Chapter 5

Recommendations

In 1917 the United States initiated a campaign to eradicate bovine tuberculosis in order to improve human and animal health. By 1985 the disease had almost been eliminated, but since then further progress has apparently been stalled. The persistence of infection in large dairy herds in the southwest, the apparent rise in the number of infected Mexican cattle imported into the United States, and the appearance of infected bison, elk, and deer in the rapidly growing captive Cervidae industries all contribute to the persistence and enhanced potential for spread of bovine tuberculosis. As a consequence, both the feasibility of attaining the goal of the disease's eradication and the effectiveness of the existing eradication strategy were called into question.

The committee has concluded that the goal of eradication of bovine tuberculosis in the United States is biologically and economically feasible. International experience has shown that the only developed countries that have chosen to live with bovine tuberculosis are those, such as Ireland and New Zealand, where the disease is entrenched in wildlife populations. However, in order to achieve eradication, the existing federal-state cooperative program must be modified.

USDA should vigorously pursue eradication of bovine tuberculosis in cattle, bison, cervids, camelids, and other domesticated or farmed animals. While improvements in tests used to detect infection appear possible and should be pursued, the committee believes existing diagnostic technology is adequate to support a strengthened eradication effort.

Necessary components of a strengthened eradication program aimed at the major disease threats have been identified by the committee and are detailed below.

Systematic analysis of alternative disease control strategies is required. The application of bioeconomic modeling to historical U.S. and Canadian experience with bovine tuberculosis demonstrated the superiority of depopulation compared to test and slaughter as an eradication strategy. Depopulation produced the largest excess of benefits over costs because, in achieving eradication sooner, program costs were smaller and losses from disease were reduced. Although the models reviewed assumed that adequate public funds were available to fully compensate producers whose animals were designated for slaughter, the committee believes this assumption is untenable, given the fiscal constraints faced by governments.

Recognizing the constraints on public funds and the benefits from eradication that accrue to livestock enterprises, the committee recommends that producers of beef and dairy cattle, bison, elk, deer, and other exotic species financially support the eradication program. In sharing responsibility for funding an eradication program with taxpayers, the livestock industry will promote attainment of a mutually beneficial goal and simultaneously acquire a direct interest in ensuring the program is operated effectively.

As one step, selecting the optimal extent of producer participation and the choice of eradication strategy (e.g., depopulation or test and slaughter) could be evaluated with the use



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LIVESTOCK DISEASE ERADICATION: EVALUATION OF THE COOPERATIVE STATE–FEDERAL BOVINE TUBERCULOSIS ERADICATION PROGRAM Chapter 5 Recommendations In 1917 the United States initiated a campaign to eradicate bovine tuberculosis in order to improve human and animal health. By 1985 the disease had almost been eliminated, but since then further progress has apparently been stalled. The persistence of infection in large dairy herds in the southwest, the apparent rise in the number of infected Mexican cattle imported into the United States, and the appearance of infected bison, elk, and deer in the rapidly growing captive Cervidae industries all contribute to the persistence and enhanced potential for spread of bovine tuberculosis. As a consequence, both the feasibility of attaining the goal of the disease's eradication and the effectiveness of the existing eradication strategy were called into question. The committee has concluded that the goal of eradication of bovine tuberculosis in the United States is biologically and economically feasible. International experience has shown that the only developed countries that have chosen to live with bovine tuberculosis are those, such as Ireland and New Zealand, where the disease is entrenched in wildlife populations. However, in order to achieve eradication, the existing federal-state cooperative program must be modified. USDA should vigorously pursue eradication of bovine tuberculosis in cattle, bison, cervids, camelids, and other domesticated or farmed animals. While improvements in tests used to detect infection appear possible and should be pursued, the committee believes existing diagnostic technology is adequate to support a strengthened eradication effort. Necessary components of a strengthened eradication program aimed at the major disease threats have been identified by the committee and are detailed below. Systematic analysis of alternative disease control strategies is required. The application of bioeconomic modeling to historical U.S. and Canadian experience with bovine tuberculosis demonstrated the superiority of depopulation compared to test and slaughter as an eradication strategy. Depopulation produced the largest excess of benefits over costs because, in achieving eradication sooner, program costs were smaller and losses from disease were reduced. Although the models reviewed assumed that adequate public funds were available to fully compensate producers whose animals were designated for slaughter, the committee believes this assumption is untenable, given the fiscal constraints faced by governments. Recognizing the constraints on public funds and the benefits from eradication that accrue to livestock enterprises, the committee recommends that producers of beef and dairy cattle, bison, elk, deer, and other exotic species financially support the eradication program. In sharing responsibility for funding an eradication program with taxpayers, the livestock industry will promote attainment of a mutually beneficial goal and simultaneously acquire a direct interest in ensuring the program is operated effectively. As one step, selecting the optimal extent of producer participation and the choice of eradication strategy (e.g., depopulation or test and slaughter) could be evaluated with the use

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LIVESTOCK DISEASE ERADICATION: EVALUATION OF THE COOPERATIVE STATE–FEDERAL BOVINE TUBERCULOSIS ERADICATION PROGRAM of bioeconomic models updated to reflect the current structure of the livestock industry, public attitudes toward animal welfare and the environment, and human population demographics that affect the transmission of disease. In this context, the extent and kind of financial participation required of producers could be explored. For example, participation could be explicit through payment of premiums into an insurance scheme pooling the risks of disease or implicit through self-insurance when a producer absorbs the uncompensated costs of depopulation. ENDEMIC BOVINE TUBERCULOSIS IN U.S. CATTLE The committee believes a continuing program is necessary to clear infection from the large southwestern dairy herds and prevent their reinfection, and, when necessary, eliminate infection in other dairy and beef herds. Currently, endemic infection is limited to a few large dairy cattle herds in the El Paso, Texas, area where it has become established in approximately 10 dairy herds. To date these herds have not been depopulated nor has the infection been eliminated by a test and slaughter program. The herd owners are reluctant to absorb the costs of depopulation and have concerns about test performance, results, and interpretation that could affect the accuracy of identification of infected animals. There have also been problems tracking cattle movements, and it has not been possible to exclude all known, as well as unknown, risk factors, unidentified potential reservoirs, and unusual routes of transmission as important factors in the persistence of the infection. Consistent with its view that livestock producers are among the beneficiaries of disease eradication, the committee believes that dairy producers should contribute financially to the eradication program. The Need for Combined Efforts The committee is aware of the state-federal-industry meeting that has been held to develop a strategic plan for the eradication of bovine tuberculosis in the El Paso milkshed (U.S. Department of Agriculture, 1992). Successful implementation of that plan could be assured with broad participation of affected producers and livestock handlers and with focused management by USDA. USDA should assemble and assign a field investigation/management team to the El Paso milkshed to perform and or oversee all testing and test interpretation in infected and exposed herds, to ensure accurate animal identification and tracking, as well as appropriate recordkeeping and data collection, to identify key risk factors, and to enforce quarantine as necessary. The team should include the appropriate authorized state and federal officials as well as industry representatives. Ideally, the field team should have the discretion to design eradication measures on an individual farm basis. As part of its investigative function, the team should examine other potential reservoirs or vectors of disease (other species of animals on farms including companion animals and humans). Because of the potential threat to human health and potential to be a reservoir of infection, farm workers, including transient workers, should also be tested. The team would also be responsible for producer and community education regarding the problem.

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LIVESTOCK DISEASE ERADICATION: EVALUATION OF THE COOPERATIVE STATE–FEDERAL BOVINE TUBERCULOSIS ERADICATION PROGRAM One of the responsibilities of the field team should be to assess the feasibility of depopulation as an eradication strategy. The team 's deliberation should be supported by an up-to-date bioeconomic analysis of disease, farm, and industry characteristics, as recommended earlier. Such analysis would help the team reconcile the requirements of an effective eradication strategy with the probable shortage of public funds needed to compensate fully the affected producers. As noted, the committee believes producers should contribute to the program. MEXICAN CATTLE IMPORTS Mexican cattle infected with M. bovis still gain entry into the United States. Given the inadequacies of available tests and the current status of the Mexican tuberculosis program, this situation is not likely to change in the near future. The entry of these cattle, their relatively high lesion rate at slaughter, and the costs associated with their traceback suggest that special effort is needed to solve this problem. In the interests of both the United States and Mexico, the USDA should provide Mexico with epidemiological, laboratory, and training support for bovine tuberculosis control. Also, importers of Mexican cattle should be required to pay costs of post-entry testing, when such testing is deemed necessary, in addition to any general industry levy to support eradication. These recommendations are consistent with the committee's conclusions about the requirements of disease management with more integrated international trade and with the need for the livestock industry to share with taxpayers the costs of eradicating bovine tuberculosis. A coordinating committee of Mexican and U.S. animal health officials, including representatives from producer groups, should be formed and funded to meet on a regular basis. The coordinating committee should be chartered to review and recommend changes in rules governing the importation of Mexican cattle and in regulation of cattle movement within the United States. Uniform regulations controlling postentry movement and identification of Mexican cattle should be adopted by all states. The regulations should require specification of the destination of a shipment and allow shipment only to quarantine pastures, feedlots, or to designated holding areas for retest. Replacement or breeding cattle should not be present in the quarantined facilities, and untested cattle should be released from these designated facilities only for slaughter. Release of cattle for other purposes (for example, rodeos and/or breeding) would be possible only after appropriate postentry negative tuberculosis tests. The committee endorses relaxation of movement and importation requirements commensurate with progress in controlling tuberculosis in the Mexican states of origin. For the foreseeable future, it is vital that individual animal identification of all Mexican-origin cattle be continued (including official Mexican ear tags) to allow tracing to the farm of origin.

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LIVESTOCK DISEASE ERADICATION: EVALUATION OF THE COOPERATIVE STATE–FEDERAL BOVINE TUBERCULOSIS ERADICATION PROGRAM No state or federal indemnity should be provided for reactors of Mexican origin unless the original identification is available. Despite the number of M-branded infected cattle found during slaughter checks, with few exceptions there is little evidence of spread of infection from these steers to other animals (U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services, 1992). If this lack of spread can be confirmed, it might be less costly to place movement restrictions on M-branded animals than to continue to expend time and money to trace the origin of animals with compatible lesions. As an immediate response, traceback should be required only if the APHIS tuberculosis epidemiologist and involved state authorities deem it necessary. Also, if future monitoring confirms a lack of spread of infection, APHIS should consider not submitting lesions and not performing tracebacks on feedlot cattle (subject to the previously mentioned U.S.-Mexican coordinating committee discussions), unless particular problems are noted. This would allow reassignment of effort to areas that could give a better payoff for eradication. TUBERCULOSIS IN CERVIDAE AND CAMELIDAE Mycobacterium bovis infection in Cervidae and Camelidae presents a major threat to disease eradication efforts in cattle, to the health of the cervid and camelid industries, to wildlife, and to public health. Thus, immediate action is required to control this emerging problem. A program for the eradication of M. bovis infection in Cervidae and Camelidae should be established. Funding of basic and applied research designed to lead to better diagnostic tests is recommended, and the industries should be required to finance a portion of the costs of such program. Federal authority to pursue disease eradication in farmed Cervidae and Camelidae should be exercised by APHIS under Uniform Methods and Rules separate from that for Bovidae. These Uniform Methods and Rules for Cervidae and Camelidae should include regulations designed to prevent importation of M. bovis infection. As well, APHIS should establish a state-federal-industry committee to facilitate ongoing communication and program development. In particular, the following issues need to be resolved for farmed cervids and camelids. Testing methodology must be standardized and implemented. Studies, conducted in a manner to generate scientifically valid data for comparative evaluation of tests, must be completed. Sufficient data could be gathered within a reasonable time period (say, 3 years) to allow selection of the most appropriate testing procedures. USDA/APHIS personnel must be trained regarding handling, management, and testing of these exotic species, with special attention to scrutiny of infected animals and premises. Industry and the public must be educated regarding the problem of tuberculosis in these species. As with eradication in other species, an indemnity program supported by taxpayers and industry must be developed to secure cooperation of producers.

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LIVESTOCK DISEASE ERADICATION: EVALUATION OF THE COOPERATIVE STATE–FEDERAL BOVINE TUBERCULOSIS ERADICATION PROGRAM Animals must be removed from herds by slaughter or other fail-safe methods (such as appropriate on-site burial). Where possible, development of a flexible informal monitoring program for M. bovis in ranched and wild cervids should be encouraged. For example, monitoring could be done by regular postmortem examination at slaughter, natural death, or hunter kill. Such a program would provide invaluable information about other diseases as well. ZOO ANIMALS Zoo animals, including primates, cervids, bison, and other bovine, ovine, and caprine (nondairy) species, are currently not included under the UMR for tuberculosis eradication. M. bovis infection in these animals has the potential for interspecies spread, including spread to humans (handlers, caretakers, or visitors). Consideration should be given to including zoo animals under the auspices of the Uniform Methods and Rules. Minimal requirements should include animal identification, movement surveillance, and isolation of reactors. Treatment with appropriate drugs may be considered for endangered and/or valuable infected zoo animals. Discussions with the American Association of Zoological Parks and Aquariums (AAZPA) should be held on this matter, but the policies should also relate to the numerous non-AAZPA zoos and animal holdings. PUBLIC HEALTH Although the risk of M. bovis infection in humans has been greatly reduced by the control of tuberculosis in animals and their products, recent studies continue to indicate that subgroups of the human population still have an unacceptably high risk of infection. Consequently, it is prudent to take measures to minimize the possibility of disease transmission between animals and humans. All confirmed diagnoses of M. bovis in humans or animals should be communicated to federal, state, and local veterinary and medical officials; and M. bovis infection in any species should be a reportable disease in all states. The Centers for Disease Control should differentiate organisms in the M. tuberculosis complex to provide specific identification of all M. bovis isolates. Federal public health authorities should initiate surveillance testing for tuberculosis in all instances in which there is a risk of transmission of M. bovis infection between humans and animals. In addition, public health authorities, together with USDA, should assess the feasibility of instituting educational programs about disease risk for all who have contact with infected or exposed herds.

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LIVESTOCK DISEASE ERADICATION: EVALUATION OF THE COOPERATIVE STATE–FEDERAL BOVINE TUBERCULOSIS ERADICATION PROGRAM For example, farm employees in the El Paso milkshed and workers in at-risk slaughterhouses should be routinely tested for infection. Veterinarians, rendering plant and slaughterhouse personnel, and affected communities should receive information about the human health risks associated with bovine tuberculosis. SLAUGHTER SURVEILLANCE Changes in the domestic meat inspection system may imply the need for accommodation in animal disease control programs. Surveillance via inspection of slaughtered cattle is the key to the ongoing success of the bovine tuberculosis eradication program in cattle. Slaughterhouse operations and inspection processes are undergoing constant change, driven by sanitary requirements, efficiency, and other needs. Thus the committee makes the following recommendations. Slaughter surveillance tests to supplement or replace current visual FSIS inspection should be developed. These tests should be designed to detect infected animals that may not have gross lesions and should be compatible with Hazard Analysis Critical Control Point (HACCP) inspection programs. FSIS personnel need increased awareness as to the essential role of inspection of carcasses for detecting M. bovis infection, and the inspection program should continue at a high level of diagnostic coverage and accuracy. USDA/APHIS should ensure adequate animal identification for traceback of animals. It should also ensure that the man-made identification materials are maintained by and for APHIS. The goal of achieving a submission rate of one lesion per 2,500 feedlot cattle or one lesion per 2,000 adult cattle slaughtered should be reassessed and modified, if necessary, to reflect the probability of infection by type of animal and region and the value of traceback in that animal type. Once these goals are established, every effort should be made to achieve them. RESEARCH AND TRAINING There is always a danger that success in the eradication program removes incentives to learn more about bovine tuberculosis. To give a good example, although existing diagnostic technologies (lesion detection, culture, tuberculin skin tests) have been used successfully in the United States and other countries, there has apparently not been a continuing effort to evaluate their efficiency as patterns of disease change and additional species of animals become infected. Reevaluations are, however, essential to maintaining confidence in the ability to detect disease, which is the first step toward eradication. This lack of knowledge, together with the known practical limitations (time, animal handling, subjective nature, costs) of current tests, may impede progress toward eradication.

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LIVESTOCK DISEASE ERADICATION: EVALUATION OF THE COOPERATIVE STATE–FEDERAL BOVINE TUBERCULOSIS ERADICATION PROGRAM Moreover, as promising new tests become available, it is particularly important to have a good grasp of the performance of the existing tests against which they must be compared. The committee recommends that USDA ensure the ongoing evaluation of new technologies in addition to the routine application of existing tests. For example, combining emerging technologies with a portion of the official tests that the National Veterinary Service Laboratory performs on a regular basis would enable diagnostic technicians to maintain state-of-the-art skills and provide sufficient data to ensure adoption of new official tests as warranted. The committee believes that educating a core of personnel for tuberculosis eradication is essential. To ensure that new programs and technologies are used effectively, the committee recommends that USDA allocate the resources needed to implement formal annual or biannual short courses for current and newly hired animal health personnel (both state and federal) according to their need to know about bovine tuberculosis. Further, the committee urges USDA to maintain a corps of personnel experienced in working with infected animals in the field, including regional veterinary specialists in tuberculosis. With such expertise available, the testing program could reduce its reliance on accredited veterinarians, who, because the infection rate is low nationally, may only infrequently, if ever, be required to administer or interpret a tuberculin skin test. Finally, and consistent with our view of the responsibility of the producing industries, we recommend that the livestock industries and USDA ensure support of a long-term broad-based science-driven program to improve understanding of disease with the ultimate aim of effective control of tuberculosis and other diseases. The program should include research on pathogenesis, immunology, diagnostic approaches, genetic resistance, and epidemiology of these diseases. Because of the financial implications of these programs, they should integrate closely with similar programs in human and comparative medicine. In the long term, bovine tuberculosis will continue to be a problem for the United States, even if it has been eradicated domestically. There will be a continuing need for up-to-date knowledge and technology to protect against reintroduction and/or spread of the infection. Limited knowledge regarding novel or alternate tests and control procedures weakens the credibility of the program, particularly with owners of nonbovine species, and may prevent improvements in the program's efficiency. Newer concepts and technologies consistent with evolving scientific advances will be necessary to meet the expectations of society and the needs of the global livestock industry.

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