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In epizoology, an 'epizootic' (from Greek ''epi-'' upon + ''zoion'' animal) is a disease that appears as new cases in a given animal population, during a given period, at a rate that substantially exceeds what is "expected" based on recent experience (''i.e.'' a sharp elevation in the incidence rate). (An epidemic is the same term applied to human populations.) High population density is a major contributing factor to epizootics, with aquaculture being an example of an industry sometimes plagued by disease because of the large number of fish confined to a small area.
Defining an epizootic can be subjective, depending in part on what is "expected". An epizootic may be: a) restricted to a specific locale (an outbreak), b) general (an "epizootic") or c) widespread (panzootic). Because it is based on what is "expected" or thought normal, a few cases of a very rare disease (like a TSE 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 are said to be "enzootic." An example of an enzootic disease would be the influenza virus in some bird populations [1] or, at a lower incidence, the Type IVb strain of VHS in certain Atlantic fish populations. [2]
An example of an epizootic would be the 1990 outbreak of Newcastle disease virus in double-crested cormorant colonies on the Great Lakes that resulted in the death of some 10000 birds. [3]

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See also

See also

★ Epidemic

★ Enzootic

★ Epizoology

★ Panzootic

★ Synzootic

★ Mathematical modelling in epidemiology