Seven Modern Plagues

and How We Are Causing Them

Mark Jerome Walters

• Publisher: Island Press
• Year: 2014
• ISBN:
  9781610914666
• Topic: Biowissenschaften
• Subtopic: Wissenschaft Allgemein

Epidemiologists are braced for the big one: the strain of flu that rivals the pandemic of 1918-1919, which killed at least 20 million people worldwide. In recent years, we have experienced scares with a host of new influenza viruses: bird flu, swine flu, Spanish flu, Hong Kong flu, H5N1, and most recently, H5N7. While these diseases appear to emerge from thin air, in fact, human activity is driving them. And the problem is not just flu, but a series of rapidly evolving and dangerous modern plagues.
According to veterinarian and journalist Mark Walters, we are contributing to-if not overtly causing-some of the scariest epidemics of our time. Through human stories and cutting-edge science, Walters explores the origins of seven diseases: mad cow disease, HIV/AIDS, Salmonella DT104, Lyme disease, hantavirus, West Nile, and new strains of flu. He shows that they originate from manipulation of the environment, from emitting carbon and clear-cutting forests to feeding naturally herbivorous cows "recycled animal protein."Since Walters first drew attention to these "ecodemics" in 2003 with the publication of Six Modern Plagues, much has been learned about how they developed. In this new, fully updated edition, the author presents research that precisely pinpoints the origins of HIV, confirms the link between forest fragmentation and increased risk of Lyme disease, and expands knowledge of the ecology of West Nile virus.He also explores developments in emerging diseases, including a new chapter on flu, examining the first influenza pandemic since the Hong Kong flu of 1968; a new tick-borne infection in the Mid-West; a second novel bird flu in China; and yet a new SARS-like virus in the Middle East.Readers will not only learn how these diseases emerged but the conditions that make future pandemics more likely. This knowledge is critical in order to prevent the next modern plague.

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The Dark Side of Progress: Mad Cow Disease

1.

Near the village of Midhurst, West Sussex, an hour’s journey south from London through green glens and soft hills, stands a seventeenth-century brick-and-timber farmhouse surrounded by purple hydrangeas and lipstick-red geraniums that tilt in the breeze. The lichen-covered clay tile roof and weathered walls seem to have grown from the earth itself. Sprays of red and yellow flowers spill from every corner of the grounds, and wild roses climb a trellis above a gate leading down to lush pasture and an ancient stone stable. It is as if Pitsham Farm were drawn from the enchanted poetry of William Wordsworth, where “majestic herds of cattle, free / To ruminate, couched on the grassy lea.” Or so it might have seemed until, three days before Christmas in 1984, one of Peter Stent’s cows began acting strangely.

“At first we dismissed her as a cow with a bad disposition, kicking in the milking parlor and all that,” Stent told me. But when she got worse, Stent called his veterinarian, David Bee, who visited the farm. The cow hunched her back, leading Bee to believe she might have a painful kidney ailment. More cows soon fell ill, and Bee returned several times to attempt to diagnose the ailments. The first cow grew worse, developing head tremors and an unsteady gait. In February 1985 she died. The mysterious illness continued to spread through the herd. At a loss for a diagnosis, Bee dubbed the affliction “Pitsham Farm syndrome.” Whatever the root of this malady, Bee concluded that it was attacking the brain, and he and Stent decided to ship a sick cow to the local agriculture ministry.

“I shall never forget that cow,” Stent said. “The man came with a trailer already loaded with two sheep on their way to slaughter. When we prodded the cow into the trailer, she saw the sheep; then she went berserk and killed them. I thought she was going to destroy the whole trailer. She was extremely violent.” Unfortunately, when the cow arrived at the local ministry she was killed with a gunshot to the head, which destroyed the brain and rendered it useless for analysis.

Determined to find the cause, Stent and Bee loaded up cow number 142—the tenth cow to be afflicted with the illness—and had her driven to the ministry. The head was removed intact and sent to the Central Veterinary Laboratory in Weybridge, Surrey, where the brain could be examined by a pathologist.

A stocky man with gentle blue-gray eyes, Stent sat in a lawn chair at a table and paused to sip his tea. A row of royal purple foxgloves nodded in an early summer breeze from the English Channel, twenty miles away. “Spooky behavior for these kindly animals,” he recalled. “I cared about them and hated to see them sent to slaughter.”

Stent’s wife, Diana, appeared in the sunny yard and refilled our cups. A wood thrush sang three platinum notes followed by a reedy tremolo from a bush near an abandoned brick privy. Stent separated his right hand from his teacup long enough to make a short, sweeping gesture. “It’s becoming more difficult to make a living from the farm anymore. I’m fortunate indeed to have other means. The price of milk has gone so low that we can’t compete with larger operations. Now, with the Channel Tunnel open, tanker trucks bigger than my milking parlor bring cheap milk from the continent. We have 600 beef cattle, but people’s feelings have really changed about eating meat.”

Eager to give his respected veterinarian a place in our conversation, Stent called Bee on his cell phone to arrange a meeting. We drove the backroads of the 600-acre farm past mostly empty pastures. When we arrived at the dilapidated milking parlor, Stent leaned out the car window and pointed inside the building’s wide doorway. “I couldn’t justify modernizing the operation in light of things. Now, look in there. Those are the old feed bins. At the time, I couldn’t imagine what my cows were being fed. It’s in there we first noticed the cows acting strangely. That’s the spot where BSE began as far as the history books are concerned,” he said, using the initials for bovine spongiform encephalopathy, the technical name for mad cow disease.

Bee’s clinic was in the village of Liss, a twenty-minute drive. “As if BSE weren’t enough, the foot-and-mouth epidemic last year finished off a lot of farms,” Stent said as we drove along. He was referring to another highly contagious cattle disease that had recently swept through the United Kingdom. Although not dangerous to humans, it is one of the most contagious and economically devastating livestock diseases. “We didn’t get foot-and-mouth at Pitsham, but we were quarantined like farms throughout the UK. Any farm with the disease, all the animals were burned.”

Bee greeted us in the waiting room of his clinic and ushered us into a treatment room so we could talk without interruption. A man in his late forties or early fifties, he wore wire-rimmed glasses, and his eyes shone with inquisitiveness. “Still haunts me sometimes,” he said, recalling his first encounters. “You’d never recognize it in an undisturbed grazing herd. Then I’d walk up to the fence and suddenly a cow two hundred yards away would lift its head and fix its gaze on me with an eerie hypervigilance. ‘That cow’s infected,’ I’d say to myself. If you stressed it, its symptoms could explode into kicking, tremors, aggression, a wobbly gait. An infected cow would come apart at the seams. Really spooky.”

The task of examining cow 142’s brain fell to Carol Richardson, a pathologist at the Surrey laboratory. She noted a strange sponge-like appearance strikingly similar to what is found in sheep with a well-known neurological disease called scrapie. Richardson wrote “spongiform encephalopathy” on the necropsy form and left the slide for Gerald Wells, her supervisor, to examine. Wells confirmed Richardson’s diagnosis and filed the slide.

A year later, a cow from Kent developed similar symptoms; it became clear that the disease was not limited to Stent’s farm. When this cow’s brain reached Wells’s laboratory, he discovered that it also had a spongiform encephalopathy. In 1987, fourteen months after Richardson’s diagnosis of cow 142, Wells hailed his own discovery of “a novel progressive spongiform encephalopathy in cattle” and published a paper on his finding without so much as mentioning Richardson’s diagnosis of the cow from Pitsham Farm—the first-ever documented case of mad cow disease.

Prior to Wells’s 1987 publication, several cows at a farm in Malmesbury, Wiltshire, seventy-five miles east of Pitsham Farm, had also developed a fear of walking over concrete or venturing around corners. Some hung their heads low as if exhausted. Others developed a high-stepping gait in their back legs as if walking on hot pavement. Milk production dropped. Cows fell down and couldn’t get up. The epidemic soon affected fourteen counties in southern England.

Although mad cow disease was apparently a new affliction, it belonged to a class of known brain-wasting diseases called TSEs, or transmissible spongiform encephalopathies. The name indicates that the diseases can be contagious and lend a spongy appearance to the brain, just as in the cow’s brain Richardson had described. The first human TSE, Creutzfeldt-Jakob disease (CJD), was described in the 1920s. This degenerative disease leaves its victims, in the early stages, with loss of memory, unsteady gait, muscle spasms, and jerky, trembling hand movements. Another TSE, scrapie in sheep and goats, was scientifically described in 1936, although one of its symptoms—violent scratching to the point of mutilation—had been known for centuries. About a decade later, a TSE was identified in ranch-reared minks.

In 1957 yet another human TSE, kuru, was identified in Papua New Guinea. Then, in 1967, chronic wasting disease was identified in some deer and elk in the western United States. BSE was officially added to the list of TSEs in 1987 with the publication of Wells’s paper. But mad cow disease was not just another TSE: never before had the affliction expressed itself in such a widespread outbreak. By 1988 more than 2,000 cows had been stricken, and in 1992 alone more than 35,000 cases of BSE in cattle would be reported. By January 1993 almost 1,000 new cases in cows were being reported every week. “Incurable Disease Wiping Out Dairy Cows” proclaimed a headline in London’s Sunday Telegraph in 1987: “A mystery brain disease is killing Britain’s dairy cows, and vets have no cure.” Farmers began to fear for their livelihoods and their rural traditions. But at least they were not fearing for their own lives—not yet.

2.

In October 1989 a report surfaced describing a woman, believed to be at least thirty-six years old, who had been diagnosed with Creutzfeldt-Jakob disease. That disease struck, according to one study, fewer than one in every 10 million people in Britain and Wales each year, and its usual victims were middle-aged or older people; the average age of victims at the onset of the disease was fifty-seven. CJD in the young—a teenager, for example—is so rare as to typically occur only once every twenty or thirty years. Conventional wisdom held that CJD was either inherited or contracted from contaminated surgical instruments, transplants, or cadaver-derived growth hormones once used to treat dwarfism. When it was learned that the young woman had been associated with a farm where mad cow disease was present, people began to wonder whether she had contracted her disease from an infected cow. This was dismissed by a government scientific committee, however, which concluded that “the risk of Bovine Spongiform Encephalopathy to humans is remote.”

In August 1992 came the case of Peter Warhurst, a sixty-one-year-old dairy farmer at Meadowdew Farm in Simister, north of Manchester, who died of Creutzfeldt-Jakob disease. Warhurst had culled a “mad cow” from his herd three years before. The prestigious British medical journal Lancet described this as “the first report of CJD in an individual with direct occupational contact with a case of BSE.” The report said that the case was probably a chance occurrence but raised “the possibility of a causal link.” It was not a link the government wanted to hear about. Livestock is a mainstay of the United Kingdom’s economy, and the stakes were huge.

Kevin Taylor, the government’s assistant chief veterinary officer responsible for BSE control, publicly dismissed the notion of a link between mad cow disease and CJD, saying, “I don’t think that a link between this case and BSE is even conjectural.” This echoed repeated claims by British agriculture minister John Gummer that there was “no evidence anywhere in the world of BSE passing from animals to humans” and that “on the basis of all scientific evidence available, eating beef is safe.” At a boat show in Ipswich in 1989, Gummer had vouched for the safety of beef, this time in a BBC television report that showed him helping his four-year-old daughter, Cordelia, chomp down on a beef burger nearly the size of her face. “When you’ve got the clear support of the scientists who deal with these matters [and] the clear action of the government, there is no need for people to be worried,” he proclaimed, “and I can say completely honestly that I shall go on eating beef and my children will go on eating beef because there is no need to be worried.”

But new cases kept emerging. In May 1993, Duncan Templeman, a sixty-four-year-old Somerset dairy farmer, came down with CJD. There had been three cases of BSE on his farm, and he was a beef-eater. Eight months later, in January 1994, a third dairy farmer, from Just, in Cornwall—some of whose cows had also contracted BSE—entered a hospital with loss of memory and slurred speech. The fifty-four-year-old farmer soon became mute, and he died of pneumonia some months later. The Lancet, which reported the case, concluded that “the occurrence of CJD in another dairy farmer . . . is clearly a matter of concern.” Although the report emphasized that the farmer might have contracted the disease from his cows, the government’s Spongiform Encephalopathy Advisory Committee emphasized that he might not have done so and the case therefore did not require “the Government to revise the measures already taken to safeguard public health against occupational and other possible routes of exposure to the BSE agent.” But one member of the committee warned that should a fourth case arise, the tide of probability would turn: farmers were probably catching CJD from their cows. In September 1995, a fourth ill farmer came to light. As if that weren’t convincing enough, a rash of puzzling CJD cases had begun to occur in beef-eating young people not associated with farms.

In 1993 fifteen-year-old Victoria Rimmer of Connah’s Quay, Deeside, came down with CJD—the youngest reported victim in Great Britain in almost twenty-five years. Victoria had been exceptionally healthy until May 1993, when she began losing weight, developed trouble with her vision, and soon became apathetic. A brain biopsy revealed spongiform encephalopathy. Her condition deteriorated. She had fits, her body twitched uncontrollably, and she went blind. According to her mother, the British newspaper Today reported, beef burger was Vickie’s favorite food. Kenneth Calman, England’s chief medical officer, countered, “No one knows what illness she is suffering from . . . there is no evidence whatever that BSE causes CJD.” Victoria soon fell into a coma that lasted four and a half years, ending in her death.

The notion that CJD might be linked to a person’s diet was not new, and the supporting evidence was as tantalizing as it was scant. In 1984 the American Journal of Medicine reported four cases in which individuals who commonly ate animal brains—those of wild goats, squirrels, and pigs—came down with CJD. The authors concluded: “Our case, along with experimental evidence for oral transmission of Creutzfeldt-Jakob disease and other spongiform agents, support[s] the hypothesis that ingestion of the infective agent may be one natural mode of acquisition of Creutzfeldt-­Jakob disease.”

After the identification of mad cow disease, not surprisingly, such speculation increased. In 1997 a neurologist at the University of Kentucky came across a CJD patient in Florida, a native of Kentucky who had a long history of eating squirrel brains back home—not an uncommon practice in rural parts of the state, where the brains are sometimes scrambled with eggs or put in a meat and vegetable stew called burgoo. The neurologist later discovered that all five patients of a neurology clinic in western Kentucky who were suspected of having CJD had a history of eating squirrel brains. The patients were not related, and they all lived in different towns, facts that minimized heredity or direct contact as a means of transmission. The study was widely reported in the media but criticized in the scientific community; for one thing, squirrels apparently don’t get spongiform encephalopathy.

In 1998 the Lancet reported the intriguing case of a sixty-year-old man from Italy who had been admitted to the hospital with muscle contractions, an unsteady gait, visual difficulties, and problems speaking. Two weeks after admission, he became mute and couldn’t swallow, and several months later he died. The man, as far as anyone knew, had no unusual eating habits. But about the same time he was admitted to the hospital, his seven-year-old cat developed uncontrollable twitches and episodes of frenzy and hypersensitivity to touch. The cat grew progressively worse and soon was unable to walk. There was no evidence that the cat, which slept on the owner’s bed, had ever bitten him. Analysis of cells from the man’s and the cat’s brains showed remarkably similar abnormalities. Either the man caught CJD from his cat, the cat caught it from the man, both were infected by a common source, coincidence led them to become infected independently, or the cases were simply misdiagnosed.

Epidemiologists rightly caution that for every victim of CJD who had eaten the brain of a wild animal, there were thousands of other people who had eaten the same thing without contracting the disease. Such is the slippery nature of anecdotal evidence. But it is also worth noting that of the thousands of people who may have eaten BSE-infected beef, only a select few contracted the human form of mad cow disease.

By the end of 1995, ten suspected cases had been documented in young people in the United Kingdom. Senior government officials continued to insist there was no link with beef. Even as official denials flew, several prominent scientists, including some government advisors, were preparing a paper for the Lancet that would confirm people’s worst fears—that the bovine disease and the human disease were connected—by acknowledging the “possibility that [these cases were] causally linked to BSE.” Not until just before the study’s publication in the April 6, 1996, issue did the British secretary of state for health, Stephen Dorrell, admit to the House of Lords that the ten young people probably were suffering from what had become known as variant CJD, the human form of mad cow disease. Researchers soon added physical evidence to the statistical case: the agent of mad cow disease in humans was indistinguishable from the agent that caused BSE.

Mad cow disease seemed like medical science fiction. One of humankind’s most ubiquitous domesticated companions, the dairy cow, widely known for its gentle nature, and a frequent subject of poetry and painting, had delivered a ferocious new disease unto its keepers. No one could say how the cows had gotten it, but speculation soon shifted to their pastured brethren the sheep. It was one more connection in a strange set of circumstances that seemed to link sheep, cows, and humans in a bizarre and unprecedented web of affliction.

3.

Scrapie, the illness of sheep and goats that can cause the animals to madly scratch themselves raw, was first clinically recognized in Great Britain in 1732. An early description from Germany describes how suffering animals “lie down, bite at their feet and legs, rub their back against posts, fail to thrive, stop feeding, and finally bec...