Inhalation of ruminal gases is the most common route of entry for the mycobacterium organism, and spread of the disease is usually via cow-to-cow contact via aerosol. Cattle can also become infected by ingestion of the causative agent; this is the usual route of entry when the badger is involved, by infecting grazing land or water troughs. Calves with infected dams can become affected via the milk, and intrauterine infection at coitus has been reported. | Inhalation of ruminal gases is the most common route of entry for the mycobacterium organism, and spread of the disease is usually via cow-to-cow contact via aerosol. Cattle can also become infected by ingestion of the causative agent; this is the usual route of entry when the badger is involved, by infecting grazing land or water troughs. Calves with infected dams can become affected via the milk, and intrauterine infection at coitus has been reported. |