New studies shed light on how TB and Ebola spread from animals to people

Several of the world's most vexing diseases can be spread from animals to people, including tuberculosis and Ebola virus. But figuring out just how the transmission happens--and how it can be stopped--has been challenging. Two studies released in December could help world health authorities get a better handle on TB and Ebola.

At the World Conference on Lung Health in South Africa, held in early December, the U.S. Centers for Disease Control and Prevention (CDC) presented new data showing that 230 cases of TB diagnosed in the U.S. each year are the bovine form of the disease, which spreads from cattle to people largely via unpasteurized milk products. Cases of bovine TB are most prevalent in Hispanic communities, where consumption of raw cheese is common.

Screening programs are in place to control TB infections in commercial cattle, but they're typically not used on small dairy farms, according to public health experts interviewed by CNN.com. And the problem is even worse overseas, where more than 7% of livestock have tested positive for the disease, according to data collected by CNN. Screening programs for people often don't detect bovine TB, and efforts are now underway to determine to what degree the disease can be passed among people.

As for Ebola, it has long been known to be harbored by bats, but exactly how the virus caused last year's epidemic in West Africa is still not well understood. On December 23, a team of researchers led by the Albert Einstein College of Medicine in New York released a study suggesting that the epidemic was probably not caused by a commonly cited culprit: the African straw-colored fruit bat. That's because that particular species of bat harbors cells in its body that resist Ebola infection, unlike the three other bat species they studied.

The findings, published in the journal eLife, reveal that a tiny change in a gene called NPC1 prevents Ebola from taking hold in some bats. Their data suggests that bats and Ebola have coexisted for more than 25 million years, and that the virus is evolving over time to dodge the critters' resistance to the disease.

"Identifying potential animal reservoir hosts for Ebola virus will provide a crucial guide for public health prevention and response programs going forward," said John Dye, viral immunology branch chief at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID), in a press release. USAMRIID scientists participated in the study.

Unlocking the mysteries of diseases that can be transmitted from animals to people is a priority for advocates of the growing movement known as One Health. The goal of One Health is to foster research collaborations between human health and animal health experts aimed at eradicating diseases that affect many species. An estimated 60% of infectious diseases originate in animals and 75% of emerging human illnesses are believed to be transmitted from animals, according to data presented early last year at the One Health Congress.

- read more about cows and TB at CNN.com
- here's the press release about the Ebola study 
- access the eLife study here

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