A test for the cattle disease salmonella dublin that is cheaper, quicker, safer and more sensitive than traditional bacteriological tests is now available for the first time in the United States at the NYS Animal Health Diagnostic Center at Cornell University’s College of Veterinary Medicine.
The new test detects antibodies rather than bacteria. Traditional bacteriological tests identified only the bacteria in sick or deceased animals, missing up to 85 percent of infections in carrier cattle. The new test reveals carriers, helping farmers and veterinarians monitor infection spread over time and track the impact of control measures.
Salmonella can cause serious disease on cattle farms, killing calves, causing cows to abort, contaminating raw milk and harming humans along the way. As the cattle-adapted strain salmonella dublin creeps into the northeastern United States, veterinarians and farmers struggle to catch the bacteria in time to protect livestock because these bacteria often hide dormant in carrier animals, making the strain particularly hard to diagnose.
“We're very concerned about this disease spreading east because it could severely harm animal and human health, as well as the livelihoods of dairies in the region,” said Belinda Thompson, senior extension associate at Cornell’s Animal Health Diagnostic Center. “Salmonella dublin is already common west of the Mississippi River, but it's only recently being recognized in the northeastern U.S. We want to be proactive now to keep it out of our farms.”
In recent years, Cornell’s diagnostic center has dealt with several high-morbidity and high-mortality outbreaks of salmonella dublin in New York and other states. To address the problem before it grows further, Bettina Wagner, director of the Serology and Immunology Section of the AHDC laboratory, secured the nation's first USDA permit to import and use the enhanced test.
Salmonella dublin usually doesn't make adult cows very sick, but it can wreak havoc on young and unborn calves, particularly in populations like those in the East Coast that haven't been exposed. Its resistance to many common antibiotics severely limits treatment options and often presents itself as respiratory disease, throwing off track veterinarians trained to recognize diarrhea as salmonella's telltale sign.
All salmonella strains affect humans and most other vertebrates and can jump between species. Even carriers that don't seem sick can shed bacteria, and people, companion animals and other livestock can pick up the infection through contact with any bodily excretion.
Prior to the new test's release, testing had to be done animal by animal. The new antibody test can use milk samples straight from bulk milk tanks to find whether a herd has been exposed. It can also work with blood samples and diagnose individuals, helping keep unexposed herds infection-free by removing infected animals and pre-screening new animals that farmers are considering buying.
“Herd managers can take preventative measures and help control the infection's spread by isolating sick calves, pasteurizing milk, managing cattle movement and improving hygiene,” said Thompson. “But to see if any of this is working, they need a tool to monitor success. We didn't have that until now. This test will let us learn about the prevalence of salmonella dublin on the East Coast and hopefully nip it in the bud.”