tick, which was eradicated from the United States, but has since developed a resistance to classic methods of control.
New strains of existing diseases, such as highly pathogenic avian influenza and Newcastle disease that could be brought into the United States via imported or migratory birds, and previously unknown diseases like chronic wasting disease also present a growing threat and challenges in terms of new treatment methods. “In the extreme, we have to worry about recombinant organisms … how organisms might be put together or modified to attack, and we hope that extreme scenario is not the one, but it can’t be dismissed,” Rexroad added.
Other speakers discussed how ticks could be used as an agent for the spread of certain diseases such as Texas cattle fever, caused by Babesia bovis, and heartwater, caused by Cowdria ruminantium. Heartwater disease could be spread to deer by the Amblyomma ticks; from there it would “spread geometrically, and it would be really difficult to eradicate,” Brown said.
In areas with disease-spreading tick populations, one could achieve the same results by simply introducing the disease, without having to bring in the ticks, added Dr. Gary Weber, Executive Director of Regulatory Affairs, National Cattlemen’s Beef Association. Another factor, just as important as the disease and the vector, is the development of resistance to insecticides used to control ticks and other vectors. In combination, these factors can complicate control efforts, Weber said.
Animal health issues are very closely linked to food safety and security, Dr. Robert Brackett, Director of Food Safety in the Federal Drug Administration’s (FDA) Center for Food Safety and Applied Nutrition, told the gathering. To illustrate his point, he displayed a list of bacterial and viral risk agents associated with animals (See Box 3-1). The list, published by the Centers for Disease Control and Prevention (CDC), include bacteria, such as the anthrax pathogen, and viruses, such as the one that causes yellow fever, that could be used for bioterrorism.
Brackett said the agency’s traditional approach to inspections of food imports was based largely on volume, i.e., the largest exporters to the United States, such as Canada and Mexico, would have more of their products scrutinized. Now the agency is rethinking that strategy, considering whether to target certain countries or products. The scope of surveillance has also been broadened, with more focus on intentional biologic, chemical, and radiologic threats, he said.
In addition, the FDA no longer assumes that industry and individual producers are concerned only with unintentional contaminants in foods, Brackett