There is some evidence of immunity passed on in genes, however all animals exposed to the bacterium are considered at high risk of infection. In animals, lateral as well as vertical transmission is common, as the disease is passed through nose to nose contact and shared feed and watering troughs. Animals are most commonly infected by introduction to the respiratory or digestive tract, but also can be directly infected via an open wound. Exposure to infection, overcrowding, and an unsanitary environment are major factors contributing to transmission. The incidence of transmission to wild animals is considered rare, but it rises quickly as their association with humans and domestic animals increases.
High incidence is seen in captive wildlife, similar to the distribution observed in cattle.
Some animals show few or no outward signs of infection, resulting in transmission to the herd before detection. In extreme cases pulmonary infection and subsequent lesion development causes a low, chronic, moist cough which may progress to bronchitis, broncho-pneumonia, and eventual respiratory failure. In chronic cases loss of appetite, painless swelling of the lymph nodes and emancipation are observed. Most ungulates develop a chronic long-term wasting disease, as seen in infected domestic cattle. In male deer abnormal antler development is observed, although such alterations of antler growth are a symptom of various other diseases and starvation.