In the early stages of the disease, lesions are difficult to find. In later stages, nodules or lumps may be found in the lungs and associated lymph nodes as well as in the lymph nodes of the head and intestinal tract. Bovine Tb can be transmitted from cattle to other farm animals, bison, and all of the deer species under certain conditions. Cattle are the usual host for this bacteria. The most common means is by airborne transmission.
Infected animals exhale bacteria through breathing, coughing and sneezing.
Animals are more likely to infect each other when they share a common watering and feeding place. Bovine tuberculosis is not a naturally occurring disease in wild animals. It is thought that it was introduced into wildlife populations through contact with domestic animals. Although it is known that wild herds can become infected with Tb, results from specific hunter surveys in Manitoba and Alberta, and the capture and testing of wild animals for domestic and zoological purposes indicate that the disease is still not common in wild animals in Canada. Responsibility for controlling disease rests with the agency that has legal jurisdiction over wildlife species.