Brucellosis Found in Montana Cattle Herd

January 6, 2022

The Montana Department of Livestock received notice that an animal from a Madison County herd located within Montana’s brucellosis Designated Surveillance Area (DSA) has been confirmed positive for brucellosis.

The positive animal tested as a ‘suspect’ on a whole herd test conducted in December 2021. Pathologists at the Montana Veterinary Diagnostic Laboratory collected tissues and forwarded the samples to the National Veterinary Services Laboratories in Ames, Iowa where infection was subsequently confirmed. The ranch has been placed under quarantine and an epidemiological investigation has begun. The positive animal tested negative the prior year, which allows the Department to reduce the scope of the disease investigation.

Voluntary whole herd testing is an effective method for DSA producers to protect their herd. Early detection of infections not only allows producers to detect the disease before it spreads within the herd, but it also minimizes the time required to clean up a herd, and thereby shortens the duration of quarantine which allows herd owners to control when testing happens, often by pairing with other ranch management activities.

“A high rate of testing, much of it voluntary, is the primary reason we continue to find affected herds rapidly,” said State Veterinarian Dr. Marty Zaluski. “A robust testing program minimizes the impact to that operation and protects our state and trading partners,” Dr. Zaluski said and commended Montana DSA producers for their high rate of compliance with brucellosis testing regulations.

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 source of infection in the Madison County herd has not yet been determined.

This is the 11th brucellosis affected herd detected since the creation of Montana’s DSA in 2010. Prior to the creation of 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. Currently, brucellosis-affected herds are not subject to depopulation if cases are found within a DSA and states can maintain their Class Status.

Source: Montana Department of Livestock