LAKEWOOD, Colo. – Officials confirmed that an outbreak of anthrax has expanded in northeast Colorado after two more cows died from the disease, according to the Associated Press.

The Colorado Department of Agriculture said Aug. 15 the two cows were on two separate but adjacent ranches. The previous week, 60 cows died at a Logan County ranch. One animal tested positive for anthrax. Animal health officials said all the cows likely died of the disease, according to AP.

“This is not an uncommon occurrence with anthrax because adjacent properties may also contain the anthrax spores in the soil; we certainly hoped there wouldn’t be other herds affected but this is the nature of the disease,” said State Veterinarian, Dr. Keith Roehr in a statement. “We will expand our efforts onto the adjacent premises to protect the health of these cattle. At this time, all of the neighboring herds have been vaccinated for anthrax and affected herds are being treated.”

According to the Colorado Department of Agriculture, all of the initially infected carcasses were incinerated. Incineration kills anthrax spores and is the best means of disposal of the carcasses, according to the department.

Anthrax is caused by Bacillus anthracis, a bacterium that forms spores. Cattle, sheep, horses and goats are most susceptible to the disease. Humans or animals can become infected by coming in contact with infected animals, soil or water. Anthrax can be treated with antibiotics, especially if its caught early. There is a vaccine for humans and livestock.