epizoology Epizootiology, epizoology, or veterinary epidemiology is the study of disease patterns within animal populations. See also * Epizootic * Epidemiology Epidemiology is the study and analysis of the distribution (who, when, and where), patterns ...

, an epizootic (or epizoötic, from Greek: ''epi-'' "upon" + ''zoon'' "animal") is a

disease A disease is a particular abnormal condition that adversely affects the structure or function (biology), function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical condi ...

event in a nonhuman

animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...

population analogous to an epidemic in humans. An epizootic disease (or ) may occur in a specific locale (an " outbreak"), more generally (an "epizootic"), or become widespread (" panzootic"). High population density is a major contributing factor to epizootics. The aquaculture industry is sometimes plagued by disease because of the large number of

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

confined to a small area. Defining and declaring an epizootic can be subjective; health authorities evaluate the number of new cases in a given animal population during a given period, and estimate a rate of spread that substantially exceeds what they might expect based on recent experience (''i.e.'' a sharp elevation in the incidence rate). Because the judgement is based on what is "expected" or thought normal, a few cases of a very rare disease (like a transmissible spongiform encephalopathy outbreak in a cervid population) might be classified as an "epizootic", while many cases of a common disease (like lymphocystis in esocids) would not. Common diseases that occur at a constant but relatively high rate in the population class as " enzootic" (compare the epidemiological meaning of "endemic" for human diseases). An example of an enzootic disease would be the influenza virus in some bird populations or, at a lower incidence, the Type IVb strain of viral hemorrhagic septicemia in certain Atlantic fish populations. An example of an epizootic was the 1990 outbreak of Newcastle disease virus in double-crested cormorant colonies on the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

that resulted in the death of some 10,000 birds.Viral Hemorrhagic Septicemia (VHS) - HSL
''www.usgs.gov'', accessed 8 May 2020

References

{{Authority control Animal diseases History of veterinary medicine