The wildlife service-wing of the United States Department of Agriculture (USDA) is conducting a trial on the effectiveness of vaccinating wild deer for TB using feed.

The trial began last month and will run until April in the state of Michigan, with the vaccine-containing feed placed in at least 12 sites across tillage fields chosen for the project.

Cubes of alfalfa and molasses containing an edible sphere with a liquid BCG vaccine inside have been placed in areas known to be visited by wild deer in the trial site.

Any cubes not consumed by deer within two days are to be removed.

The USDA will then harvest deer from the area and analyse samples to test the efficacy of this method of deploying the vaccines.

Additional tools

Michigan has been attempting to eradicate TB for the past 30 years, and although disease rates have dropped in both deer and cattle, the project team stated that “there's a need for the development of additional tools that can complement ongoing efforts in the state”.

The project has stated that vaccinated deer are not completely immune or fully protected from TB infection, but earlier trials suggest that BCG vaccinated deer are less likely to actively transmit the disease and can reduce its spread.

While it is not known for exactly how long these effects last after vaccination, but it is thought to be for around one year, according to the USDA.

There is currently no TB vaccine licensed for use on cattle in the US, as it cannot be differentiated if a vaccinated animal is infectious or has just been vaccinated – a fact which could mask the disease in vaccinated herds and hinder eradication efforts.