Laboratory results confirmed the disease in a single herd Aug. 24, near Raymond, Mont. Local and state animal health officials have visited the location and have taken appropriate measures to prevent further spread of the disease. 

Field investigations indicate this was a naturally occurring case of anthrax and has been limited to one ranch. Neighboring ranches have been notified.

Anthrax is a disease caused by the bacterium Bacillus anthracis, and the organism naturally occurs in the soil of many western states, including Montana. The organism forms spores which can survive in the soil for decades. Typically, the disease in livestock and wildlife appears following periods of climatic or ecologic changes, such as heavy rains or flooding preceded by drought, although they may also be exposed by wind or water erosion.  These factors make it possible for an outbreak to occur one year, but not the next. 

The last reported case of naturally occurring anthrax in livestock in Montana was reported in 2005 in RooseveltCounty, and before that, two unrelated cases in 1999, one occurring in YellowstoneCounty and another outbreak later that year in McConeCounty

Dr. Jeanne Rankin, Acting State Veterinarian with the Montana Department of Livestock said anthrax spores are known to exist in soils in certain regions of Montana, and that isolated cases of anthrax can be expected to occasionally occur in the state. Outbreaks have occurred in both North and South Dakota this season, indicating climatic conditions are favorable for such a naturally occurring outbreak. Dr. Rankin urges livestock owners to contact their herd veterinarian immediately to investigate incidents of sudden, unexplained deaths in their herd.

Grazing animals are typically infected when they consume contaminated grass. By the time the animal shows clinical symptoms of the disease such as staggering, trembling, convulsions, or bleeding from body openings, death usually follows, untreated animals may die within 24-48 hours after infection. Dr. Rankin said animals primarily affected are cattle, sheep, goats, captive and domestic deer and horses. 

Human infection with anthrax may occur, and is usually the result of an occupational exposure involving direct contact with infected animals or animal products such as wool, hides and meat. According to Dr. Todd Damrow, State Epidemiologist with the Montana Department of Public Health and Human Services, Montana has not had a case of human anthrax reported since 1961.

When an outbreak is confirmed in a location, it is reasonable to expect additional cases within the same area. For herd owners in the region, vaccine can be purchased through local veterinarian’s office with prior approval from the State Veterinarian’s Office. Anyone administering the vaccine should wear a long-sleeved shirt and use latex or work gloves to prevent skin contamination with the “live” vaccine. Vaccination is recommended for livestock residing in or near an outbreak area or animals that will be moved into the area.

For anyone seeing open or bloated carcasses, do not move those carcasses as this could release bacteria into the air or further contaminate the surrounding ground causing further disease spread.  Do not salvage hides, horns, antlers, or any other tissue from the carcasses. Do not use heavy oils or tires to burn carcasses of affected animals; approved fuels are gasoline, diesel or wood. If an animal was housed in a barn, burn the animal’s bedding, manure and surrounding soil. To disinfect panels, trailers, or equipment, be sure to use an ammonia-based disinfectant labeled as effective for anthrax. Pastures where anthrax has occurred cannot be disinfected with chemicals, only burning ensures the bacteria have been killed and even then it is not guaranteed the burning will effectively kill the bacteria as the temperatures in the soil may not reach the necessary temperature.

Residents within an area should be aware to keep dogs out of pastures and away from carcasses during an outbreak. Although dogs are reportedly resistant to anthrax, they can develop infection from the bacteria and may require treatment. People and pets should not swim in stock tanks or stagnant ponds in pastures where death losses have occurred. Streams are considered safer as the moving water will dilute organisms. Animal carcasses in streams or rivers should be reported to the Department of Livestock.

Source: Montana Department of Livestock