Salmonella Dublin test for blood or milk samples from cattle

Monday, May 21, 2018

Salmonella can cause serious disease on cattle farms, killing calves, causing cows to abort, contaminating raw milk, and harming humans along the way. While the cattle-adapted strain Salmonella Dublin creeps into the Northeastern US, 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.

A useful test for Salmonella Dublin is available at the Cornell University College of Veterinary Medicine’s Animal Health Diagnostic Center (AHDC). Cheaper, quicker, safer, and more sensitive that fecal culture for detection of animals that have been infected, the test detects antibodies rather than bacteria. Traditional bacteriological tests could only identify Salmonella Dublin organisms in sick or deceased animals, missing up to 85% of infections in carrier cattle. The new test can be used sequentially to identify carriers, helping farmers and health professionals monitor infection spread over time and track the impact of control measures in ways that were previously impossible.

“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 Dr. Belinda Thompson, senior extension associate at the AHDC. “Salmonella Dublin is already common in the western United States, but it’s only recently being recognized in the Northeastern US. We want to be pro-active now to keep it out of our farms.”

In recent years the AHDC 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, Dr. 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.

While Salmonella Dublin usually doesn’t make adults cows very sick, 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, to make matters even worse, it often presents as respiratory disease, throwing off track veterinarians trained to recognize diarrhea as Salmonella’s telltale sign.

People working with cattle are also at risk. All Salmonella strains affect most 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 availability, culture 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 farmers are considering buying.

Veterinarians can contact Dr. Belinda Thompson to discuss the test and issues surrounding Salmonella Dublin management and control.

Dr. Thompson: bt42@cornell.edu               607-253-3908

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