One of a private veterinary practitioner’s most critical responsibilities is his or her role as the nation’s front line of defense for detecting emerging, exotic, and transboundary animal diseases (TADs). TADs are important, transmissible diseases of livestock that are not present in 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 wellbeing.
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, and 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, destruction, and disinfection of livestock and poultry infected with these diseases. The list specifically includes “Foot-and-mouth disease, rinderpest, contagious pleuropneumonia, Newcastle disease, highly pathogenic avian influenza, infectious salmon anemia, spring viremia of carp, or 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 CFR reportable disease list, many states require the reporting of additional specific disease conditions. Additional diseases may include those of public health importance, such as equine encephalomyelitis, or other endemic diseases of industry concern, such as bovine trichomoniasis. Licensed 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 SAHO. States may also have 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.In an effort to create a standardized list of animal diseases, the U.S. National List of Reportable Animal Diseases has been proposed. This list, available at https://www.aphis.usda.gov/ aphis/ourfocus/animalhealth/program-overview/ct_national _list_reportable_animal_diseases, is based on the OIE list while complementing the state reportable disease lists.
The World Organization for Animal Health or Office of International Epizootics (OIE)2 is an international organization, representing more than 180 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 for member countries to have rapid situational awareness and to act quickly to protect themselves when outbreaks of OIE-reportable diseases are confirmed in other member countries. More than 115 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, the goal is controlling the TAD outbreak with ultimate eradication and return to preoutbreak 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 significant economic costs associated with disease control and eradication efforts. Direct costs of disease control include paying personnel to manage and control the outbreak, indemnity costs (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. Indirect costs of TAD outbreaks result from control measures such as livestock movement restrictions and biosecurity that disrupt normal business continuity. These are likely to be the most significant economic costs. An example is the reduction or loss of income for a dairy■ 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 (H5N2) 1999—Brucella melitensis
2003— Exotic Newcastle disease
2004— Highly pathogenic avian influenza (H5N2) 2006—Bovine spongiform encephalopathy 2008—Turkey rhinotracheitis
2010—Rabbit hemorrhagic disease
2015— Highly pathogenic avian influenza (H5N2, H5N8)
2016— Vesicular stomatitis virus (New Jersey serotype)
2016— Highly pathogenic avian influenza (H7N8)
2017— Highly pathogenic avian influenza (H7N9) 2017—New World screwworm (Florida)
■ BOX 47.2
Reportable Diseases of Horsesa
African horse sickness
Contagious equine metritis (Taylorella equlgenltalls) Dourine (Trypanosoma equlperdum)
Equine encephalomyelitis (Venezuelan, Eastern, and Western) Equine herpesvirus myeloencephalopathy
Equine infectious anemia
Equine piroplasmosis (Babesla caballl or Thellerla equi) Glanders (Burkholderla mallei)
Hendra virus (Equine morbillivirus)
Japanese encephalitis Piroplasmosis Vesicular stomatitis virus West Nile virus
aThis list will vary by state.
producer who is no longer able to ship raw milk across state lines to a milk processor due to movement restrictions. 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 limit 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 previously. 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. A Foreign Animal Disease Diagnostician (FADD) may be sent to examine the suspect animals and take and submit samples for testing at no expense to the producer or veterinarian. Testing will be prioritized by disease and level of concern. Both the livestock producer and private veterinarian should be contacted with regular updates as test results become available. Hundreds of TAD investigations occur annually in the United States, and fortunately most lead to the determination that a TAD is not involved. The TAD that goes undetected or unreported for some time because of lack of vigilance or reluctance to report will cause major economic harm to the livestock industry and the nation. Veterinary practitioners are encouraged to report a suspected TAD. It is better to investigate and rule out concerns. This not only tests the animal disease emergency response system to ensure that it is as efficient and effective as possible but could also prevent a catastrophic TAD outbreak.