The livestock-wildlife interface in infectious disease transmission — the bovine TB example in Michigan (Proceedings)

Nov 01, 2010

The issue of disease transmission between species is nothing new. Veterinarians have always been aware of the potential risk of wildlife being a source of disease transmission to livestock. A classic example is transmission of Leptospirosis species from wildlife to cattle via urine contamination of the environment. Transmission of diseases between domestic livestock species has led to management practices to reduce this risk. As a simple example, cattle and sheep are less likely to be housed together because of the risk of malignant catarrhal fever transmission from carrier sheep to highly susceptible cattle.

Transmission of infectious agents between cattle and wildlife are dependent on many factors. These include specific behaviors, management practices, physiologic events, environmental circumstances behavior and density of host species, climatic conditions, and overlap of host range with other susceptible species. Attributes of the specific infectious agent and the disease characteristics are also important. These factors include an agent's ability to infect a new host, the routes of entry and exit from the normal and new host, the course of a disease (acute -vs- chronic), time interval for shedding, and overall morbidity and mortality. Depending on these factors, a new host may be a "dead-end" host or it may become a maintenance host, able to maintain infection without continual introduction from other species.

Table 1: Summary of Bovine TB positive farms in Michigan, 1997-2010
As veterinarians, we must be aware of the risks for disease transmission from wildlife species to domestic livestock and counsel clients on these risks. As we understand the potential disease risks and how transmission occurs, risk mitigation strategies can be employed. What follows is a description of Bovine tuberculosis in Michigan as an example of disease spread from wildlife to cattle and how that spread may be managed.

Bovine Tuberculosis in Michigan


