On Friday, August 15, the Montana Department of Livestock (MDOL) received confirmation that an animal from a Beaverhead County herd within Montana’s Designated Surveillance Area (DSA) tested positive for brucellosis.
According to a press release, the herd has been placed under quarantine pending the completion of an epidemiological investigation.
The positive bull was identified as a brucellosis suspect during required testing at a livestock market in late July. The animal was euthanized and taken for necropsy at the Montana Veterinary Diagnostic Laboratory where tissues were collected and sent to the USDA National Veterinary Services Laboratory (NVSL) in Ames, Iowa, for confirmatory testing. NVSL was able to grow the Brucella abortus organism from one of the lymph nodes collected from the animal.
The disease investigation will include testing and tracing of animal contacts and movements to ensure the disease is not present in other livestock herds. MDOL will work with the affected operation to minimize the impact of this diagnosis by conducting a tailored and focused investigation.
Montana’s DSA exists due to the risk of disease spillover from infected wildlife in the Greater Yellowstone Area (GYA). Program testing requirements help ensure cases of brucellosis in livestock are detected before animals leave the DSA. Successful early detection provides confidence to Montana’s trading partners that any Montana cattle they may receive are brucellosis free. Brucellosis causes reproductive issues in livestock including abortions, still births and neonatal mortalities.
“While detections of brucellosis are a hardship on operations, this detection is still a reflection of the success of our state brucellosis program,” says Dr. Brenee Peterson, MDOL veterinarian. “Through the work of DSA producers and local veterinarians, we continue to detect the disease early and prevent the export of a brucellosis-infected animal to one of our trading partners.”
Previous Brucellosis Detection
This herd is the 14th brucellosis-affected herd confirmed in Montana since the implementation of the DSA in 2010. The most recent detection was within the DSA in Madison County in April 2023. While the source of infection for this latest infected bull has not yet been determined, DNA genotyping and epidemiological investigations have concluded the previous 13 infections came from wild elk. Prior investigations have also confirmed brucellosis has not spread to neighboring herds through fence-line contact.
What is Brucellosis?
According to USDA’s Animal and Plant Health Inspection Service (AHIS) brucellosis (also known as contagious abortion or Bang’s disease) is a costly disease of livestock and wildlife. It is caused by a group of bacteria in the genus Brucella. The disease has significant consequences for animal health, public health and international trade.
Brucellosis occurs mainly in cattle, bison and swine, but can affect other animals (cervids, goats, sheep and horses) as well as people.
In cattle and bison, the bacteria of concern is Brucella abortus. It has been present in the U.S. since the 1930s. A longstanding national eradication program mostly eliminated the disease in U.S. cattle. Today, only occasional spillover cases occur in cattle and other livestock near the GYA. Wild bison and elk in the GYA are the last remaining reservoir of this disease in the U.S.
According to the APHIS website, when signs do appear, they’re most obvious in pregnant animals. Here’s what to look for:
- Abortion (usually at five to seven months of pregnancy)
- Birth of weak, unhealthy calves
- Decreased milk production
- Weight loss
- Poor conception rates or infertility
- Retained afterbirths with resulting uterine infections
- Enlarged, arthritic joints (occasionally)
“Appearance alone isn’t an effective way to detect brucellosis,” according to the website. “Infected animals may appear healthy, even during pregnancy. However, they can still harbor and spread infectious bacteria and serve as dangerous sources of infection.”
Producers or owners who suspect an animal disease should contact their veterinarian to evaluate the animal or herd.
