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Policing the Flyways of Disease
From the peculiar vantage point of the U.S. Department of Agriculture, the world beyond America’s borders swarms with pathogenic threats. With more than 2.5 million foreign animals arriving in the United States every year–any one of which may bear the beginnings of an epidemic that could devastate the nation’s livestock–the USDA must practice around-the-clock vigilance. At
major airports and seaports, quarantine officers inspect the daily arrivals of everything from emus and tapirs to Egyptian racehorses, while crack units of green-jacketed canines known as Beagle Brigades sniff out microbial stowaways. Among the dozens of deadly plagues that could slip through, the following represent, in effect, the USDA’s Least Wanted.
Screwworm
The larvae of screwworm flies burrow into the flesh of livestock and feed on it, causing gruesome, expanding wounds that result in severe infections and, if left untreated, death. Having eradicated screwworm from the United States in 1959, the USDA is now trying to push it out of North America entirely. During the spring mating season, the USDA drops millions of sterilized male
screwworm flies from planes over El Salvador, Nicaragua, Costa Rica, and other Central American countries. If an outbreak were to recur in the United States, the cattle industry would sustain annual losses of more than $700 million.
Foot-and-Mouth Disease
Common in Africa, Asia, and South America, this ancient scourge can infect all cloven-hoofed animals, causing blistering of the mouth, teats, and hooves. One of the world’s most contagious viruses, FMD has not struck in the United States since a 1929 outbreak in California. In 1946, however, Mexico suffered a large-scale epidemic in which more than a million cows and hogs had to
be slaughtered
African Swine Fever
A tick-borne hemorrhagic-fever virus that kills pigs in much the same way that the Ebola virus kills humans, ASF is common throughout Africa and has periodically struck in Portugal and Spain. The closest ASF has ever come to U.S. shores was an epidemic in Cuba in the seventies, which was thought to have been caused by Cuban troops returning from the Angolan civil war. After a 1978
outbreak in
Avian Influenza
No country in the world is safe from avian influenza, commonly known as the fowl plague, which causes severe diarrhea and painful clogging of the kidneys, among other symptoms, and nearly always results in death. The disease was first described in Italy in 1878. Today, with the massive size of poultry farms in the United States, even a small incident could rapidly escalate into a
full-scale epidemic. During the last major outbreak in the United States, which occurred in 1983 in southeastern Pennsylvania, the USDA’s Animal and Plant Health Inspection Service had to move in and destroy nearly 20 million chickens in a matter of days.
Exotic Newcastle Disease
This lethal poultry disease, which causes tracheal hemorrhaging, was first identified in 1926 at Newcastle upon Tyne, England, and by 1948 was well estab-lished in the United States. Because the affliction has few symptoms prior to death, farmers whose flocks have been hit with Newcastle commonly suspect mass poisoning. After an outbreak in California in 1957, the USDA imposed
strict quarantine measures on all imported birds, and since then there have been few major recurrences. In 1992, however, USDA agents had to slaughter 27,000 farm turkeys in North Dakota to stem an outbreak that was traced back to infected wild cormorants from the Great Lakes.
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