Which of the following is a risk factor for introducing M. bovis into cattle herds?

The option identifying the movement of humans and animals from areas where tuberculosis (TB) is prevalent as a risk factor for introducing M. bovis into cattle herds is correct because this movement can facilitate the transmission of the disease. Mycobacterium bovis, the bacterium that causes TB in cattle, can be carried by infected wildlife and even humans, particularly in regions where TB is common. When animals or people migrate from such areas, they can inadvertently introduce the pathogen into previously unaffected cattle populations. This underscores the importance of monitoring and controlling animal and livestock movement to prevent the spread of diseases like bovine TB.

On the other hand, widespread pasteurization of dairy products serves as a protective measure rather than a risk factor. Similarly, the vaccination of cattle against TB aims to reduce disease prevalence and transmission, making it less likely for M. bovis to enter herds. Increased organic farming practices, while potentially leading to different management strategies, do not inherently increase the risk of M. bovis introduction, especially since organic farms might adopt stringent biosecurity measures. Hence, the movement of infected individuals and animals from endemic areas remains a significant risk factor for the introduction of M. bovis into cattle herds.