TB Testing Makes More Sense In Some Countries Than Others

“We are committed to eradicating the disease, and believe it can be done.”

– DR. MARI A KOLLER-JONES

Battle-fatigued ranchers on the front lines of the fight against bovine tuberculosis near Riding Mountain National Park aren’t alone in questioning whether ongoing eradication efforts are worth it.

Dr. Paul Torgerson, a U. K.-born veterinarian who tested thousands of cattle two decades ago in Britain’s fight against the disease, has published an opinion piece in the February issue of Trends in Microbiology arguing that from a public health perspective, the U. K.’s current TB strategy of widespread testing and culling of infected herds at a cost of C$200 million per year is a “misallocation of resources.”

Canadian officials caution, however, that the TB situation in Britain differs from Canada where testing affects only a small part of an industry that is heavily dependent on access to export markets.

The published article represents only Torgerson’s opinion, not peer-reviewed science, said Dr. Maria Koller-Jones, the vet who heads the CFIA’s TB-testing program.

“It’s an opinion that’s not shared by public health authorities around the world, starting with the World Health Organization on down,” said Koller-Jones.

In a telephone interview last week, Torgerson, who is now a veterinary epidemiology professor at the University of Zurich, concedes the article he co-wrote with his brother David, a professor of public health economics at the U. K.’s University of York, caused “a bit of a stir” in veterinary and academic research circles.

CONTROVERSIAL VIEW

Torgerson believes that the 50-year war on TB in the U. K. can never be won, and argues that the problem there is in fact getting worse.

If meat is inspected, and milk pasteurized, he said, the only remaining vector of transmission to humans is aerosol from animals coughing or breathing on the farmer, which his research shows represents a negligible risk.

In the past 40 years, there have been only one or two cases of farmers catching TB from their animals via aerosol transmission. Farmers are more likely to be trampled to death while mustering animals for testing, he said.

So why test?

“Basically, it’s a waste of money,” said Torgerson. “It’s really not working very well, it’s gotten heavily politicized, and the large amounts of money used are making no positive contribution to public health.”

Under the UK system, every herd must be tested, even though exports of live animals represent just 1.6 per cent of all production. Farms with positive reactors are “frozen” in quarantine until they test free of the disease, causing economic hardship for farmers.

INFECTED IMPORTS?

At the same time, he added, the country continues to import beef from South American countries where TB is endemic with no control programs. In most countries, even if a slaughtered animal is found to be positive at the killing plant, the infected lesions are simply trimmed off and the rest of the carcass approved for human consumption.

Efforts to control badgers, which serve as an uncontrolled and widespread reservoir of bovine TB, have been stymied by nature lovers.

If a country’s bovine TB eradication efforts were abandoned, rates of the disease would soar to 19th century levels, he admitted. However, very little data exists on the actual economic impact on beef and dairy production.

“Nobody knows what the direct costs of the disease are,” he said. “But we do know the direct costs of the program.”

He suggests freeing farmers to choose their own control measures, such as strictly monitoring new animals brought into the farm, applying poultry or pork-style biosecurity measures, more aggressive culling of older or sick animals, or vaccinating calves with Bacillus Calmette-Guerin, or BCG.

Currently, the vaccine, which is 60 to 70 per cent

effective in preventing TB if given to young calves, is not allowed in most countries because it causes animals to react to the caudal fold screening test.

“Those who gain from exporting live animals could have their own scheme and leave the rest of the farmers to get on with it,” he said.

HARDSHIP FOR PRODUCERS

“The problem is that the farmers think it’s the disease that’s costing them money. It’s not. It’s the control program that costs them money,” he said. “Maybe if the farmers realized this, there might be more resistance to having this program thrust upon them.”

However, Ko l l e r-Jones, said that the situation in the U. K. is “totally different” from Canada, where the cost of testing in the RMEA is $250,000 per year.

Unlike Canada, which is 99 per cent TB free, the U. K. is dealing with a “mammoth” bovine TB problem believed to be spread by badgers. “Even their urine is infected. That’s something that we don’t see with the wildlife reservoirs here,” she said.

The other significant difference is Canada’s cattle industry is largely dependent on exports of live animals to the United States.

“Living with TB may be an option for the U. K. in a cost-benefit model, but for Canada, it would look totally different,” she said, adding that most of the work of eliminating TB has already been done over the past century, and only a few dwindling pockets remain.

In the real world, trade barriers are thrown up for the slightest excuse, and international standards demand TB-free status, she said.

ERADICATION WITHIN REACH

Demand for unpasteurized milk and cheese is growing as part of the local food movement, and if bovine TB was more common, more people could become infected and possibly die from consuming such products.

“Once it’s in the human population, it can spread very efficiently from human to human,” said Koller-Jones.

The BCG vaccine is given to children in countries where TB is endemic and it has been shown to be effective. In cattle, however, it is only appropriate to use it as a means of reducing the prevalence and burden of the disease, not in countries where TB is rare.

“If you asked the cattle industry if they’d like to start vaccinating for a disease where the prevalence is less than 0.01 per cent of the cattle population and make those cattle ineligible for export – I don’t think they’d go for that,” she said.

“I understand that producers get frustrated and wonder where’s the light at the end of the tunnel,” she said. “We are committed to eradicating the disease, and believe it can be done.” [email protected]

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