The Montana Department of Livestock reported Dec. 30 that a single cow on a Madison County, Mont., ranch within Montana’s brucellosis Designated Surveillance Area (DSA) has been confirmed positive for brucellosis.

The brucellosis-infected cow was identified during a voluntary whole-herd test, the agency said. The animal was euthanized, and infection was subsequently confirmed at the National Veterinary Services Laboratories in Ames, Iowa, when the bacteria was cultured from tissue collected from the animal.

The ranch has been placed under quarantine, and an epidemiological investigation has begun. All other animals on the ranch tested negative for the disease, the agency said.

Montana state veterinarian Dr. Marty Zaluski said the discovery of the single animal provides evidence that annual whole herd testing is an effective method for DSA producers to protect themselves. Among other benefits, early detection helps prevent disease spread within a herd, minimizing the time needed to clean up a herd and remove quarantine. The positive animal had tested negative the prior year.

“It can be concerning when a brucellosis-affected herd is discovered, but our DSA producers and veterinarians should be commended for their efforts and compliance with regulations,” Zaluski said. “A high rate of testing -- much of it voluntary -- is the primary reason we continue to find affected herds rapidly, which not only minimizes the impact on that producer but protects our state and our trading partners.”

Past cases of brucellosis in livestock were the result of transmission from infected wild elk, as determined by an epidemiological investigation that included genetic fingerprinting (genotyping) of the cultured bacteria, the agency reported.

This is the 10th brucellosis-affected herd found since the creation of the DSA in 2010. Prior to the DSA, if two or more affected herds were detected in a two-year period, the state would have lost its brucellosis class-free status. Due to the current U.S. Department of Agriculture regulations and Montana’s DSA, Montana is not at risk of dropping in class status, the agency explained.

The mission of the Montana Department of Livestock is to control and eradicate animal diseases, prevent the transmission of animal diseases to humans and protect the livestock industry from theft and predatory animals.

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