How is tuberculosis (Tb) primarily transmitted among animals?

Tuberculosis (Tb) is primarily transmitted among animals through direct contact, most effectively via nose to nose contact. This mode of transmission allows for the exchange of respiratory secretions, which can contain mycobacteria, the causative agents of tuberculosis. In many animal species, particularly among certain mammals such as cattle and domestic pets, this close physical contact enables the bacteria to spread from an infected animal to a healthy one.

While other modes of transmission are possible, such as environmental contamination or contact with infected humans, they are not the primary routes for the spread of the disease in animal populations. For instance, contaminated environments can pose a risk, yet they tend to be less significant compared to direct contact among animals. Similarly, while humans can transmit Tb to animals, especially in zoonotic cases, this is not the primary transmission method for tuberculosis in animal hosts themselves. Thus, nose to nose contact is the correct answer regarding how tuberculosis spreads among animals.