by Amy Stewart
FLEAS
These tiny, bloodsucking carriers of bubonic plague have also been used as an agent of war. During World War II, Japan’s biological warfare project, called Unit 731, developed a method for dropping bombs filled with plague-infected fleas into enemy territory. They tested it in Ningbo, a seaside town in eastern China, and Changde, a city on the Yuan River in Hunan Province. Both communities experienced outbreaks of plague as a result of those experiments.
An estimated two hundred thousand Chinese people died at the hands of Japan’s biological agent program. An operation called “Cherry Blossoms at Night” would have released the fleas over California, but that plan was never executed. The Japanese military also conducted horrific medical experiments on prisoners, subjecting them to gas chambers, disease, frostbite, and surgery without anesthetic. Although evidence of these war crimes did come to light after the war ended, the United States granted immunity to doctors involved with the project in exchange for access to their research and data. As part of the agreement, the project was kept a secret. It was not until the mid-1990s that historians began to report upon the atrocities committed by Unit 731.
He was branded an enemy and thrown into the bug pit. There he suffered the attacks of assassin bugs, who were kept alive in between prisoners with gifts of fresh meat.
PAINFUL
Bed Bug
CIMEX LECTULARIUS
In Toronto, a sixty-year-old man went to his doctor complaining of fatigue. He was diabetic, a recovering alcoholic with only a year’s sobriety, and a former crack cocaine user, so fatigue was the least of his problems. But the doctor found severe anemia, which he treated with a prescription dose of iron. A month later the man was back with even worse symptoms, requiring a blood transfusion before he could return home. A few weeks later, he needed another transfusion. The blood loss was inexplicable and frightening.
SIZE:
4–5 mm
FAMILY:
Cimicidae
HABITAT:
Nests, caves, and other warm, dry places near food sources
DISTRIBUTION:
Temperate regions throughout the world
Then the doctor paid a call to his patient at home. The problem was immediately apparent: bed bugs were everywhere. He could even see them crawling on the man during the visit. The public health department was called in; after the apartment was sprayed with insecticide and the old furniture removed, the man gradually recovered.
The bed bug travels at night, lurking in low light, feeling its way toward warmth and the tantalizing odor of carbon dioxide. It approaches its dinner — that is, you — with outstretched antennae, gripping the skin tightly with tiny claws. Once it has a good grip, it begins rocking back and forth, working needlelike feeding organs called stylets into the skin. It bites gently, piercing the skin just enough to get the blood flowing. The stylets probe around under the skin in search of a good-sized blood vessel to tap into. The bed bug’s saliva contains an anticoagulant to prevent clotting, so it can settle down and feed. If it is left alone to enjoy its meal, it will feed for about five minutes and then wander off. But if you were to swat at the bug in your sleep, it would probably move a short distance away and bite again, leading to a telltale series of three sequential puncture wounds. Dermatologists call these bites “breakfast, lunch, and dinner.”
Dermatologists call bed bug bites “breakfast, lunch, and dinner.”
Before World War II, bed bugs were a fact of life in the United States and around the world. Pesticides developed around that time helped eliminate them, but now the blood-sucking parasite is back. Reasons for its reappearance include an increase in international travel, a reduction in the use of broad-spectrum pesticides in favor of targeted baits, and, alarmingly, the bed bugs’ own resistance to chemical controls. Researchers at the University of Massachusetts have reported that bed bugs in New York City show new mutations in nerve cells that allow them to survive exposure to neurotoxic ingredients in bug sprays. In particular, they found that pyrethroid sprays, the synthetic version of a natural insecticide derived from chrysanthemum flowers, had little effect on New York bed bugs, while a population collected in Florida was easily wiped out by the poisons.
What has this meant for the average New Yorker? Although bed bugs have not been shown to transmit disease, the bites can cause allergic reactions, swelling, rashes, and secondary infections from scratching. The blood loss from an infestation can be severe enough to cause anemia, particularly in children and people in poor health. The sleep loss and emotional distress alone are enough to bring on serious psychological problems.
A bed bug can survive up to a year without feeding. In the wild it might live in a nest or cave alongside its prey; in the city it prefers upholstery, loose wallpaper, or the dry, dark spaces behind pictures or inside light sockets. The worst outbreaks may be accompanied by streaks of feces along the tufts of upholstery. A strange sweet odor that comes from the bug’s scent glands pervades homes with large populations of the bugs. The compounds it produces, hexanol and octenol, are used to communicate with other bed bugs, but the smell is a giveaway that trained dogs can detect even when people can’t. It’s been described as smelling like coriander — and in fact the name coriander comes from the word koris, which is Greek for bug. For the most part, the bugs don’t travel around with people, although homeless people who don’t change clothes often may find that bed bugs follow them everywhere, laying eggs inside clothing or even under overgrown toenails.
Controlling bed bugs is not easy, especially in apartment buildings, where they can move from one room to another via ductwork or cracks in the plaster. City dwellers are starting to avoid purchasing used furniture for fear of unwanted hitchhikers, and mattress companies have learned the hard way that using the same truck to haul away old mattresses and deliver new ones can perpetuate the very infestations that people are trying to eliminate.
One promising new control is an old-fashioned desiccant dust, messy but nontoxic, mixed with the bugs’ own pheromones. This so-called alarm pheromone entices them to get up and move around, exposing them to enough of the desiccant to cause them to simply dry up and die. An even more natural form of pest control may show up all by itself: the house centipede, Scutigera coleoptrata, feeds on bed bugs, as does the so-called masked hunter, Reduvius personatus, an assassin bug that gets its blood meal by robbing bed bugs of theirs.
Meet the Relatives The Cimicidae family includes not only bed bugs, but bat bugs and bird bugs as well; all depend on the blood of their prey for survival.
PAINFUL
Biting Midge
CULICOIDES SPP.
One midge is an entomological curiosity, a thousand can be hell!” So said Queensland scientist D. S. Kettle. He should know: the biting midge is such a serious pest in that part of Australia that it actually depresses property values. A 2006 study estimated that this tiny, blood-sucking annoyance was responsible for driving down real-estate prices to the tune of $25 to $50 million in the desirable Hervey Bay area, where new homes built close to man-grove swamps were plagued by the insects.
SIZE:
1–3 mm
FAMILY:
Ceratopogonidae
HABITAT:
Near beaches, lakes, bogs, and other damp areas; most active in humid, warm regions
DISTRIBUTION:
Primarily North and South America, Australia, and Europe, but also elsewhere throughout the world.
The midges posed such a problem that angry homeowners marched on city hall, demanding a solution, and there were even threats of violence against local officials. Soon a Biting Midge Investigative Committee was formed to combat the menace. According to a community report, “the strain of living with biting midge even caused marriages to break up,” presumably because couples were forced to spend more time indoors together rather than enjoying the respite of an afternoon on the golf course. The community developed a program of insecticide spraying that was effective against the midg
es and mosquitoes, met the requirements of Australia’s environmental agencies, and seemed to mollify the angry locals.
The midge, which is more commonly called a no-see-um in the United States, is a tiny black fly that likes to congregate around beaches and lakes, making it a serious irritant for vacationers. (Midges are sometimes called sand flies, but the sand fly is actually quite a different insect.)
“One midge is an entomological curiosity, a thousand can be hell!”
Biting midges are known as pool feeders. They like to break the skin and simply lap up the blood that seeps out, rather than go to all the work of hunting for a blood vessel. Their bites can cause an allergic reaction that leads to unsightly swollen red bite marks. This reaction is sometimes called sweet itch or, in Australia, Queensland itch. Only the females bite, but the males swarm people constantly, waiting for the females to show up for dinner, giving victims the impression of being constantly under attack.
Campers, beach lovers, and golfers on the Gulf and Atlantic coasts have long suffered through attacks of biting midges during the summer months. In Scotland the so-called Highland midge, C. impunctatus, is so aggressive that it deters tourists from hiking or golfing near the country’s famous bogs and lakes during the summer. A local pest control company established the Scottish Midge Forecast to help predict midge infestations based on weather conditions and encourage tourists to plan their trips accordingly.
Although midges are not known to transmit human diseases in the United States, in Brazil and around the Amazon both the midge and the mosquito transmit a dengue-like disease called Oropouche fever, which causes severe flu-like symptoms but usually results in full recovery. In some parts of Brazil, up to 44 percent of the population test positive for antibodies to this virus.
A bite from a midge can also deliver a parasitic nematode from the genus Mansonella; the tiny worms usually inhabit humans undetected, making diagnosis difficult but also making treatment less urgent. Scientists recently discovered that the nematodes require an abundant supply of bacteria in their own guts; after giving patients in one West African village a round of antibiotics, the bacteria inside the nematodes were killed off and the nematodes then died as well. But because the disease is relatively mild, causing only itching, rashes, and fatigue, it seems unlikely that antibiotics will be distributed on a large scale to rid people of the parasite.
The midge poses a more serious threat to cattle around the world, transmitting a disease called bluetongue that causes a severe fever, swelling of the face and mouth, and the characteristic blue tongue. Thanks to the migration of the biting midge, this disease has spread throughout most of the world, and is gradually moving into more northern climates as the midges themselves move north, perhaps due to climate change.
Meet the Relatives Biting midges are true flies; they are related to black flies, mosquitoes, and other tiny bloodsucking pests. There are about four thousand species of midges worldwide.
DANGEROUS
Black Fly
SIMULIUM DAMNOSUM
As recently as the 1970s, a third of villagers living alongside West African rivers could expect to be blind by the time they reached adulthood. Photographs of children leading blind adults around by ropes demonstrated that loss of sight was a normal part of life in these fertile valleys. Eventually those areas had to be abandoned, a terrible decision for people who depended on the rich soil for agriculture. The blame for this tragedy rests with the black fly, called one of “the world’s most persistent and demoralizing man-biting insects” by a leading medical entomologist. But the fly alone is not to blame. The bizarre life cycle of a skinny wormlike creature called Onchocerca volvulus is the real culprit in the horrific disease known as river blindness, or onchocerciasis.
SIZE:
2–5 mm
FAMILY:
Simuliidae
HABITAT:
Near fast-moving streams
DISTRIBUTION:
Various species are found throughout the United States and Canada, as well as across Europe, Russia, and Africa
Female black flies lay their eggs on the surface of fast-moving rivers, where the water has the high oxygen content their young require. The eggs hatch and the larvae linger along the river for a week before they emerge as fully formed adults. The females mate immediately and only once; after that, they desperately seek out a warm-blooded creature to feed upon. It is only by drinking the blood of a person or an animal that they can get enough nutrition to nurture their eggs along. They will live for a month, laying their eggs in the river to perpetuate the cycle. Some rivers can produce one billion flies per kilometer of riverbed in a single day.
Black flies are “determined feeders,” meaning that they anchor themselves and refuse to let go until they are satisfied. A person under attack in an area of heavy infestation might expect to get hundreds of bites in an hour. In some cases the flies swarm so densely, climbing into the ears, nose, eyes, and mouth, that an animal can suffocate or run itself off a cliff in an attempt to get away. The flies have even killed livestock by exsanguination, or the draining of blood. During a massive attack, the shock to the system from the various compounds found in their saliva, a condition called simuliotoxicosis, can also kill an animal in a couple of hours. In 1923, along the Danube River in the southern Carpathian Mountains, a ferocious swarm left twenty-two thousand animals dead.
But the most remarkable fact of the black fly’s short, blood-thirsty life is that if it happens to feast upon the blood of a person infected with a parasitic nematode called Onchocerca volvulus, it takes part in a weirdly intricate cycle of disease transmission.
The young nematodes — called microfilariae during their early larval stage — cannot grow and develop while they are swimming in the bloodstream of a human. They must be sucked into the body of a black fly while it feeds in order to grow into their next larval stage. Once inside the fly, they move into its saliva and wait for it to feed again — because only by moving back into the body of a human can the worm continue its journey to adulthood.
If they successfully navigate this complicated voyage from human to fly and back to human, the microfilariae finally transform into adult nematodes that can reach over a foot in length. These adults nestle into nodules under a person’s skin where they live for up to fifteen years, mating and producing as many as a thousand offspring per day.
In 1923, along the Danube River in the southern Carpathian Mountains, a ferocious swarm left twenty-two thousand animals dead.
And what do those offspring do with their time? Most will never be lucky enough to find their way into the gut of a black fly, as they must do to reach the next developmental stage, which means that they will be doomed to swim around the human body in their juvenile state for a year or two until they die — but not before inflicting terrible symptoms on their host. They burrow into the eyes, where they cause blindness. The skin gets depigmented and breaks out in rashes and lesions. The tiny creatures cause such a horrible itch that people break their skin open with sticks and rocks in a futile attempt to scratch the irritation away. This, in turn, causes bacterial infections, makes it impossible to sleep, and has even driven some poor souls to suicide.
Today 17.7 million people are infected worldwide, primarily in Africa and Latin America. Of those, 270,000 are blind and 500,000 live with severe vision impairment. One approach to controlling the disease is to kill the black fly, and that worked through the 1950s when DDT was available. But the flies became resistant to DDT, and DDT itself accumulated in the food chain at toxic levels. Now a particular strain of a natural bacteria (Bacillus thuringiensis var. israelensis) is used in its place, but this provides no treatment for the millions affected by the disease.
It’s only by drinking blood that black files get enough nutrition to nurture their eggs along.
A dewormer for animals called ivermectin has proven effective against the microfilariae, but not the adults. Its manufacturer, Merck, provides the drug free of charge to pu
blic health groups, who distribute annual treatments to infected people. Once the adult worms die — which can take over a decade — the treatment can stop, but in the meantime, repeated doses are necessary to keep the young worms in check and prevent transmission of the disease. The program, which was first limited to a few countries in Africa, has been so successful that abandoned river valleys are being resettled and distribution of the drug is beginning in other African and Latin American countries.
Meet the Relatives Although there are over seven hundred species of black fly worldwide, only 10 to 20 percent are pests to humans or animals. They don’t all transmit disease, but they are an incredible nuisance, interfering with tourism and outdoor enterprises, like logging and farming, throughout the summer months.
PAINFUL
Black Widow
LATRODECTUS HESPERUS
To whom it may concern,” wrote twenty-six-year-old Stephen Liarsky in his suicide note. “Whenever a man usually takes his life it is always proper to give the reason. My reason is because, first, I have no job. I have no one in this world except a woman I love terribly, and she is too good for me. I am ashamed of myself because I am a failure and not a success. God bless Rose. Good-bye.”
