Bio Invasion

No longer hindered by time and distance, disease can strike any species, anywhere

When reptile dealer Wayne Hill brought an ailing leopard tortoise into the veterinary clinic at the University of Florida at Gainsville in 1997, he was in for a big surprise. His pet, it turned out, had stowaways. Discreetly hidden beneath the animal's "armpits" were thumbnail-size African ticks, Amblyomma marmoreum. These critters can harbor a bacterium that causes heartwater, an animal disease that is endemic in sub-Saharan Africa but has spread to the Caribbean.

In the U.S., where cattle, sheep, deer, and elk have no immunity to the disease, heartwater could wipe out whole herds. Fortunately, the ticks were identified, says Michael J. Burridge, director of the Heartwater Research Project at UF. A quick inspection of Hill's facility revealed that it was crawling with the African ticks--and this was just one of a dozen infestations turned up by Burridge and his colleagues. The ticks proved to be heartwater-positive, raising alarms of a full-blown outbreak. And now worries about heartwater have spread to ranchers. "It could shut us down," says Jim Handley, executive vice-president of the Florida Cattlemen's Assn., who frets about a host of other new animal plagues as well. "West Nile encephalitis, screw worm--they all frighten us," he says "If those things are sneaking by, that's really scary."

And sneaking by they are. The tick that spreads heartwater is just the latest in a long list of foreign diseases that threaten ranch and farm economies throughout the world. These illnesses receive little media attention compared with exotic human afflictions such as Hanta virus or Ebola virus. But biologists say that alien animal and plant pests represent a much broader set of dangers than rare human illnesses do. And it's not either/or: In many cases, the animal plagues are closely associated with human illness as well.

Scientists and environmentalists have dubbed this phenomenon "bioinvasion." And the telltale signs of it are found all over the world. Mad cow disease, which decimated Britain's cattle industry, has now been identified in Belgium, France, Ireland, Switzerland, and Portugal. Even as Britain struggles with this blight, markets are slamming shut to its exports of hogs, which have been hit with an outbreak of classical swine fever. In Asia, Japan and Korea are battling outbreaks of foot-and-mouth disease (FMD) in cattle, which may have slipped in from China. In Mexico, just 200 miles from the Texas border, nearly 14 million chickens were slaughtered this spring because of a highly contagious virus called Exotic Newcastle Disease. A virus called Nepha has destroyed the Malaysian pork industry and killed 105 people. In North America, veterinarians are fighting a deadly parasitic disease called leishmaniasis. Rarely before found on these shores, it has has sickened and killed hundreds of foxhounds in 21 states and Canada.

Experts blame the spread of these and other pests on an explosion in world trade, business travel, and tourism. Global trade policies aggravate the problem by putting strict limits on countries' abilities to ban animal trade. Meanwhile, in the U.S., years of flat budgets for border inspectors and disease researchers have left populations of animals--and humans--doubly exposed.

Such oversights can incur appalling costs. Even in the U.S., which has been spared the worst of the recent plagues, the price tag for battling agricultural blights ran to $9 billion last year, according to a Cornell University study. A serious outbreak of FMD would more than double that figure and ripple straight across the whole farm and food economy. "Our industry is at greater risk than ever of animal disease," says Terry L. Beals, executive director of the Texas Animal Health Commission. The implications are so dire that the National Intelligence Council--the research arm of the CIA--issued a report listing foreign animal diseases as a risk to national security. "We have been extremely fortunate so far," says Ernest W. Zirkle, president of the United States Animal Health Assn. (USAHA). "But everybody says [an outbreak] is a matter of when, and not if."

Public alarm over bioinvasion is most acute where the lines between animal and human risks are blurred. And that happens more frequently than most people realize. Hundreds of common diseases are zoonotic, meaning they affect animals and humans alike. Indeed, scientists estimate that as many as 70% of all pathogens are capable of jumping species.

Leishmaniasis and West Nile virus show why this is so frightening. In the U.S., the former has been detected only in hunting dogs. But in countries such as India, the parasite is endemic--and deadly--in humans as well. West Nile virus, which has killed a total of seven people around the New York metro region, may have entered the country on a smuggled bird or a jet-setting mosquito. It can also be fatal to chickens, pigs, and horses. And since it can be carried by ticks as well as by several species of mosquito, experts say the chances of eradication are slim. If the disease reaches Florida, for example, where the horse industry alone generates some 72,000 jobs, "the socio-economic damage would be immeasurable," says Leroy Coffman, the state's head veterinarian.

STRICKEN. Britain provides a chilling illustration of how economic costs and human suffering become intertwined in animal plagues. Herds of cows were probably first infected with bovine spongiform encephalopathy (BSE), or mad cow disease, in the early 1980s, when they were fed protein supplements that included the ground-up remains of sheep and cows. Some of those remains may have been infected with abnormal "prion" proteins, which proliferate in a live animal's brain, reducing it to sponge-like mush.

Britain has already spent an estimated $6.25 billion to clean up the mess--not including the jobs lost. Beef product exports are still down 99% from 1995, and the economic effects could easily stretch another 15 years. But the greater misery is that the illness seems to have jumped to humans. More than 80 people in Europe have been stricken with the new, human form of this always-fatal disease. As many as 136,000 may eventually become sick, according to an Oxford University study reported in the August issue of Nature.

North America is hardly insulated against such dangers. Animal researchers have long been tracking prion-linked diseases among wild populations of deer and elk. And in Vermont, the Agriculture Dept. recently ordered the destruction of three small flocks of imported sheep that may be carrying a new form of mad cow disease. There is evidence that before being brought into Vermont from Belgium, some of the sheep in the flock might have been exposed to mad cow through a feed supplement. Despite controversy over testing procedures that may have led to false positives, the USDA deemed the risk too great to let the sheep live.

The human errors that led to the BSE outbreak may be atypical in animal plagues. But the involvement of multiple species is hardly unique. The deadly HIV, which causes AIDS, may have originally leapt from monkeys to humans. And all human influenzas originate in birds and beasts, killing an estimated 40,000 a year.

But even where they do not affect human health, animal plagues can cripple whole industries. Japan and Korea are now struggling with FMD--their first outbreaks of the virus in more than 70 years. To date, Korea has had to slaughter 350,000 head of cattle at a cost of $90 million.

That loss pales, however, next to the 3.8 million pigs Taiwan was forced to destroy in a 1997 outbreak of FMD. The disease, thought to come from the mainland, could eventually cost Taiwan as much as $15 billion in lost exports of pork and other products. And the damage goes beyond the loss of revenue potential: After an outbreak, countries risk losing their their place in global markets.

NIGHTMARE. Could a similar event take place in North America? Once again, it's a question of when, not if. Contamination spreads at the speed of transport. And the threat is vastly amplified by soaring agricultural trade, along with ever-greater numbers of world travelers. Since 1995, agricultural imports to the U.S. have risen 28%. And international travel to the U.S. is up 33%, to more than 100 million travelers annually, since 1988.

Most of those visitors make their trips in far less time than it takes diseases to incubate. And it's not just ailing passengers that worry health officials: It's what is in their luggage. Checking for contaminated products and insect stowaways is a logistical nightmare. By some estimates, worldwide customs officials inspect just 5% of all bags. What's more, about 30,000 people cross U.S. borders illegally every week. On top of that, exotic pets such as reptiles provide yet another channel for pathogens and parasites.

Avirus such as FMD is brilliantly adapted to exploit these channels. Notoriously difficult to kill, it can survive for several weeks on clothes and for up to 24 hours in the human respiratory tract. "I can go from a farm in South America to one in Texas in a day," says Alfonso Torres, deputy administrator of the USDA's Veterinary Services Division. That's all the time it takes these days to start an outbreak.

Time and distance, in short, are no longer barriers for this disease. And the potential damages are astronomical. At risk are U.S. agricultural exports--currently worth $50 billion annually and expected to grow to $76 billion by 2009. A 1999 study by the University of California at Davis estimates that an FMD outbreak in the Golden State alone would result in losses of up to $13.5 billion. Many think that number is too low.

The scourge called classical swine fever shows how easily diseases travel. Epidemiologists believe that a 1997 outbreak in the Netherlands may have spread from Bosnia to Germany through contaminated pork brought in by returning German peacekeeping forces. Improperly treated food scraps from a military base probably spread the disease to local livestock. Infected pigs were then transported on trucks inadequately disinfected between deliveries. In short order, the pathogen was literally driven from Germany into the Netherlands, where the size and density of hog operations transformed the outbreak into a full-scale pandemic.

By 1998, 11 million pigs in the Netherlands had to be destroyed, about two-thirds of the national herd. Now, a similar catastrophe may be brewing in Britain. Biologists say the source is probably pork from Asia. In America, meanwhile, health authorities are watching these developments with alarm. "The Netherlands, Germany, and England all have superb veterinary systems, and they're getting hammered. So why on earth shouldn't it happen to the U.S.?" asks Keith Murray, director of the USDA's National Animal Disease Center in Ames, Iowa.

Beyond accidental transmission looms the very real danger of agroterrorism. Unlike human diseases, which generally require sophisticated manipulation in order to be "weaponized," many animal viruses such as FMD are ready to use as is. They're low-tech, low-cost high-impact, and very difficult to trace. "A person could smuggle in a virus, and they could just go to a feedlot," says Mowafak D. Salman, chair of USAHA's Foreign Animal Disease Committee. "If anything happened to our beef supplies, it would be more devastating [to society] than one or two deaths from West Nile fever."

Agroterrorism has a long history--even in the U.S. During World War I, German agents spread anthrax and glanders viruses in Maryland, Virginia, and New York in an attempt to kill horses and mules destined for Allied troops. By World War II, biowarfare programs had been set up in the U.S., Britain, Japan, Canada, and the Soviet Union. South Africa and Iraq have also had programs. While U.S. policy is to assume agricultural disease outbreaks are naturally occurring, says Floyd P. Horn, administrator of UDSA's Animal Research Service, "we really don't know." It's a point underscored by recent events in Brazil, where investigators say financial sabotage by rival ranchers may be behind a recent FMD outbreak in cattle.

RIGID POLICIES. Well-intentioned global trade policies may actually have weakened protections against bioinvasion. The WTO, for example, has sought to weed out fake health issues that nations sometimes use as ploys to shut out agricultural imports. But in its zeal, the WTO adopted agricultural trade policies that critics say are unrealistic and too rigidly scientific. Proof of a disease threat is often elusive. Free traders and WTO defenders have a different view. "Look at the facts on the ground," says Isi Siddique, senior trade adviser to Agriculture Secretary Daniel R. Glickman. "Have more animal diseases crept into the U.S. than in the years prior to WTO? I don't think so."

Trade policies aside, scientific risk assessments take time, money, and staff. Yet budgets for animal disease research in the U.S. have been stagnant for at least a decade. In Ames, at one of the USDA's most critical lab complexes, the facilities urgently need updating and renovation. According to a recent department report, "virtually every critical system--ventilation, electrical, sewage treatment, biocontainment, incineration, and heating and cooling--is antiquated."

Conditions are not much better at Plum Island, N.Y., the only lab in the U.S. devoted to foreign animal disease research. It has neither the set-up nor staff to run heartwater tests, for example. So the Florida ticks have to be sent to a lab in Harare, Zimbabwe, and it takes five months to get results. "There are services we can no longer provide," complains the USDA's Torres.

Budgets for inspectors have also been pared to the bone. Veterinary Service (VS), the USDA division responsible for safeguarding livestock and poultry health, has just 98 full-time and 28 seasonal inspectors overseeing the import of nearly 17 million animals. And at the U.S. Fish & Wildlife Service (USFWS), there are only 91 field inspectors to process an estimated 20 million animals--200 million including fish. Forty-four positions for criminal investigators tracking animal smuggling are vacant due to lack of funding. "It's pathetic. We really do not have the support structure we need to protect animal agriculture in this country," says Elizabeth A. Lautner, a veterinarian with the National Pork Producers Council and vice-chair of the USDA's Secretary's Advisory Committee on Foreign Animal & Poultry Diseases.

While the U.S. has escaped large-scale animal plagues in recent years, several near-misses suggest that its luck finally may be running out. Since the 1950s, the U.S. has spent tens of millions of dollars eradicating screw worm--a horror story of a maggot that feeds and breeds on the open wounds of both man and beast--down to the southern Mexican border. But last March, a polo pony imported from Argentina, where the scourge is endemic, breezed through a USDA quarantine in Florida, only to have an infestation discovered by a private veterinarian less than 24 hours before the emergence of adult flies.

Exotic Newcastle Disease (END) also looks like a narrow miss. The poultry plague in Mexico was contained. But that doesn't mean there aren't consequences in the U. S. According to a USDA field report, the Mexican operations of U.S.-based Tyson Foods Inc. have borne the brunt of the pest, with more than 80% of the losses. Tyson won't reveal specific costs, but poultry experts estimate the value of lost birds to be at least $11 million. Cleanup, restocking, and lost production time add to the tab. According to the company's Securities & Exchange Commission filings, Tyson's international division posted a $25 million decline in third-quarter profits this year.

END hasn't made its way north--yet. But agriculture experts vividly recall the last outbreak, in the early 1970s, when 12 million birds were destroyed and 46,000 square miles of California and Arizona were placed under quarantine. "You let Newcastle get into the U.S., and people won't be so concerned about the cost of a gallon of gas," says James Grimm of the Texas Poultry Federation. "They won't get any chicken tenders and chicken breasts." The END threat is so serious that in 1996, the mere rumor of an outbreak in Missouri was enough for China to cut off its poultry trade with the state for nearly two months. A full-scale outbreak would "end the export market," says Charles Beard, vice-president for research at the U.S. Poultry & Egg Assn.

WALL STREET WORRIES. So what can be done? Global trade and travel are facts of modern life. But there are signs that Washington and Wall Street now recognize the problem. The threat of a foreign animal disease outbreak could cause investors to flee farm and food stocks. "All it would take is one incident, one company to miss a quarter," says Credit Suisse First Boston analyst David C. Nelson.

On the legislative front, both the House and Senate agriculture sub-committees have recommended allocating funds to redesign the USDA lab complex in Ames. Plum Island is also slated for an overhaul--but political battles may hold up plans to build new, Bio-level 4 facilities to handle agroterrorism research.

On the regulatory front, the USDA has now banned the import of African tortoises known to carry heartwater ticks and restricted intrastate trade. In the meantime, USDA staff are racing to develop a national preparedness program for animal health emergencies. These steps don't begin to answer the kinds of questions that plague the USDA's Torres. "How much risk is acceptable?" he asks. "Is it one incident every 200 years? 25 years? That's the big question, and we don't have a good answer." You can bet scientists and legislators will be working on the problem though. The future of U.S. agriculture depends upon it.