Chinese scientists have developed a genetic engineering technique using a mouse gene that makes cattle much more resistant to tuberculosis. They believe their study will help reduce the number of culls of infected herds, as well as doing away with the blanket use of antibiotics.
The scientists, Haibo Wu, Yongsheng Wang, Yan Zhang, Mingqi Yang, Jiaxing Lv, Jun Liu, and Yong Zhang, from Northwest A&F University in Yangling, China, published their findings in the academic journal Proceedings of the National Academy of Sciences (citation below).
They say their study is the first to show that when cattle carry the modified mouse gene, they become much more resistance to bovine tuberculosis (TB).
Genetically modified cattle are more resistant to bovine tuberculosis.
Bovine TB is a chronic infectious disease that affects a wide range of mammals. It is a serious threat to agriculture in several less-developed nations, the authors explain. Many advanced economies are also concerned about the potential damage of bovine TB.
Professor Bruce Whitelaw, Deputy Director of the Roslin Institute at the University of Edinburgh, said:
“The world faces unprecedented population growth on a backdrop of competing pressure on agricultural land and resources. Society needs to embrace many strategies to address this global challenge, both traditional and new, with many seeing genetic engineering as contributing to the much needed solutions.”
The researchers created twenty-three genetically modified calves using a gene-editing tool called TALEN, which allows them to delete naturally occurring genes and insert new ones. The animals had been given a mouse gene known to be protective against TB. Thirteen of the calves survived into adulthood.
Mouse gene provides significant protection
Laboratory tests showed that the TB-causing bacterium, Mycobacterium bovis, multiplied in far smaller numbers in the presence of the immune cells taken from the genetically modified cattle.
They compared three genetically modified (GM) cattle with three control animals (non-GM) after introducing TB bacteria into their lungs. One of the GM cattle was completely disease-free, i.e. it showed no signs of illness, while the other two GM animals had significantly fewer lesions than the controls in the liver, spleen and lungs.
In another test, they housed nine GM cows and nine controls with infected animals. Six GM cows remained infection-free, while the other three again showed considerably fewer symptoms compared to all nine controls.
Scientists worldwide are encouraged by the results. While not providing total TB resistance in cattle, it does significantly slow down the spread of the disease, which would mean far fewer herd cullings.
The authors concluded in an Abstract in the journal:
“Our results contribute to the control and prevention of bovine tuberculosis and provide a previously unidentified insight into breeding animals for disease resistance.”
About bovine TB
During the first half of the last century, bovine TB is estimated to have caused more losses among farm animals than all other infectious diseases combined.
Mycobacterium bovis can be transmitted to humans via infected milk. Human infections today are rare, mainly because most milk is pasteurized.
In areas of the world where pasteurization is not routine, the M. bovis is a comparatively common cause of human TB.
Bovine TB can affect a broad range of mammals, including cattle, wild carnivores (coyotes, foxes), cats, pigs, llamas, deer, omnivores (rodents, possums), and humans. It very rarely affects sheep.
Citation: “TALE nickase-mediated SP110 knockin endows cattle with increased resistance to tuberculosis,” Haibo Wu, Yongsheng Wang, Yan Zhang, Mingqi Yang, Jiaxing Lv, Jun Liu, and Yong Zhang. Proceedings of the National Academy of Sciences. Published online before print March 2, 2015. DOI: 10.1073/pnas.1421587112.