Animal vaccination is the immunization of a domestic, livestock or wild animal. The practice is connected to veterinary medicine. The first animal vaccine invented was for chicken cholera in 1879 by Louis Pasteur. The production of vaccines for animals and humans has always been linked, this relationship has been coined 'One Health', as at least 61% of all human pathogens originate from animals. Two main examples of this link are the rabies and smallpox vaccines. The production of such vaccines encounter issues in relation to the economic difficulties of individuals, the government and companies.