Chapter 47

Prevention, Detection, and Response to Transboundary (Foreign) Animal Diseases

Pamela Joanne Hullinger, Consulting Editor

Perhaps a private veterinary practitioner’s most critical responsibility is his or her role as the nation’s front line for detection and defense against exotic and transboundary animal diseases (TADs). These are important, transmissible livestock diseases that are presently absent from the United States. If introduced, they would cause significant adverse economic or national animal, public, or environmental health consequences. Although many of these disease threats are known, new or “emerging” diseases may also impact the United States and affect human, animal, or ecosystem well-being. The U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS), Veterinary Services (VS) has primary responsibility for addressing foreign and emerging diseases of livestock and poultry, and works closely with state animal health officials (SAHOs), private veterinary professionals, and the livestock industry to monitor for and to detect, control, eradicate, or mitigate the impacts of TADs on the livestock industries and the public. Box 47-1 shows a list of the diseases successfully eradicated from the United States. The Code of Federal Regulations (CFR), Title 9, part 53¹ details the federal government’s list of reportable diseases of livestock and poultry and its policies and procedures for the diagnosis, appraisal, euthanasia, and disinfection of livestock and poultry infected with these diseases. The list specifically includes foot-and-mouth disease (FMD), rinderpest, contagious pleuropneumonia, exotic Newcastle disease (END), highly pathogenic avian influenza (HPAI), and “any other communicable disease of livestock or poultry that in the opinion of the Secretary constitutes an emergency and threatens the livestock or poultry of the United States.”¹ In addition to the federal reportable disease list, many states require the reporting of additional specific disease conditions beyond those named in the Code of Federal Regulations (CFR). Additional diseases specified by states may include diseases of public health importance, such as equine encephalomyelitis, or other endemic diseases of industry concern, such as bovine trichomoniasis. Licensed, practicing veterinarians are responsible for maintaining a familiarity with the federal reportable disease list as well as those of the states in which they practice. The reportable disease list for each state can be obtained through the office of the state veterinarian. States may also have their own more specific policies and procedures for the diagnosis, appraisal, euthanasia, and disinfection of livestock and poultry infected with such reportable diseases. Box 47-2 lists some reportable diseases of horses.

Box 47-1

Years When Foreign Animal Diseases Were Eradicated from the United States

1892—Contagious bovine pleuropneumonia

1929—Foot-and-mouth disease

1929—Fowl plague

1934—Glanders

1942—Dourine

1943—Texas cattle fever

1959—Vesicular exanthema

1959—Screwworm (southeastern United States)

1966—Screwworm (southwestern United States)

1971—Venezuelan equine encephalitis

1973—Sheep scabies

1974—Exotic Newcastle disease

1978—Classical swine fever

1985—Highly pathogenic avian influenza

1999—Brucella melitensis

2003—Exotic Newcastle disease

2004—Highly pathogenic avian influenza

2006—Bovine spongiform encephalopathy

2008—Turkey rhinotracheitis

2010—Rabbit hemorrhagic disease

Box 47-2

Reportable Diseases of Horses *

African horse sickness

Contagious equine metritis

Dourine

Equine infectious anemia

Equine viral arteritis

Glanders (Burkholderia mallei)

Hendra virus

Japanese encephalitis

Piroplasmosis

Venezuelan equine encephalomyelitis

Vesicular stomatitis virus

^* This list will vary by state.

The World Organization for Animal Health, Office of International Epizootics (OIE)² is an international organization, representing more than 167 member countries, that seeks to provide leadership and guidelines to ensure transparency and solidarity in the management of the global animal disease situation. The OIE publishes health standards for international trade in animals and animal products as well as criteria for the validation and certification of diagnostic assays. Policies and procedures that the federal government implements to manage the intrusion of TADs into the United States are often aligned with the OIE health standards and guidelines to help ensure the most rapid and efficient recovery of U.S. exports. Another equally important function of the OIE is to provide an early warning system to enable countries to have rapid situational awareness and to act quickly to protect themselves when outbreaks of OIE-reportable diseases are confirmed in member countries. More than 130 animal diseases are reportable to the OIE. It is important to remember that some of the domestic diseases that are present in the United States, such as bluetongue, are reportable to the OIE and have implications on U.S. trade with countries that are free of those diseases.

To protect the long-term overall health and viability of U.S. animal agriculture, any incursion of a TAD must be rapidly identified and controlled. In the United States, ideally control of an outbreak of a TAD leads to the complete eradication of the disease and return to pre-outbreak disease status. These TAD eradication efforts present significant short-term costs to affected industries as well as the government and the public. In some cases these effects become long term, lasting for years, and industries may never fully recover. Most TAD incursions have a significant economic cost associated with disease control and the eradication efforts. The costs associated with TAD control include the direct costs of disease control as well as the potential loss of foreign trade and the indirect costs to the affected industries that result from the implemented control measures, such as livestock movement restrictions and biosecurity. Direct costs to the government include personnel costs, indemnity costs (cost to buy diseased animals from producers for destruction), and the cost of necessary supplies and equipment for euthanasia, carcass management, and disinfection. In addition to these direct control costs, one of the most immediate consequences of a TAD occurrence in the United States would be the loss of export markets and disruption of normal industry business continuity in the United States. The indirect costs to the affected livestock sectors and other affected industries that would result from the disruption of the normal business continuity are likely to be the most significant economic costs. One example of an indirect cost or loss associated with disease control may be the reduction or loss of income for a dairyman who is no longer able to ship his raw milk across state lines to his customary milk processor. For all TADs, early detection and rapid application of situational awareness to assess the extent of the outbreak, followed by efficient implementation of necessary controls to minimize further spread, will minimize the overall impact of the outbreak on the affected producers, the affected industries, and the U.S. economy as a whole.

The risk of a TAD incursion into the United States today is much greater than it has been in the past, for two main reasons. First, there has been a rapid expansion of international trade and travel. With a greater volume of people, animals, and animal products entering the United States on a daily basis, the opportunity for a TAD to be unintentionally introduced is much higher than it has been in the past. Second, in the wake of the terrorist attacks in the United States on September 11, 2001, there is heightened awareness and concern about the possibility of agroterrorism, or the deliberate introduction of a biologic agent targeting livestock for the purposes of inflicting economic damage and societal instability in the United States. Whether a TAD is intentionally or unintentionally introduced, the detection of the first case as soon as possible is critical to minimizing the overall impact of the resulting outbreak.

Private veterinary professionals need to be familiar with the clinical signs associated with TADs, especially those that can be easily confused with clinical signs of domestic or endemic diseases. When veterinary professionals are concerned about the possibility of a TAD in clients’ animals, they need to contact a federal or state animal health official, who will consult with them on the history of the herd or flock and then may examine the affected animals and take and submit necessary samples for testing at no expense to the producer or veterinarian. Testing will be prioritized by disease and level of concern after understanding the history and clinical status of the livestock of concern. Both the livestock producer and private veterinarian should be contacted with regular updates as test results become available. Several hundreds of investigations such as these occur annually in the United States, and fortunately most lead to the determination that a TAD is not involved. It is the TAD that goes undetected or unreported for some time because of lack of vigilance or reluctance to report that will cause major economic harm to the livestock industry and the nation. Veterinary practitioners should not be concerned about reporting a suspected TAD and having it turn out to be a domestic disease problem, since it is important that the animal disease emergency response system be tested regularly to ensure that it is as efficient and effective as possible. Most importantly, the impact of a delay in detection of a true TAD could be catastrophic.

U.S. Department of Agriculture National Veterinary Accreditation Program³

The USDA established the national veterinary accreditation program in 1907 to provide a mechanism to enable private veterinary practitioners to work on behalf of the federal government to certify animals for certain types of interstate and international movement and to assist in controlling damaging animal diseases. The current mission of the National Veterinary Accreditation Program (NVAP) is to ensure the health of the nation’s livestock and animal population and to protect public health and well-being. NVAP’s goal is to maintain the effective cooperation and use of private veterinary practitioners for regulatory work in a manner that is consistent with international trade requirements and enables the safeguarding of animal health. APHIS VS administers the NVAP. Participation in NVAP is voluntary and is not mandated by the federal government. Box 47-3 provides a list of the requirements for a veterinarian wishing to become accredited by the USDA. Accredited veterinarians participating in NVAP must carry out their duties according to the Standards for Accredited Veterinarian Duties described in CFR Title 9, Part 161. Box 47-4 lists the standards for accredited veterinarians. USDA veterinary accreditation is specific to a given state, so one needs to contact the USDA APHIS VS office in the state where he or she is practicing to obtain accreditation in that specific state. One requirement of USDA VS for accredited veterinarians is reporting of all suspected TADs to state or federal animal health officials for evaluation and any necessary testing. Box 47-5 lists some of the clinical signs that should alert a private veterinarian that a TAD should be considered.

Box 47-3

U.S. Department of Agriculture (USDA) Accreditation Requirements