prior to feeding on solid food to initiate the breakdown of their meal. The insect vomits up a soup of enzymes, including a portion of its last snack, onto the prospective meal—a bit of food on a person's plate, cup, hands, or lips. And given the ease with which house flies could be produced en masse, the Japanese had three of the essential ingredients to trigger a cholera epidemic: bacteria, vectors, and people. There was just one problem.

Unfortunately for the Japanese, the Chinese were fastidious, not particularly prone to producing breeding grounds for flies around homes, schools, and factories. Introducing bacteria-laden flies would create an outbreak only if public hygiene could be undermined. Fortunately for the Japanese, war is messy—and with a bit of timing, the consequent filth can be a powerful prelude to entomological warfare. With this final piece in place, the Japanese were ready to launch an attack the likes of which the world had never seen.

Yunnan Province had become a thorn in the side of the Japanese. This region hosted an Allied supply line into China, providing Chiang Kai-shek's Nationalist forces with the supplies and arms they needed to resist the Japanese. The route leading from Burma through the city of Baoshan and into southern China made this tropical region one of the most strategically vital areas in the war. On May 4, 1942, a wave of 54 Japanese bombers descended on Baoshan, dropping tons of explosive and incendiary bombs. The city was decimated:

10,000 people died in the raid and more than three-fourths of the buildings were destroyed. Mixed in with the conventional ordnance were a number of ceramic-shelled bombs.

At first, these bombs appeared to be duds—the casings had burst open without exploding. But the nature of these special devices was soon evident. Lin Yoyue, a retired elementary school teacher, described the bizarre contents as being a "yellow waxy substance [with] many live flies struggling to fly away." He had discovered Unit 731's brainchild, officially called the Yagi bomb, but known among its developers as the "maggot bomb." It was divided into a section packed with a gelatinous slurry of bacteria and a compartment loaded with flies—not larvae, as the device's vile nickname would suggest, but winged adults. On impact, the casing burst and the insects were splattered with a slimy coating of cholera bacteria. Released from their confinement, the flies dispersed into the decimated city. The populace had no chance to ponder the unusual invaders, as the Japanese were not done with their dastardly plan.

The planes returned for three more bombing runs on May 5, 6, and 8. Rather than simply moving the rubble around, these attacks had a purpose unique in the annals of aerial bombardment. The goal was to move the people. Sickening Baoshan was a fine start, but the supply route of the Allies could just be moved to bypass the diseased city. The Japanese sought a regional epidemic, and the series of bombings was intended to drive the infected people into the countryside—carrying cholera along with them. The refugees unwittingly complied, taking along their churning intestines.

By June, cholera had spread into more than half of the counties in Yunnan Province. Villages were ravaged as far as 125 miles from Baoshan, with 25 to 50 percent mortality being typical. Some 60,000 of the city refugees died of the disease, with more than twice this number succumbing throughout the region. The final tally reached 200,000 victims across an area equal to that of Pennsylvania—a scale of death that provided the Japanese with an unqualified victory. The Allies' supply line was utterly contaminated. Moreover, with this epidemic raging, the Chinese Nationalist Army could not base troops in the region. By creating this diseased no-man's-land, the Japanese were free to divert thousands of soldiers to other fronts. Any strategy that worked this well was worth repeating.

In August 1943, the Japanese duplicated their "decimate-and-contaminate" ploy in the northern province of Shandong. Because Japanese troops were in the area, a new twist was added—their soldiers were vaccinated against cholera to prevent losses to "friendly fire." Once again, an epidemic swept through the region afflicting towns and villages and spreading into parts of adjacent provinces.

Cholera's final score from the maggot-bomb campaigns: China 410,000, Japan 0.17 Yunnan and Shandong became the Hiroshima and Nagasaki of China, with flies and microbes taking as many lives as atomic bombs took in Japan.

By now, the frequency and characteristics of disease outbreaks—along with eyewitness accounts of falling fleas and fleeing flies—left no doubt as to Japan's tactics. General Chiang Kai-shek communicated the nature of these attacks to Winston Churchill and Franklin Roosevelt.18 In 1943, Roosevelt threatened to retaliate against the Japanese if entomological raids persisted. The Japanese were undaunted and, more important, they were becoming desperate. Threats of future retribution coming from across the ocean hold little sway when a nation sees an enemy massing in the present, across its border.

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