At 6:00 every morning, 200 cows line up one behind the other at a slaughter house in Zapopan, in the Mexican state of Jalisco. Unlike pigs, which screech before they're killed, the cows are silent, seemingly unaware they're about to be slaughtered.
The cows are killed using a gun that hangs from the ceiling before they are hung up, skinned, and pulled apart by workers using a chainsaw. The slaughter house room looks like a murder scene: white ceilings and walls sprayed with blood, workers' uniforms—and their hands— stained red. The stench is overwhelming.
A few of the workers are vets, tasked with the vital job of checking the cows for bovine tuberculosis (TB). Unlike the TB we're familiar with, which spreads from human to human when a person infected coughs, speaks, or sings, bovine TB is spread from animals to humans usually through unpasteurized milk, raw or uncooked meat, and direct contact with infected animals. This type of tuberculosis is called zoonotic TB, which is most commonly spread to humans from livestock. Every cow that is trucked in from ranches across Jalisco is checked ante-mortem for injuries, then post-mortem for lesions on their organs, such as the lymph nodes. If any are found, a sample must then be taken to a laboratory to confirm whether the lesion is TB. It's an arduous process, but one that's vital to ensure that infected meat isn't passed into the food chain.
But as veterinarian and slaughter house manager Brigida Espinoza explains, confirmation of TB among livestock is devastating for farmers, whose livelihoods depend on selling the meat to butchers and markets. "If cows are confirmed to have TB," Espinoza says, "they will lose 80 percent of their income."
Last year, 147,000 people were infected with zoonotic TB and 12,5000 died, according to the World Health Organization. While the figures are small compared to the more than 10 million cases of human TB and 1.8 million deaths recorded every year, experts agree that if the global goal of ending the TB epidemic by 2035 is to be achieved, then every case counts.
But a major problem with zoonotic TB is that few people in the areas that are most affected by the disease—sub-Saharan Africa and South Asia—know about it or how it's spread. Moreover, many countries don't have policies in place to screen animals for disease or inspect meat for contamination, says Simeon Cadmus, a zoonotic TB expert and professor of veterinary medicine at the University of Ibadan in Nigeria.
"Poverty and ignorance allows this to go on," Cadmus says. "This is a big problem in settings where the animal welfare system is broken and where there are no vets and poor sanitation."
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In 2011, Timpiyian Leseni from Kajiado—50 miles from Kenya's capital of Nairobi—noticed her stomach was increasing in size every day. Then came the vomiting, night sweats, and rapid weight loss—her weight fell to just 80 pounds. She was 36 years old.
"It hit a point when I couldn't go to the toilet. The pus had blocked my anus. Nothing was coming out. I was so weak and thin," she says. Leseni wound up hospitalized in Nairobi, where doctors operated on her to remove the masses that had formed in her stomach.
"The doctor told me it was TB, that I had TB of the stomach. It was the type you get from drinking milk that hasn't been boiled or meat that hasn't been cooked properly," Leseni says. She was startled.
Leseni is from the Maasai tribe, a unique tribe from southern Kenya and northern Tanzania, which, despite globalization and western cultural influences, have clung to their traditional way of life. For the Maasais, that means eating rare goat and beef and drinking goats' blood.
"Here I was sucking blood from the goat. We were brought up doing that, it's part of our stable diet," she says. After doctors removed the pus from Leseni's stomach, she was put on anti-TB drugs for six months. When she went back to her community—she wanted to educate people about the dangers of drinking animal blood and eating uncooked meat—they resisted; they wouldn't take her seriously.
"How can I tell them that what they've been eating since they were alive could be infected with TB?" she says. But eventually, her awareness-raising started having an impact: More and more people came forward explaining that they'd lost loved ones that had experienced the same symptoms as her. Word spread in the community, and Leseni began educating people about how to prevent TB infection through TALAKU, a community-based organization that she founded.
"People used to think you would get TB from sharing plates or cups. They didn't know it was airborne or could spread from animals," she says. "But now I'm seeing changes in the community, where people are more accepting and people are making changes in their lives to reduce the risk of TB."
Experts recognize that Mexico is a shining example of what needs to be done to prevent TB spread from animals to humans. But in less developed regions, there's a long way to go. Experts want countries around the world to improve their national food safety standards, and they also want an effective TB vaccine for livestock and people. But only time will tell whether these goals will ever be realized.
"TB is the top infectious disease killer today," says Monica Dias, information and technical officer for the World Health Organization. "But while there has been progress in combating TB, efforts to address zoonotic TB are really lacking behind."
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