CORVALLIS - With the help of DNA technology, animal science researchers at Oregon State University have developed, and recently submitted a patent for, a diagnostic test for detection of a deadly disease responsible for killing growing numbers of cows in dairy herds throughout the United States.
Hemorrhagic Bowel Syndrome (HBS), also known as dead-gut, causes blood clotting in the small intestines that obstructs and enlarges the bowel in dairy cows, causing the animals to suffer severe distress and, in many cases, sudden death.
The disease was identified in 1991 as a significant and growing problem for the dairy industry.
OSU animal scientist Neil Forsberg and graduate student Steve Puntenney developed the diagnostic test during their studies of a feed additive (OmniGen-AF) devised by Puntenney to combat the disease.
The test employs a DNA technology tool called polymerase chain reaction (PCR) to analyze blood and tissue samples for presence of DNA of the common mold Aspergillus fumigatus, which is widely thought to cause HBS in dairy cows.
The PCR process is used to copy and reproduce a specific fragment of DNA, which allows scientists to multiply tiny amounts of DNA material so it can be studied and quantified more precisely.
According to Forsberg, the test is currently the only quantitative means available to the U.S. dairy industry for detection of Aspergillus contamination. He and Puntenney submitted a patent on the process through the OSU Office of Technology Transfer earlier this year.
The test is now available to producers through an Aspergillus diagnostic lab in the OSU Animal Sciences Department, which operates on a fee-per-sample basis. Forsberg and Puntenney began their joint research on HBS as a result of Puntenney's earlier work on the disease.
"Steve has worked in the dairy industry as a nutritional consultant for many years and was aware of increasing problems with HBS and efforts to diagnose and control the disease," Forsberg explained. "Initially, many within the industry believed the cause of HBS was Clostridium perfringens bacteria, which are everywhere in the environment and a common cause of intestinal disease problems in both humans and animals."
But Puntenney had a different theory about the cause of dead-gut after seeing cows tested for bacterial infections.
"I suspected A. fumigatus mold might be the cause after observing many efforts to help sick cows by treating them for C. perfringens infections," said Puntenney. "That approach didn't work.
"The mold A. fumigatus is similar to C. perfringens - it is common in the environment and known to cause intestinal problems in humans and animals - so I developed a feed additive for dairy cows designed to eliminate the mold, and it was effective," Puntenney said.
This feed additive is now marketed nationally and is entering international markets. Presently, about 500,000 cows receive the additive daily.
Forsberg and Puntenney initiated their study to find out why the feed additive worked so well. In the process, they found that HBS is associated with A. fumigatus mold. Their finding later received additional support from research at Michigan State University on the causes of HBS.
Reports of HBS in the U.S. dairy industry have surfaced at various times for years, but the number of HBS cases has increased dramatically over the past decade, according to Puntenney.
Forsberg believes the expansion of the disease may be due to stressed immune systems in dairy cows.
"In situations where producers manage their dairy herds to get as much milk production as possible, cows may suffer physical and metabolic stress, which weakens their immune systems making them more susceptible to disease," said Forsberg.
He added that a source of the mold is likely dairy feed that becomes wet due to exposure to rain or snowfall.
"Given the right temperature and access to air, mold will grow rapidly on moist dairy feed material," said Forsberg. "Keeping feeds dry and sealed from air may be an important factor in controlling HBS."