A new bovine TB roadmap

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For nearly 100 years, the United States has been on a mission to eradicate bovine tuberculosis. The Cooperative State-Federal Tuberculosis Eradication Program, administered by USDA’s Animal and Plant Health Inspection Service (APHIS), began in 1917. While quite successful in terms of reducing overall disease prevalence and impact, the program is showing its age.

For instance, farmers and animal-health officials alike are frustrated by its inflexibility to adapt to current livestock practices and industry technology. But, then, not many people had heard of commuter dairy herds (animals that move interstate without changing ownership) in 1917. These facts, combined with fiscal realities, mean the time is ripe to rework bovine TB policies.

Following a series of listening sessions held throughout the country last December, APHIS and industry stakeholders are in the midst of modernizing the eradication program to increase responsiveness and effectiveness, while taking advantage of new technologies and management strategies.

Here’s the latest information on what’s happening with this disease and eradication efforts.

Q: In which states is bovine TB found?

A: At one time or another, every state has been declared TB-free. However, several states have been unable to maintain that status. And others have had a single bovine TB-affected herd, which does not necessarily affect their bovine TB-free status, provided the herd is depopulated and a second case is not confirmed within four years of the initial case. (For more on the state status system, go to: www.dairyherd.com/health)

According to Bill Hench, senior staff veterinarian with APHIS Veterinary Services, from fiscal year 2005 through fiscal year 2009, 11 states have had at least one confirmed TB-affected herd of either cattle or captive cervids (deer or elk). These states include Arizona, California, Colorado, Indiana, Michigan, Minnesota, Nebraska, New Mexico, New York, Oklahoma and Texas.

Q: Is the disease spreading?

A: Comparatively speaking, not so much. Bovine TB slaughter surveillance by USDA Food Safety and Inspection Service personnel has increased each year over the last decade, which probably contributes to some of the rise in cases.

But keep in mind, bovine TB was once the most prevalent infectious disease of cattle and swine in the United States. The disease caused more losses among U.S. farm animals in the early part of 1900s than all other infectious diseases combined.

That said, the disease has obviously not been eradicated. DNA-genotyping of bacteria from confirmed cases enable investigators to determine most infection sources, many of which are regional or state-specific in origin.

However, widespread animal movement and inconsistent biosecurity practices complicate the picture. It’s not unheard of for an adult dairy cow to move as many as seven or more times in her life. Nor is it impossible for animals to contract the disease from workers who come from countries where the disease is still a problem. All of which confirm the need to remain vigilant, and modernize the program.

Q: What challenges face the eradication program?

A: As previously mentioned, the program originated in different times and has not kept up with changes in livestock production. This is the main sticking point for those who must deal with the process it outlines — both herd owners and animal-health officials.

For example, Richard Breitmeyer, California State Veterinarian, calls for great flexibility in program rules, primarily to address bovine TB on a herd-by-herd basis, rather than penalizing an entire state with the cost of unnecessary testing and movement restrictions. He adds that lack of animal identification and recordkeeping added to workloads and, in some cases, prevented successful tracing of animal movement during the state’s latest investigations.

The need for increased program flexibility is echoed by Minnesota State Veterinarian William Hartmann. “In Minnesota’s four-year battle with the disease,” he says, “it has become apparent that the current program rules were more useful in the initial eradication effort (of 30 years ago) than they were for the reintroduction of the disease (in 2005). Hartmann notes that investigators had to expend efforts in areas of the state with little chance of disease during the investigation, rather than focus all of their efforts on areas with significantly higher odds of disease in order to satisfy existing program rules.

“Of particular note is the state-status system, which is outdated, cumbersome and leads to waste of valuable resources,” he adds. “We have learned that under the current system, the last thing you want is for your cattle to get bovine TB.”

Finally, Steve Halstead, Michigan State Veterinarian, says that more than $100 million in state and federal funds have been spent over the past 10 years to keep the disease contained in a corner of the Michigan’s Lower Peninsula. Mandatory testing, electronic identification for cattle, movement permitting and controls, along with aggressive animal management have been successful, but have taken their toll on farmers.

“The cash, lead-time, productivity and marketability cost of testing, electronic ID, movement restrictions and on-going wildlife-associated disease risk have made producers more fearful of the program than of the disease itself,” he says.

Q: What changes have been proposed to the program?

A: In late July, John Clifford, deputy administrator for APHIS Veterinary Services, released a draft copy of proposed changes to attendees of a meeting designed to address the future of the national bovine-TB program.

The meeting was sponsored by the United States Animal Health Association and featured the first public look at “A New Approach for Managing Bovine Tuberculosis: Veterinary Services’ Proposed Action Plan.”

In a nutshell, the action plan intends to accomplish five things:

  • Reduce the introduction of bovine TB to the U.S. national cattle herd from imported animals, as well as wildlife sources. Under this strategy, additional testing and/or identification requirements will be placed on Mexican cattle imports. It will also enhance efforts to mitigate risks from wildlife — via the use of farm-specific plans like those under way in Michigan.
  • Enhance bovine TB surveillance efforts. This involves crafting a national surveillance plan and accelerating diagnostic test development to support surveillance.
  • Increase management options for TB-affected herds. This means epidemiological investigations (studies that confirm the case, determine the source, conduct disease surveillance and traceback and then offer prevention and control strategies while monitoring responses to intervention) and individual herd-risk assessments will be conducted. Whole-herd depopulation will be applied judiciously, and alternative control strategies will be developed. This step would require the application of official animal ID to all cattle, as well as traceability standards.
  • Modernize the regulatory framework to allow APHIS Veterinary Services to focus resources where the disease exists.
  • Transition the state classification system to a science-based zoning approach to address disease risk.

Go to www.dairyherd.com/health to access the proposed action plan for more information on each of these steps.

Q: What happens next?

A: The proposed plan has been posted online for all to see. And USDA is accepting public comments on any and all aspects of it until Dec. 4.

“We strongly encourage people to comment,” says Hench. “We really want to hear from those impacted the most.”

Once the public comment period has closed, USDA will review all input received on the proposed changes, including that from the listening sessions and all feedback opportunities. This information will then be used to formulate the revised plan.


What is bovine tuberculosis?

According to USDA, bovine tuberculosis (TB) is a chronic, contagious bacterial disease caused by Mycobacterium bovis, a bacterium that usually affects the respiratory system. Clinical symptoms are difficult to observe in the disease’s early stages. But, in later stages, clinical signs include emaciation, lethargy, weakness, anorexia, low-grade fever, and pneumonia with a chronic, moist cough. Lymph nodes may also be enlarged.

It is of significant concern because it is zoonotic, which means it can be transmitted from livestock to humans and other animals (and vice versa). No other mycobacterial organism has as great a host range as the one that causes bovine TB, which can infect most warm-blooded vertebrates.


Resource corner

For more information about bovine tuberculosis, to learn more about the proposed national eradication program changes or to comment on the proposed changes, go to: www.dairyherd.com/health.

 



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