Ranchers could soon be spared from costly TB quarantines and culling thanks to a research breakthrough allowing the first direct, empirical, blood-based, cow-side test for diagnosing bovine TB (tuberculosis).
“We have adapted an assay originally developed for human TB to bovine TB, a particular challenge because the bovine disease is caused by a different species of the pathogen,” said Harshini Mukundan, leader of the Chemistry for Biomedical Applications team at Los Alamos National Laboratory that developed the assay and corresponding author on the study, published in the journal Analytical Sciences. “We have validated the assay in cows that were positive controls of a vaccination study done at the US Department of Agriculture, tested at different time points during the course of infection. This work supports the global One Health strategy — developing diagnostics that are not host limited.”
TB is one of the oldest known diseases, and it infects both animals and humans. In cattle, Mycobacterium bovis causes the disease, which easily spreads among large herds, periodically resulting in the quarantine and destruction of thousands of cattle in the United States, Canada, and abroad, and restricting international shipments. It also infects wild deer and elk, which can pass it on to domestic cattle with which they graze. A skin test to detect exposure or infection is used in cattle, but due to various colors of cows’ skin and hide, environmental exposures, previous testing for M. bovis and other factors, the visual assessment can be inconclusive. Further, Mukundan notes, gathering a herd once for testing and then again 48 hours later for reading the skin results can be a challenge in itself.
To detect it, the Los Alamos team has developed a novel assay – lipoprotein capture – which exploits the interaction of LAM with host lipoproteins and can thereby detect it in blood. Combined with a highly sensitive waveguide-based optical biosensor for the rapid, sensitive, and specific detection of pathogenic biomarkers, the team has effectively identified greasy biomarkers associated with diseases like tuberculosis, food poisoning, leprosy, and others.
In cattle, the TB infection M. bovis secretes a similar biomarker called lipomannan (LM). The team adapted the human assay to target LM, thereby suggesting the possibility of a molecular cow-side test for bovine TB.
“We are hoping to work with the New Mexico Livestock Board and the USDA to evaluate infected animals in the real world,” Mukundan said. “It will be wonderful if the assay can be adapted to a rapid cow-side test that can be used by ranchers and farmers to effectively diagnose bovine TB. I am especially interested in providing something concrete to farmers and veterinarians in our state, the New Mexico Livestock Board and the USDA, all of whom require such a test.”