A new screening tool developed by researchers at Iowa State University and the U.S. Department of Agriculture can dramatically reduce the time to detect strains of Mycobacterium bovis, the bacteria that causes bovine tuberculosis (TB), a serious livestock disease that affects the health of millions of animals and people worldwide.
Bovine TB is a zoonotic disease — one capable of being transmitted from animals to humans, Iowa State said. The pathogen, M. bovis, is closely related to the one causing human tuberculosis (Mycobacterium tuberculosis).
The new tool collects extremely low levels of volatile organic compounds emitted by the bacteria, making it possible to differentiate between disease-causing and non-disease-causing strains of Mycobacteria, Jacek Koziel, professor of agricultural and biosystems engineering, said. The device can be used to collect and analyze samples within hours -- much more quickly than current methods, which often take up to eight weeks, the university said in an announcement.
In addition to speeding up identification, the new testing platform is also portable and less expensive than tools typically used to test for bovine TB in the laboratory, according to the announcement.
Bovine TB causes coughing and lung damage, often leading to death. It primarily affects cattle and white-tailed deer in the U.S. and can be transmitted to people who come in contact with infected animals and their meat or hides or unpasteurized dairy products. Other mammals, including bison, elk and feral and domesticated swine, are susceptible, Iowa State said.
While human TB is generally linked to M. tuberculosis, about 30% of human cases worldwide — out of an estimated 9.6 million total new cases (in 2014) — are linked to bovine TB. These cases represent an estimated 200-300 human TB cases annually in the U.S. and millions in developing countries where the disease is more prevalent in cattle.
Bovine TB often goes underreported and can spread widely. The course of the disease is slow, and a sick animal can infect others before symptoms start to show, Iowa State said. Disease transmission can also occur during the long incubation time current testing procedures require to culture and identify the bacteria.
“That’s why the speed of the new lab-scale method is so valuable,” Koziel said. “This is an important step towards an accurate, real-time screening device for these diseases.”
The new tool uses a biosecure, closed-loop circulating airflow system to collect the volatile organic compounds from growing bacteria in lab cultures. The collected samples are then analyzed using detailed statistics and other methods to identify the unique signature of gases different microbes emit over time.
“This ability to detect the evolution of disease ‘fingerprint’ volatiles is something that current methods cannot provide,” Koziel added.
“The tool was developed with many materials we had on hand, with support from collaborators who believed in the idea and knew it could be an important advance,” he said.
Koziel worked with Devin Maurer, an Iowa State research associate in agricultural and biosystems engineering who now works in the industry. They collaborated with Christine Ellis, who was a research fellow with the USDA Animal & Plant Health Inspection Service's National Wildlife Research Center in Ft. Collins, Colo., and Tyler Thacker, a research microbiologist affiliated with the USDA Agricultural Research Service's National Animal Disease Center in Ames, Iowa.
“I hope this leads to more in-the-field, quicker response screening tools to help control the spread of livestock disease,” Maurer said. “It also has potential to be adapted to help diagnose other diseases — and even to fingerprint environmental, forensic or pharmaceutical specimens that you might want to limit direct contact with.”
The tool is not yet ready for widespread use, but Koziel expects that it could soon become part of a standardized test. To take it to the next step, he said, “additional side-by-side crosscheck testing with ‘gold-standard’ current methods is still needed.”
Research findings on the new sampling tool were featured in the August issue of Scientific Reports.
The new disease screening tool was also featured in Koziel's presentation at the recent International Conference on Sustainable Animal Husbandry in Poland.