A Review of the Bovine Tuberculosis
International Review of Bovine
Tuberculosis in the
State of Michigan
Report of the Meeting of the Bovine Tuberculosis
International Review Team Held October 16 – 18, 2003
Town and Country Hotel
San Diego, California
Dr. Graham J. Hickling, Department of Fisheries & Wildlife,
Michigan State University
Michael S. VanderKlok D.V.M., Animal Industry Division,
Michigan Department of Agriculture
International Review of Bovine
Tuberculosis in the
State of Michigan
Dr. Graham J. Hickling, Department of Fisheries & Wildlife,
Michigan State University
Michael S. VanderKlok D.V.M., Animal Industry Division,
Michigan Department of Agriculture
Executive Summary
The United States Department of Agriculture, in conjunction with the Michigan Department of Agriculture and Michigan Department of Natural Resources, convened a team of international experts to review the current status of the Michigan Bovine Tuberculosis Eradication Program. This panel was comprised of bovine tuberculosis officials and researchers worldwide, with expertise in the control and eradication of bovine tuberculosis, including members from countries with the presence of the disease in both free-ranging and livestock populations.
The team members presented an overview of the history of tuberculosis control and research in their geographical areas, including measures used and lessons learned. After two days of presentations from the assembled team, the third day of the meeting was turned over to a group discussion led by a professional moderator. The focus of this discussion was to investigate what implications emerging science in the area of bovine tuberculosis control and eradication might have, and how the experience of the participants in managing bovine tuberculosis in a variety of wildlife species in other countries might help to guide Michigan’s bovine tuberculosis eradication strategy.
The group discussion identified many issues that will be important as Michigan continues to work on eradicating bovine tuberculosis. Three major areas of discussion were identified: Livestock disease and management programs, strategies for controlling and eliminating the disease in wildlife, and understanding the transmission of the disease within and between species. Gaining and maintaining stakeholder support for eradication was considered by the group to be critical for success, and specific activities associated with eradication should be evaluated partially based upon their effect on this support.
Control of bovine tuberculosis in livestock was discussed, and the group identified that current activities need to be based upon the fact that an alternative source of infection was present, separate from historical livestock methods. The interface between wildlife and livestock, and the development of strategies to reduce the transmission risk between the two, was considered important. In addition, programs and protocols enacted for livestock (as well as wildlife) should consider whether they facilitate elimination of the disease, or provide incentives to “live with” the disease.
Wildlife disease control was seen as a critical component of eliminating bovine tuberculosis. A major requirement for achieving success in wildlife disease eradication is maintaining stakeholder support, in the face of the need for long-term interventions. The length of time necessary to obtain eradication success will be dependent upon how long it takes to reach and maintain a minimum density of animals. In addition, focusing on the areas with the highest disease prevalence will speed up the eradication program. Tuberculosis control in other countries has been hindered by periods of decreased focus and activity, resulting in more extensive outbreaks of disease. These subsequent outbreaks resulted in greatly increased resource inputs to regain control. Michigan was identified to be at a critical stage where adequate resources and activities can be successful in eliminating the disease. If the disease becomes more entrenched, the potential for success may decrease rapidly.
Disease transmission between species was identified as being different among countries, and is an area of uncertainty for many programs. Consideration must be given to the potential that multiple transmission routes are present, and there is likely a knowledge gap in the area of transmission between livestock and wildlife. The program must consider reducing transmission risk between these species, and the interface between livestock and wildlife should be an area of focus.
The subject of vaccination for bovine tuberculosis in livestock or wildlife received much discussion. It was indicated that vaccine usage in livestock may not be an optimal use of resources in areas of relatively low disease prevalence, and has a risk of diverting focus from other critical control measures identified. The concept of tuberculosis vaccination in wildlife is an emerging area of research that may warrant further investigation. Any usage in wildlife would have many impediments to implementation that would take considerable time to resolve. Tuberculosis control in Kruger National Park will soon begin to include vaccination of some wildlife species, and may provide a useful test of this concept.
The group identified other areas of focus that will be critical to success in Michigan. These issues included focusing on development of creative ways to reduce the risk of transmission at livestock/wildlife interfaces, while maintaining pressure on eliminating the disease from wildlife. Success in livestock populations may depend upon the industry being supported as part of the solution to the problem, as opposed to a victim of the situation. There needs to be long term focus on communication efforts, including stakeholders within and between states, to ensure that understanding and support for the program is consistent.
Although the problem remains challenging, the tuberculosis situation in Michigan has advantages over comparable programs in many other countries. The disease is not expanding rapidly into new areas, and the main infected wildlife species can be intensively managed for transmission risks and population densities. The members commended the USDA for convening the meeting, considered a valuable opportunity and resource for all the involved parties and affiliated programs.
I. Introduction
Bovine tuberculosis (TB) was once widespread among U.S. livestock. The United States Bovine TB Eradication Program began in 1917 and proved highly effective in controlling the disease. By the 1960s the number of TB-reactor cattle being detected in Michigan was declining rapidly and by 1979 the State had declared itself bovine TB ‘accredited free’.
At that time the extent of bovine TB in Michigan wildlife was unstudied. In contrast to the situation with domestic livestock, the disease appears to have been rare in most wild species over the past century. Prior to 1995 there had been only eight cases of bovine TB reported in wild deer from throughout North America (Schmitt et al. 1997).
In 1975, a tuberculous wild white-tailed deer was shot by a hunter in the Northeastern Lower Peninsula (NLP). In 1994, a second tuberculous deer was shot in Alpena County, nine miles from the location of the first case. Wildlife surveys conducted in the spring and fall of 1995 detected further cases among wild deer. Since then, extensive annual surveillance has established that persistent TB infection is present at greater than 2 percent prevalence among deer in a ‘core area’ of 15-20 townships on the shared boundary of Alpena, Alcona, Oscoda and Montmorency Counties in the Northeastern Lower Peninsula (NLP) of Michigan.
In 1998, cases of bovine TB infection began to re-emerge among livestock in the counties surrounding the core area. As a consequence of this resurgence in TB among livestock, Michigan lost its bovine TB ‘accredited-free’ status in June 2000 and is currently designated as having ‘modified accredited’ status.
The United States Department of Agriculture’s (USDA) stated intention is ‘to eradicate bovine tuberculosis from the domestic livestock population of the United States’ (APHIS 2000). This implies that all states need to achieve, and maintain, tuberculosis accredited free status. Thus, there is pressure for Michigan to eradicate tuberculosis from its wildlife population so as to prevent transmission of the disease from wildlife to domestic livestock. Michigan hunters and the public are also concerned at the risk the disease poses to the wild deer population. Michigan has consequently implemented a wide range of management activities to combat the current disease problem:
- Prevention of within- and between-herd transmission of infection by livestock through herd testing and depopulation, restrictions on livestock movement, and slaughterhouse surveillance;
- Prevention of transmission of infection from wildlife to cattle through increased harvesting to reduce wildlife population numbers, and changes in farm management practices such as fencing and feed storage;
- Reducing, and if possible eradicating, bovine TB infection from wildlife through wildlife population reduction, and restrictions on supplemental feeding and baiting that cause wildlife to congregate.
These management actions were implemented progressively in the late 1990s. It is therefore of considerable concern to all parties that since 2000 there has been no evidence of any significant decline in TB prevalence among wild deer, nor any abatement in the number of cattle herds becoming infected with the disease.
In mid-2003, concern at the lack of progress towards TB eradication led Dr. Joan M. Arnoldi, State Veterinarian, Animal Industry Division, Michigan Department of Agriculture; and Rebecca Humphries, Chief of the Wildlife Division, Michigan Department of Natural Resources, to invite an international panel of bovine TB researchers and managers to meet in San Diego, California to review the bovine TB situation in the state of Michigan. The focus of the meeting was to consider the latest research and management findings in the U.S. and overseas, and to consider the prospects for new or enhanced strategies for TB eradication.
The meeting aimed to summarize the best ideas and understanding of the international team in a report that could be brought back to Michigan to assist the state officials charged with developing an enhanced bovine TB Eradication Strategy during 2004.
II. Meeting Participants
Dr. Joan M. Arnoldi
Michigan Department of Agriculture
Animal Industry Division
P.O. Box 30017
Lansing, Michigan 48909
E-MAIL:
PHONE: (517) 373-1077
FAX: (517) 241-4502
Dr. Roy Bengis
Veterinary Investigation Centre
P.O. Box 12
Kruger National Park
Kruger 1350 South Africa
E-MAIL:
PHONE: 27 13 735-5641
Dr. Carole Bolin
Michigan State University
A3A Veterinary Medical Center
East Lansing, Michigan 48824-1314
E-MAIL:
PHONE: (517) 353-2296
FAX: (517) 432-9813
Dr. Leigh A.L. Corner
University College Dublin
Department Large Animal Clinical Studies
Belfield, Dublin 4
Ireland
E-MAIL:
PHONE: 353 0 1 716-6070
Dr. Tom Deliberto
USDA, APHIS, Wildlife Services
National Wildlife Research Center
4101 LaPorte Avenue
Fort Collins, Colorado 80521-2154
E-MAIL:
Dr. John Fischer
University of Georgia
College of Veterinary Medicine
Southeastern Cooperative Wildlife Disease Study
Athens, Georgia 30602-7387
E-MAIL:
PHONE: (706) 542-1741
Dr. Michael J. Gilsdorf
National Animal Health Policy and Programs
Veterinary Services, USDA, APHIS
4700 River Road, Unit #33
Riverdale, MD 20737-1231
E-MAIL:
PHONE: (301) 734-6954
FAX: (301) 734-7964
Professor Frank Griffin
University of Otago
Department of Microbiology
Deer Research Laboratory
P.O. Box 56
Dunedin New Zealand
E-MAIL:
PHONE: 64 03 479-7710
FAX: 64 03 477-2160
Dr. Graham Hickling
Michigan Department of Natural Resources
Rose Lake Wildlife Research Station
8562 East Stoll Road
East Lansing, Michigan 48823
E-MAIL:
PHONE: (517) 373-9358
FAX: (517) 641-6022
Ms. Rebecca Humphries
Michigan Department of Natural Resources
Wildlife Division
P.O. Box 30028
Lansing, Michigan 48909
E-MAIL:
PHONE: (517) 373-9311
FAX: (517) 373-6705
Dr. Paul Livingstone
Animal Health Board
P.O. Box 3412
Wellington, New Zealand
E-MAIL:
PHONE: 64 4 474-7804
FAX: 64 4 473-8786
Dr. Reed Macarty
USDA APHIS VS
3001 Coolidge Road, Suite 325
East Lansing, Michigan 48823-6337
E-MAIL:
PHONE: (517) 324-5290
FAX: (517) 324-5289
Dr. Graham Nugent
TB Epidemiology and Management Landcare Research
P.O. Box 69
Lincoln 8152
New Zealand
E-MAIL:
PHONE: 64 3325 6701 X 2256
Dr. Dan O'Brien
Michigan Department of Natural Resources
Rose Lake Wildlife Research Station
8562 East Stoll Road
East Lansing, Michigan 48823
E-MAIL:
PHONE: (517) 373-9358
FAX: (517) 641-6022
Dr. Mitchell Palmer
USDA, National Animal Disease Center, ARS
2300 Dayton Avenue
Ames, Iowa 50010
E-MAIL:
Dr. Steve Schmitt
Michigan Department of Natural Resources
Rose Lake Wildlife Research Station
8562 East Stoll Road
East Lansing, Michigan 48823
E-MAIL:
PHONE: (517) 373-9358
FAX: (517) 641-6022
Moderator:Ben Peyton
Michigan State University
Department of Fisheries and Wildlife
165 Natural Resources
East Lansing, MI 48824-1222
E-MAIL:
PHONE: (517) 353-3236
III. Schedule of Review Team Presentations
Thursday October 16, 2003
1.Dr. Joan M. Arnoldi: Bovine Tuberculosis in Michigan Livestock
2.Dr. Reed E. Macarty: USDA Support of the Michigan Tuberculosis Program
3.Dr. Stephen M. Schmitt: Bovine TB in Michigan’s Wildlife
4.Dr. Carole Bolin: MSU-CVM Bovine TB Research
5.Dr. Mitchell Palmer: Bovine Tuberculosis Research, Agricultural Research Service, USDA
6.Dr. Thomas DeLiberto: Ecology of Mycobacterium bovis in Michigan
7.Prof. Frank Griffin: Diagnosis of Mycobacterial Diseases in Deer
8. Dr. Roy G. Bengis: Bovine Tuberculosis in Free-ranging Wildlife in the Kruger National Park
Friday October 17, 2003
9.Dr. Paul G. Livingstone: Bovine TB Research and Management in New Zealand
10.Mr .Graham Nugent: TB in Red Deer and Other New Zealand Wildlife: Some Recent Research
11.Dr. Alick Simmons: Bovine Tuberculosis in Great Britain
12.Dr. Stacey Tessaro: Mycobacterium bovis in Canadian Wildlife
13.Dr. Graham J. Hickling: Prospects for Successful Management of Bovine Tuberculosis in Michigan
14. Dr. Leigh A.L. Corner: Natural Infection, Minimum Dose, and Experimental Infection
15. Dr. Phil Elzer (presented by Dr Carole Bolin): A Multivalent Vaccine for Protection Against Brucellosis and Tuberculosis
16. Dr. E. Thomas Thorne: Conflicts in Authority and Strategies to Address Wildlife Disease Issues (Verbal presentation only)
17. Dr. John Fischer: Assessing and Managing Disease Risks in Wildlife.
18.Dr. Micheal J. Gilsdorf: USDA, APHIS Perspective
19.Dr. Stephen M. Schmitt: A New Strategy to Control TB in Michigan Wildlife
IV. Summary of Formal Presentations
Dr. Joan M. Arnoldi: Bovine Tuberculosis in Michigan Livestock
Historical overview: Michigan entered the Bovine Tuberculosis (TB) Eradication program in 1917, and by 1979 had achieved TB Free State status. In 1994 TB was identified in wild deer in Northeastern (NE) Lower Michigan. Whole herd testing of any cattle, goat, or cervid farm within five miles of any tuberculous positive free-ranging deer was then instituted.
In December 1997, TB was confirmed in a privately owned deer herd, leading to the institution of mandatory statewide surveillance of captive cervid herds in January 1999. From January 1, 1998, – October 11, 2003, a total of 31,334 live animal tests and 3,286 slaughter tests were conducted in captive cervid herds statewide, but no further TB cases were found.
In July 1998, a small beef herd in NE Lower Michigan was found to be infected. This led to mandatory testing and movement restrictions so that by January 2000 a statewide surveillance program for cattle and goats was in place. This involved herd testing for three consecutive years in high risk areas, and a goal of testing all herds in the state by December 31, 2003.Dairy herds were tested first, in part because many of the beef herds are small and difficult to locate. Whole herd or individual animal testing, and official identification, are required before animal movement is permitted.
In March 2002, the state was divided into three zones: Infected (with annual whole herd testing of 688 herds), Surveillance (with biannual whole herd testing of 411 herds), and Disease Free. Disease Free counties adjacent to the Surveillance Zone required two whole herd tests within two years for 1800 herds. Other responses to the problem have included electronic identification of all cattle in NE Michigan, and an upgrade in indemnity of to 100 percent of fair market value (to a maximum of $4,000).
By late 2003, a total of one cervid herd and 30 cattle herds had been found infected, with 28 of these located within the Surveillance or Infected zones. On two farms, reinfection of repopulated beef herds has occurred. All infected herds have been located in counties known to harbor infected free-ranging deer.
Dr. Reed E. Macarty: USDA Support of the Michigan TB Program
The United States Department of Agriculture (USDA) assists the Michigan Department of Agriculture’s (MDA) TB surveillance activities through skin testing in each of the three zones described above and slaughter surveillance (for example, 36 cases were submitted for histology and culture in 2002–all were negative). The USDA maintains a satellite office with three veterinarians and six animal health technicians in the infected area to assist with testing, herd depopulation, and research. Additional USDA staff are located in various parts of the Disease Free zone.
The USDA also assists financially through indemnity agreements, equipment and supplies, and research funding (particularly for MSU).
At the time of the workshop, the USDA was considering Michigan’s application for ‘Split State’ Status. A package sent out to other states for comment had received back 77 responses, only seven of which were unfavorable. Michigan had, at that time, achieved 97 percent completion of the statewide testing requirement.
Dr. Steven M. Schmitt: Bovine TB in Michigan’s Wildlife
Michigan has a long tradition of deer hunting, and also of recreational viewing and feeding of deer. Deer were over-harvested by the early settlers, but following the imposition of hunting regulations (seasons, bag limits) and recovery of forests after logging their populations have rebounded markedly in recent decades.
By the mid 1970s in the U.S. there had been only eight previous occurrences of bovine TB in wild deer, with only a single animal involved in each case. Consequently, when TB was first identified in Michigan deer shot by hunters (in 1975 and again in 1994) it was not initially thought that the disease would be self-sustaining in the deer population. However, the identification of numerous infected deer in the NE Lower Peninsula through surveillance efforts beginning in 1995 soon led to reevaluation of that assumption.
By mid 2003 a total of 106,028 deer (most submitted voluntarily by hunters in the fall) had been inspected, with 449 testing positive for TB. Almost all (96 percent) of the positive cases have come from the ‘four county’ area surrounding Deer Management Unit (DMU) 452. Disease appears to be spilling over into other wildlife in the area, but is unlikely be sustained in those species in the absence of ongoing infection from the deer population. (A potential exception to that would be the small herd of elk located northeast of the core area of deer infection; these elk are at risk because of their aggregated distribution and likely susceptibility to M. bovis).
Deer are thought to be contracting infection primarily by consumption of contaminated feed. There has been a long tradition of winter feeding of deer, and the majority of Michigan deer hunters will use bait to attract deer if they are permitted to do so. The bacteria can potentially survive four months or more on feed in cool conditions.