030612 Animal-Borne Illnesses Abound

Mad cows. Masked palm civets. Gambian giant rats. What sound like whimsical characters in a children's book are, instead, the vectors of three new human plagues: variant Creutzfeldt-Jakob disease, SARS and monkeypox.

If recent medical headlines read like parts of a veterinarian's log, it's hardly surprising. Throughout the millennia, animal diseases have been the leading scourges of Homo sapiens. Zoonotic infections -- those that leap from animals to humans -- always shadow societal advances. Whatever novel pandemic next sweeps the world, odds are it will have jumped to us from our vertebrate cousins -- just as the AIDS virus, which may turn out to be the most deadly human pathogen in history, apparently jumped from sub-Saharan primates.

Lately, these afflictions have been on the rise. Of the more than 30 new infectious diseases scientists have uncovered in the past quarter century, all but a few have come from animals. In addition to the most recent ones in the headlines, the short list runs from West Nile encephalitis, Lyme disease and hantavirus pulmonary syndrome to Ebola fever, Nipah virus encephalitis and potentially pandemic strains of avian influenza.

Worse, scientists predict that new animal-borne infections will abound even more in the coming years, as the settings that foster the transfer of germs proliferate.

These risky environments are spawned by the inexorable changes of modern life. The careless development of rich ecological areas such as the rain forests will bombard humans with more novel animal viruses that can strike with fury. Crowded and unsanitary mega cities around the globe will serve as the incubators for these unfamiliar organisms.

After the viral origins of AIDS were mapped, researchers theorized that human forays into untouched areas of Africa were especially risky. But as we've seen with the arrival of the monkeypox in the United States, we don't have to traipse into a rain forest to encounter the threat; by importing exotic rodents, we can bring the rain forest to us.

Faster global transportation will ferry exotic germs anywhere on earth within 36 hours. West Nile virus, believed to have been originally harbored in an Israeli farm goose, arrived in New York City in 1999 -- whether by jet-borne mosquito, human or bird, nobody knows. This year, it will likely show up in all 48 contiguous states, sicken thousands and kill hundreds of Americans.

The massive consolidations of agriculture and food manufacturing will amplify contaminated meat or poultry into worldwide epidemics ---- just as food-borne outbreaks of such agents as E. coli O157:H7, salmonella and campylobacter arise regularly today from the consumption of undercooked beef and chicken.

Experimental medical techniques such as xenotransplantation -- using animal organs in humans - - may plant new pathogens into those who receive the organs. On the maliciously experimental side, many potential agents of bioterrorism, such as the anthrax bacillus, may originate in animals.

For good or for ill, new afflictions are the price of progress. When our ancestors climbed down from the trees to the savanna 5 million years ago, they picked up parasitic worms from animals. The push from Africa to Europe and Asia brought bubonic plague from rats and brucellosis from wild game. With the rise of agricultural settlements, domesticated animals supplied a new crop of germs: We caught measles from dogs, the common cold from horses and tuberculosis from cattle.

In the U.S., recent animal-borne diseases have insinuated themselves into our daily lives and fears. Although we haven't seen within our borders any cases of mad cow disease or homegrown instances of its human byproduct, news of the infection in Alberta, Canada, is too close for comfort. The nation continues to brace for SARS, which made the cross-species vault in China's Guangdong province last November and swiftly spread worldwide. And though the Gambian giant rat, an exotic pet import, has been fingered as the culprit behind the Western-hemisphere debut of monkeypox, the virus actually jumped to people from prairie dogs and rabbits -- suggesting that the infection could become an endemic threat if seeded by those animals in the wild.

We have learned from this onslaught that rapid technological and societal changes give emerging zoonotic agents their opportunities. As long as we continue to create more intersections between us and novel bugs, we will be in trouble.

The good news is that our newfound commitment to public health already has paid off by containing the recent wave of epidemics. Thanks to vigilant surveillance, swift hospital interventions and timely communications, the United States has not seen any SARS deaths. Because of the heightened awareness of smallpox, the monkeypox cases were quickly diagnosed, and the smallpox vaccine will be offered to exposed individuals.

But our defenses are not unassailable. The Centers for Disease Control and Prevention, the leading federal public health agency, has been stretched to the limits by waves of recent outbreaks. Yet, inexplicably, President Bush's requested fiscal year 2004 budget would cut funding for the CDC's infectious-disease-control and epidemic services and response. That would mean fewer researchers in Atlanta, where it is based, and fewer epidemiologists in the field. Meanwhile, state and local health departments have seen their budgets slashed in response to the weak economy. And experts in the ecology of disease-carrying animals and insects are in woefully short supply.

Germs are natural vagabonds. As mad cow disease, SARS and monkeypox have proved, we will always be a step behind emerging organisms. In this sense, we will never know true “homeland security” without a robust public health system.

If only federal officials were reading the headlines: The greatest terrorist of all remains nature itself.

Madeline Drexler is a Boston-based journalist and author of Secret Agents: The Menace of Emerging Infections.

RETURN TO HOME PAGE

E-mail: sflanagan@sprintmail.com