Rattles is a severe and potentially fatal disease of Thoroughbred foals, caused by the bacterium Rhodococcus equi. As the bacterium is present in virtually all soils it is very difficult to prevent foals from being exposed to it. Up to 20% of foals exposed to the bacterium will develop severe pneumonia known as rattles. These severe cases will require veterinary intervention and likely be treated using a combination of antibiotics. Approximately 28% of foals affected by rattles will die from the disease. The project team has developed a vaccine to reduce the risk of foals developing rattles. The vaccine is a disabled virus that produces a protein from the bacterium to train the immune systems of foals to generate protective immune responses. The vaccine has been tested in a mouse disease model which demonstrated strong and protective immune responses. This project aims to test the vaccine in foals to evaluate its safety and capacity to induce specific immune responses to the bacterial protein. After the successful completion of this project, the vaccine performance data will be used to recruit a veterinary health company to undertake the further development and commercialisation processes to deliver it to the Australian Thoroughbred industry.