Contagious animal diseases may be spread internationally by the importation of carcass meats or animal products from areas where a disease is enzootic, or as a result of the transit of live animals. A transit country faced with the threat of contagious disease may slaughter and destroy the contaminated goods and refuse future shipments from the country of origin. Thus the health interests of transit countries may impede the international trade in animals, meat and other products of animal origin.
The problem occurs particularly with diseases where the causative agent is resistant to freezing, such as in the case of the foot-and-mouth disease virus, and that of fowl pest. The foot-and-mouth disease virus has been known to remain active in the bone marrow of pork and beef for 76 days, even at freezing temperatures. Such carcasses can infect human beings who may act as carriers of the disease to animals. The fowl pest virus can exist for 2 years in frozen birds.