The prevention of zoonotic diseases (those capable of transmission from animal to human populations) is the primary focus of animal importation regimes. Every nation (as well as supranational bodies such as the European Union) has established protocols concerning the admission of foreign animals into domestic jurisdictions. In the United States, various governmental departments and agencies assume concurrent jurisdiction for the development, promulgation (publishing), and enforcement of animal importation standards. The primary American bodies that direct these initiatives are the Centers for Disease Control (CDC), specifically the National Center for Zoonotic, Vector-Borne, and Enteric Diseases, and the United States Department of Agriculture (USDA).
The organized transport of livestock and other domesticated animals has played an important role in human food production since prehistoric times. The empires of Mesopotamia, Greece, and Rome employed successively more sophisticated methods to move desired animals more efficiently between various geographic regions.
WORDS TO KNOW
EPIZOOTIC: The abnormally high occurrence of a specific disease in animals in a particular area, similar to a human epidemic.
PRIONS: Prions are proteins that are infectious. Indeed, the name prion is derived from “proteinaceous infectious particles.” The discovery of prions and confirmation of their infectious nature overturned a central dogma that infections were caused by intact organisms, particularly microorganisms such as bacteria, fungi, parasites, or viruses. Since prions lack genetic material, the prevailing attitude was that a protein could not cause disease.
QUARANTINE: Quarantine is the practice of separating people who have been exposed to an infectious agent but have not yet developed symptoms from the general population. This can be done voluntarily or involuntarily by the authority of states and the federal Centers for Disease Control and Prevention.
STRAIN: A subclass or a specific genetic variation of an organism.
ZOONOSES: Zoonoses are diseases of microbiological origin that can be transmitted from animals to people. The causes of the diseases can be bacteria, viruses, parasites, and fungi.
The first Industrial Revolution (c.1780–1830) precipitated a European population surge that generated a corresponding demand for increased food production. After 1820, Britain was the world leader in the importation of cattle, securing both dairy and beef breeds from various parts of Europe to bolster its domestic stock. This burgeoning industry was essentially unregulated; any sickness or disease noted in an imported cattle herd or among domestic livestock that had contact with imported animals was regarded as a local phenomenon; contaminated beef was usually disguised by vendors and sold in the normal course of business.
In this laissez-faire industrial environment, the first great cattle epidemics swept both Britain and Europe after 1839. Foot and mouth disease (aphthovirus), bovine pleuro-pneumonia, and sheep pox were the most common of the epizootic outbreaks that posed significant challenges to veterinary medicine. The prominent British practitioner John Gamgee (1828-1886) was the first expert to propose the comprehensive government regulation of animals entering Britain to prevent “contagionism,” his rudimentary appreciation of the viral properties of these newly identified animal plagues.
Rinderpest (Morbillivirus), a highly infectious and fatal bovine virus, became the impetus to European government regulation of imported cattle. In 1865, rinderpest caused the deaths of over 400,000 cattle in Britain alone and an estimated one million more livestock across continental Europe. Britain established the world's first state veterinary service that year. Rinderpest is transmitted between animals through direct physical contact and has remained a potent agricultural industry threat across modern Africa, where war and political unrest have often prevented effective regulation of cattle imports.
There are three distinct but interrelated elements of the public interest that are addressed through governmental animal import controls: public health and disease prevention, the security of national food supplies, and enhanced scientific research capabilities.
Many types of imported livestock are intended for both breeding and direct food production. Cattle are the most prominent example of a dual-purpose animal. As all cattle breeds are susceptible to a myriad of highly contagious diseases, both zoonotic and bovine-specific, national import regulation is designed to anticipate such risks through mandatory inspections and reporting provisions.
The most prominent threat to the international animal importation regulatory framework was the discovery of bovine spongiform encephalopathy (BSE) in Britain in 1986. Also known as “mad cow disease,” BSE is a progressive and fatal neurological condition that ultimately destroys the function of an animal's central nervous system. BSE is highly contagious, although the incubation period of the disease is in excess of five years. The precise cause of BSE remains unknown, although there is a scientifically validated relationship between the disease and the presence in a subject animal of infectious proteins known as prions. The disease is most likely transmitted through either direct animal-to-animal contact or through the ingestion of feed prepared from the bone marrow of infected animals. Creutzfeldt-Jakob Disease (CJD) is a condition similar to BSE that occurs in humans; a variant of CJD is capable of being transmitted to humans through the consumption of BSE-contaminated beef.
The danger of BSE to both livestock and humans is so sufficiently grave that when a single cow was determined to be afflicted with BSE in Washington State in 2003, the Canada-United States border was closed to all cattle imports between each nation for 15 months. As BSE has no known treatment or cure except to slaughter and incinerate the affected animal, national border authorities inevitably erron the side of caution when BSE is suspected.
Scientific research involving animal experiments engages additional animal importation issues. The scientific community places a premium upon the ability to use monkeys and other non-human primates for research purposes, given the physiological similarities between these animals and humans. Primates also represent a significant risk to the human population as disease carriers.
The Ebola and Marburg viruses are the most prominent component of the Filoviridae family. African and Southeast Asian primates are known carriers of the various forms of these viruses. The strain that causes Ebola Hemorrhagic Fever (EHF) is a remarkably virulent virus that is transmitted by direct contact with a contaminated person or through the exchange of bodily fluids. EHF will trigger an often fatal attack upon the contaminated person's internal organs. The four most prolific out-breaks of Ebola occurred in the African nations of Zaire, Sudan, Gabon, and Cote d'Ivoire between 1976 and 1997, killing hundreds of people; in each instance the EHF mortality rates exceeded 60%. A typical victim will die within 21 days of contracting this disease.
It was for these reasons that the identification of a new Ebola strain at a primate research facility in Reston, Virginia in 1989 attracted significant international attention and touched off a fresh consideration of American research animal importation controls. The Reston animals were monkeys imported from the Philippines. Twenty-one of the animals were determined to have contracted this Ebola strain (later referenced as Ebola-R). Four human handlers became ill from exposure to Ebola-R, but each subsequently recovered. As the epidemiology and pathology of all Ebola variants remains poorly understood, strict importation rules, including express CDC permission for non-human primates, remain in force in the United States. The primary risk concerning a recurrence of Ebola-R in the United States or elsewhere is that this strain may mutate at a future time into a variant that is deadly to the human population.
The transport of pets across national borders is the third significant aspect of animal import regulation. Dogs and cats form the vast majority of such animals. The number of pet dogs owned worldwide is difficult to estimate; the two largest domestic dog populations are located in the United States (60 million dogs) and Brazil (30 million dogs) respectively. The sheer number of household pets and the corresponding ability of a large number of animal-borne zoonotic diseases to move quickly through a given population to infect both pets and humans has led to rigorous pet importation controls being enacted in most countries.
Exotic or unconventional pets, including large members of the cat family and various reptiles, are governed by species-specific regulations throughout the world. As an example, a turtle with a shell measuring less than 4 in (10 cm) in length may not be imported in to the United States without the advance permission of the CDC, due to a heightened risk to humans that Salmonellosis, a bacterial disease caused by contact with the bacterium Salmonella, may be contracted through the handling of these creatures.
Dogs and cats are subject to similar entry and quarantine regulations in most Western nations. In the United States, a pet cat or dog entering the country must be both quarantined and be proven free of any contagious disease. The standard requirement is a certificate from a licensed veterinarian confirming that the animal is free of rabies or any other infectious disease. The USDA possesses the discretion to quarantine any pet entering the United States, but, as a general rule, once rabies certification is available the animal will not be quarantined. These regulations apply equally to animals imported as pets or for breeding purposes. The most common of the zoonotic diseases sought to be contained through import control are rabies (Lyssavirus, transmitted through the bite of an infected animal), ringworm (Tinea, a fungal skin disease), and roundworm (Trinchinella spiralis, a parasitic worm that attacks a mammal's gastrointestinal tract).
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Centers for Disease Control and Prevention. “Frequently Asked Questions about Animal Importation.” <http://www.cdc.gov/ncidod/dq/faq_animal_importation.htm> (accessed June 8, 2007).
"Animal Importation." Infectious Diseases: In Context. . Encyclopedia.com. (June 24, 2019). https://www.encyclopedia.com/media/educational-magazines/animal-importation
"Animal Importation." Infectious Diseases: In Context. . Retrieved June 24, 2019 from Encyclopedia.com: https://www.encyclopedia.com/media/educational-magazines/animal-importation
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