November 12, 2001

LINCOLN, Neb. — While bioterrorist attacks on Nebraska agriculture may seem unlikely, it's a serious concern. University of Nebraska agricultural specialists say vigilance and preparation can help protect the state's leading industry.

For livestock producers, good biosecurity practices are key to preventing potential terrorist acts and minimizing damage should an attack occur, said David Smith, an NU beef and dairy veterinarian.

"It is a serious concern that our livestock could be deliberately exposed to disease-causing infectious agents or dangerous chemicals," Smith said. "The resulting losses may include animal suffering, debilitation or death, economic damage to our markets at home and abroad or danger to public health from an unsafe food supply."

Many livestock producers implemented tighter biosecurity policies as a preventative tactic earlier this year in response to overseas outbreaks of foot-and-mouth disease and bovine spongiform encephalopathy, or mad cow disease. Continuing and even stepping up these safety measures is a good idea at this time, the Institute of Agriculture and Natural Resources specialist said.

"Check livestock frequently and look for unusual signs of disease," Smith said. "Call your veterinarian if you observe higher than ordinary rates of death or disease."

Of particular concern are animals with blisters or sores around the mouth, udder or feet, severe lameness, abortions or sudden deaths. These symptoms can be indicative of highly contagious foreign animal diseases such as foot-and-mouth disease.

"Livestock illness and death may be noticed before authorities become aware of human health problems due to the same exposure," he said. "Report your concerns. Don’t wait to see if things will look better in a day or two."

To prevent spreading disease from place to place, carefully inspect all animals that are bought or sold, Smith said.

"If something doesn’t look right, call a veterinarian before the animals leave your property," he said. "Also be sure that you follow livestock movement laws. If the animals need health papers, be sure they have them."

Smith suggested producers talk with feed suppliers about the safety of feed that comes onto the farm or ranch and store feed in a secure location.

"Post signs that restrict access to your livestock and direct legitimate visitors to check in at the office," Smith said. "Keep an eye out for people who don’t belong on your place or your neighbor’s. Call law enforcement if you suspect a problem."

Producers should carefully control the contact visitors have with livestock and insist that guests wear clean clothes, he said.

"The bottom line is that if someone wants to introduce a disease to the livestock population, they will find a way to do it," Smith said. "Our job is to be vigilant about biosecurity and report any abnormalities to veterinarians or law enforcement immediately so that we can prevent any problems from spreading."

Insects also present a bioterrorism risk, NU Entomologist Leon Higley said.

"There have been claims about the use of insects as terrorism agents dating back to the Civil War," he said. "There are definitely insects that we wouldn't want here, that pose serious risks to Nebraska crops and livestock."

Many of the most important economic insect pests in North America are introduced, not native, Higley said.

"This country deals with new insect pests all the time because of commerce," he said. "For that reason, it would be difficult to find out if someone did introduce a pest. We wouldn't know whether it was done on purpose or came in through trade."

Insects that can infect livestock are a concern, as are foreign crop pests.

"There are insects that attack soybeans that exist elsewhere in the world that we have the right environmental conditions for right here in Nebraska," Higley said. "Damage to livestock and crops would cause economic loss, as would the quarantines that would be put into place if certain pests were found in the state."

Higley said the U.S. Department of Agriculture's Animal and Plant Health Inspection Service has many tools to prevent the entry of foreign pests and to manage infestations that should occur.

"The best thing producers can do is stay informed about insect problems in their livestock and crop production systems," Higley said. "Should an unusual pest appear, promptly informing extension educators or the state department of agriculture is essential for recognizing new pests and taking appropriate action."

When it comes to crop diseases, John Watkins, an NU plant pathologist, said it's possible but far more difficult to create an artificial disease epidemic in plants than in humans or livestock.

"To understand how difficult it is to create an artificial plant disease epidemic under field conditions, one must only look at one of the basic principles of plant pathology, the plant disease triangle," Watkins said. "For any plant disease to occur and then become epidemic, three essential components must be in balance: a virulent pathogen, a susceptible host and a favorable environment. This doesn’t often occur in nature."

Natural plant disease epidemics happen every year in Nebraska. This year, certain varieties of winter wheat were infected with stripe rust.

"Statewide, losses to stripe rust were probably less than 1 percent," he said. "Our losses to stripe rust were probably less than those of other states because most of our winter wheat acreage was planted to resistant varieties. Only those fields with susceptible varieties were significantly affected."

Gray leaf spot of corn also is a good example of natural disease control.

"Gray leaf spot is the most common and serious corn disease in the Midwest," Watkins said. "This year, dry weather early in the season delayed initial disease development so that when gray leaf spot began to cause damage in most fields, yields had already been determined by plant development. Therefore, the effects of the disease on crop production were minimal."

These examples show why it would be difficult for terrorists to create an artificial plant disease epidemic that would devastate a crop over a wide geographic area, even with a highly contagious or aggressive disease-causing virus, bacteria or fungus, Watkins said.

"There is a wide genetic diversity in our food, feed and fiber crops," he said. "This environment is variable and generally discourages disease development. Also, the fact that most crops are only susceptible to infection during a few months of the year, as opposed to humans and livestock who are susceptible year-round, makes it less likely that plant pathogens would be used as bioterrorism agents."

For more information, consult NU Cooperative Extension NebFact NF01-492, Protecting Livestock from Terrorism, available at local county extension offices or on the web.

11/12/01-HC

John E. Watkins - Ph.D.
Plant Pathology
Professor
(402) 472-2559

Leon Higley - Ph.D.
Entomology
Professor
(402) 472-8689

Heather Corley
IANR News and Publishing
(402) 472-3030

Department: Entomology|Plant Pathology|Veterinary and Biomedical Sciences