It is understandable that people in New England, the Middle Atlantic states, and the upper Midwest live in fear of contracting Lyme disease, but many use it as an excuse to stay out of the woods. Press reports of the disease have people believing that ticks are much more abundant than they once were, and that Lyme disease is spread by ticks carried by deer. This belief has resulted in calls to dramatically reduce deer populations in different areas of the Northeast. Black-legged ticks are sometimes called deer ticks, though Ostfeld claims that deer are not such important carriers as rodents are.
Ostfeld found that when deer are reduced by hunting or excluded by fencing, disease rates actually increase over the next few years. That’s because deer are highly unlikely to transmit a spirochete infection to feeding ticks; they are good hosts for ticks but not for the disease. Small mammals are much better at handing off infections to ticks. Thus deer protect people from Lyme disease by being lousy hosts for Lyme-bearing ticks, “so taking away deer, at least initially, removes the protective role they play in reducing tick infections,” said Ostfeld.
He told me that ecologists tend to be excluded from the pool of rapid emergency funding, and are often left out of the first-response teams when new diseases appear. Also, it seems that money is more available for what Ostfeld explained as “the disease of the month.” Funding for SARS and West Nile peaked in the year or two after the worst disease outbreaks. “Ironically it is the study of those well-established diseases that give us a good grip on how disease systems work. We shouldn’t abandon these intensive studies. They are the gold mine from which we get an understanding of basic disease processes,” said Ostfeld.
In the course of Ostfeld’s studies, he has learned a number of things about Lyme disease. He knows that taking a walk in a fragmented forest, one split up by roads and development, is more dangerous than taking a walk in extensive virgin forest. And he knows that the more opossums, squirrels, and foxes there are in a forest, the less chance there is of catching Lyme—and he suspects that the same is true for the presence of hawks, owls, and weasels. He is focusing now on determining the reasons for these observations, a major part of his studies.
As we’ve said, forest fragmentation enhances the spread of disease. Fragmentation occurs when large, continuous forests are divided into smaller pieces, either by roads, agriculture, urbanization, or other human development—shrinking the area available to animals and plants that rely on the habitat. Some critters, like predators and large-bodied animals, need large areas to maintain viable populations. Some are poor dispersers for whom the strip mall or suburban development is a severe barrier. The results are species losses. The species that are most resilient to fragmentation—mice, chipmunks, etc.—are often the only ones that remain. And these are the bad guys when it comes to disease transmission.
Ostfeld told me that if the tick we found on the mouse earlier that day had bit me, my chances of catching Lyme disease would have been at least 40 percent, but if we’d found the tick in a vacant woodlot in the nearby town of Poughkeepsie, my chances would be closer to 70 or 80 percent. A woodlot is an example of fragmentation, and the town of Poughkeepsie has lots of that.
To test Ostfeld’s theory that fragmented forests increase disease, he and a number of biologists selected fourteen forest fragments that were similar in types of vegetation but were isolated from other suitable habitat for Lyme hosts. What they found was that the larger the forest patch, the smaller the proportion of black-legged ticks infected by the disease it contained.
In the Midwest, tracts of trees in the middle of corn and soybean act like islands in the middle of the ocean. Corn and soybeans play the part of the ocean, since they are sufficiently inhospitable to native animals and create a barrier to dispersal much like the ocean would to an island animal. Thus corn and soybean crops deter many larger forest animals, but small mammals like mice and chipmunks do just fine there. Wooded lots have fewer species altogether, but the animals they do have are the disease amplifiers. Ostfeld found that the larger the size of the wooded tract, the smaller the proportion of diseased black-legged ticks there. But in smaller lots the numbers of infected ticks are astronomical.
The idea that peaceful patches of forest amid cornfields could be harbingers of disease is ominous, but so is the fact that the antibiotics we’ve been counting on to treat those diseases may not be able to help us for much longer.
THE RISE OF SUPERBUGS
Antibiotic resistance is growing so fast that we may soon have nothing left to tackle the new diseases we are fostering. The failure of our medicines is due to farmers who use antibiotics in animal feed to fight off diseases promoted by overcrowded conditions in confined-animal feeding operations for pigs, chickens, and cattle. These practices are creating superbugs that are immune to the antibiotics they’ve already adapted to.
Resistance to antibiotics normally occurs if your doctor prescribes a dosage that is not sufficient to eliminate the disease, or if you don’t take the full number of doses prescribed. In the process, the disease gets stronger and is less affected by the medication on subsequent usage. Bacteria that survive the first treatment multiply and are resistant to the next treatment.
But antibiotic resistance can also come from eating meat from animals once treated by antibiotics. Disease is a particular problem in confined feeding operations where animals are kept in close quarters and fattened up for market. Putting antibiotics into animal feed is meant to lessen the threat of disease and to promote animal growth, but some scientists are finding that part of our increased resistance to antibiotics comes from eating animal products tainted by antibiotics.
Feeding our cattle, chickens, and pigs low doses of antibiotics is a setup for our own resistance to the medicine. In reality, low-dose medication that is not monitored selects for resistant strains of bacteria even in the food we eat. They are the ones that survive, reproduce, and grow stronger.
Antibiotic-resistant bacteria can spread into the air from confined-animal feeding operations that use antibiotics to compensate for the overcrowded conditions in their pens, affecting nearby residents. The resistant bacteria in animals’ manure can wash downstream and enter waterways where people swim and play. Scientists have even found in the sand on Florida beaches resistant bacteria brought there by seagulls.
The FDA recently announced new regulations to urge drug companies and agribusinesses to phase out the use of certain antibiotics in livestock and poultry, but the regulations are voluntary. And according to Ostfeld, this will definitely not end antibiotic resistance. There are large numbers of antibiotics used for livestock that will not be regulated, and so microbes will continue to evolve antibiotic resistance.
But the resistance issues generated by farm animals are not our only worry. The Cary Institute aquatic ecologist Emma J. Rosi-Marshall has studied how antimicrobial chemicals used in personal-care products leak into the environment. Rosi-Marshall claims that putting antibiotics into toothpaste and hand cleaners serves no health purpose—they’re no better than antibiotic-free toothpaste or soap and water—yet they increase antibiotic resistance in the environment.
Common afflictions like gonorrhea have developed resistance to many common antibiotics, including penicillin and tetracycline. Gonorrhea is transmitted sexually between humans. The World Health Organization reports that the disease is becoming a major health challenge in Australia, France, Japan, Norway, Sweden, and the UK due to antibiotic resistance that developed in the late 1990s and early 2000s. Left untreated, gonorrhea can cause painful infections of the reproductive organs, infertility, an increased risk of catching HIV, stillbirths, spontaneous abortions, and blindness in newborns.
Another ailment currently resurging is tuberculosis (TB), a potentially fatal lung disease that has also grown resistant to antibiotics. The bacteria that cause tuberculosis are spread from person to person through tiny droplets released into the air via coughs and sneezes, though you are most likely to get the disease from someone yo
u live with. It was once rare in developed countries, but the number of TB cases has increased worldwide since the 1980s. Part of the problem was caused by the emergence of HIV, the virus that causes AIDS. HIV weakens a person’s immune system so it can’t fight TB germs.
People who have tuberculosis often must take a variety of medications for long periods to get rid of the infection and deal with drug resistance. Various strains of tuberculosis have been found resistant to medications generally used to treat the disease. Multidrug-resistant tuberculosis rampages through the Russian prison system, where prisoners easily catch the disease and spread it to other inmates. The TB bacterium has developed immunity to many drugs, and has begun to proliferate among homeless people and AIDS patients.
The effects of drug resistance are serious and global. An estimated 630,000 people are presently ill with multidrug-resistant tuberculosis. Some 88 million people are infected with gonorrhea, which is also multidrug-resistant. There are 448 million new cases of curable sexually transmitted diseases (STDs)—including syphilis, chlamydia, and trichomoniasis—every year, and health authorities are watching those diseases for the development of resistant strains.
Should drug resistance and a host of new diseases brought on by the elimination of species concern us? How might a major pandemic occur? The influenza epidemic of 1918–19 killed 50 million. The Hong Kong flu of 1968–69 took about one million. The AIDS epidemic has taken some 30 million people so far. It is still a virulent killer in Africa, where the chief victims are now heterosexuals. WHO reports that malaria caused 627,000 deaths in 2012. Right now tuberculosis is making a big comeback.
Michael Greger looks at bird flu as earth’s next big catastrophe. Over the better part of the last two decades a killer strain of avian influenza has devastated birds in Asia, Europe, the Middle East, and Africa. It kills more than half of all its avian victims, and some strains kill even more. And it’s a virus. It can spread through coughing or sneezing, through the air, just as H1N1 or any of our common viruses can.
In rare instances where bird flu has spread from poultry to people, it’s been one of the deadliest viruses ever described. About 600 people have been infected with bird flu and 350 have died, about 60 percent. “But what if the virus were to mutate into easy human-to-human transmissibility?” asked Greger in a televised interview with Thom Hartmann about his book Bird Flu: A Virus of Our Own Hatching. “It would be like crossing one of the most deadly diseases, Ebola, with the most contagious disease ever known, influenza.”
In 1900, the leading causes of death were tuberculosis, pneumonia, and enteritis. Today, more than a century later, the chief causes of death are heart disease, cancer, and stroke. These chronic diseases have overtaken infectious diseases as our number one killers. This is not a bad thing, since chronic diseases generally affect older populations. Thus the abatement of infectious disease in just the last century has increased average life spans by thirty years or more. The decrease in the role of infectious killers is largely due to inoculations and antibiotics. Some of the greatest recipients of these benefits have been the young, who are disproportionately affected by infectious disease.
But the balance is changing. Recently, Dr. Margaret Chan, director general of the World Health Organization, addressed a group of experts gathered in Geneva, Switzerland, to tackle antibiotic resistance. “Some microorganisms are resistant to nearly everything we can offer to save the lives of infected patients,” Chan said in a speech to the convention. “And few new antimicrobials are in the R&D pipeline. Medicines lost because of microbial resistance are not being replaced. We are moving towards a post-antibiotic era where common infections will once again kill. If we lose our most effective antimicrobials [antibiotics, antifungals, antivirals, and antiparasitics], we lose modern medicine as we know it.”
Disease is not likely to take man out, any more than the plague, World World II, or AIDS has. But if you take new diseases, couple them with antibiotic resistance, add some rising populations, and mix in a lack of food and proper nutrition, then we might have the recipe for our own extinction.
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WARNING SIGN III: SQUID AND SPERM WHALES
UNLIKE THE EMERGING THREAT of new diseases and the resistance to antibiotics, one doesn’t have to wait to see how man’s interference is changing the marine environment. Many of those changes are already here. One shining example is the Gulf of California between mainland Mexico and the Baja California peninsula, what was once lovingly referred to as the “Baja Fish Trap” for its abundance of marine life. Overfishing, acidification, and warming waters have altered the ecology of these famous marine waters. The marlin, swordfish, and sharks that anglers once came here for have dramatically dwindled and a new ecology made up of Humboldt squid and sperm whales has taken over.
It is still a pristine environment. A drive south of the US border down Mexico’s Highway 1 takes you past volcanoes, mountains, and sculpted red rock through a series of valleys populated with whiplike boojum trees and giant cardon cacti. About five hundred miles south of the border it summits the coastal mountains and descends rapidly onto the Gulf of California just above the historic French mining town of Santa Rosalía. The Gulf of California, in Mexico, was created six to ten million years ago when Baja California began to separate from mainland Mexico, producing the geologically diverse peninsula and the biologically diverse waters of the Gulf.
On a recent visit, the moist evening breeze brought in the briny smell of marine life to cool the town of Santa Rosalía as the fishermen headed toward the dock and the boats for the nighttime catch. Biologist William Gilly, from Stanford University’s Hopkins Marine Station—a big, friendly academic with lots of interesting stories—and his group of student researchers joined the fishermen as they motored out to sea. It was September on the Baja Peninsula, where open-ocean schools of tuna, swordfish, and sharks were once an annual gift of the Gulf, but have diminished in recent years.
Now Santa Rosalía fishermen pursue Humboldt squid (also known as jumbo squid), which appear to have replaced many of the finfish in the Gulf of California. They still fish as before, only they go out in the late evening, not at dawn. At sunset, I watched the local fishermen join the parade of pangas, twenty-two-foot open skiffs with outboard motors that departed from the sandy shores. The Gulf waters turned from blue to black as the boats lined up about a mile offshore, their colored lights glistening in the evening shadows. The fishermen used hand lines baited with fluorescent jigs to catch the squid.
These boats represent a growing group of local small-scale fishermen who, but for their outboard motors, rely little on the hardware of the modern commercial fishing industry. Instead, they fish the waters off the Baja Peninsula from unregulated camps that line the shore using primitive gear. Over the last decade the Mexican Humboldt squid fishery has caught between 50,000 and 200,000 tons of squid annually, mostly from the Gulf of California, and sold it predominantly to markets in Korea and China.
The Humboldt squid was named for the Humboldt Current, an ocean current that flows north along the west coast of South America from the southern tip of Chile to northern Peru. It was thought that the Humboldt squid in Baja originated in Pacific waters off South America, though when, exactly, they arrived off Baja is a mystery. There have been few historical sightings of the squid in marine records farther north than the Galápagos Islands off South America.
Humboldt squid (Docidicus gigas) have not only invaded the waters of the Gulf of California, they have expanded their domain northward along the Pacific coast as far as Alaska and westward along the equator toward the Hawaiian Islands.
Squid here seem to have filled a niche left vacant when finfish such as tuna, sharks, marlin, and swordfish began to disappear in the late twentieth century. Squid have a much shorter life span than other fish, rarely living over a year and a half. And they are highly productive, meaning they can bounce back from fishing pressure much faster than finfish, which are not as productive. But Gilly thought t
his factor was less important than the ability of squid to cope with the spread of low-oxygen waters, a new problem on the horizon that may be giving the squid their ticket to expand.
The increase in the biomass of Humboldt squid in the Gulf of California is promoted by the development of low-oxygen zones in the water, a result of climate change and possibly decreased ocean circulation. These zones are different from the dead zones created by agricultural runoff, but the two could act in tandem to worsen the effects. Low-oxygen waters support fewer species but can support high quantities of those few species that are tolerant of it. Again, we are seeing the live-fast-die-young generation: a few species that are able to survive a toxic environment, which then take over the world—or the ocean in this case.
Santa Rosalía developed as a copper mining town in the late 1800s, and it was prosperous until the ore ran out in the 1920s. Still there are touches of prosperity from its mining days. Gustave Eiffel, of Eiffel Tower fame, built the church in the town center in France and then shipped it to this Baja town, where it was reassembled in 1897, an indication of the wealth mining generates. Still the town has none of the lights, bars, or tourist trappings you might find in Puerto Vallarta or Acapulco farther south.
The Santa Rosalía copper mine has recently reemerged as newer techniques have made the mining of old ore deposits viable. Gilly wonders what the long-term effects will be as the mine gears up for another run. Only, the proportions are much larger now than in the late 1900s, as miners will be using huge equipment to extract lower amounts of copper from already-mined soils.
Gilly has developed a program for monitoring intertidal shellfish communities, both near the new mine and in a more protected area about twenty miles north of town. “If the mine begins to disturb the marine environment off Santa Rosalía, the monitoring plan is designed to detect it. We’re lucky to be able to commence monitoring before major production commences,” said Gilly. He’s working with students from a local technology school that was established here in recent years.
The Next Species: The Future of Evolution in the Aftermath of Man Page 11