In
epizoology, an epizootic (from
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
: ''epi-'' upon + ''zoon'' animal) is a
disease
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
event in a nonhuman animal population analogous to an
epidemic
An epidemic (from Greek ἐπί ''epi'' "upon or above" and δῆμος ''demos'' "people") is the rapid spread of disease to a large number of patients among a given population within an area in a short period of time.
Epidemics of infectious d ...
in humans. An epizootic may be restricted to a specific locale (an "
outbreak
In epidemiology, an outbreak is a sudden increase in occurrences of a disease when cases are in excess of normal expectancy for the location or season. It may affect a small and localized group or impact upon thousands of people across an entire ...
"), general (an "epizootic"), or widespread ("
panzootic"). High
population density
Population density (in agriculture: Stock (disambiguation), standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans, but sometimes to other living organisms too. It is a key geographical ...
is a major contributing factor to epizootics.
Aquaculture is an
industry sometimes plagued by disease because of the large number of
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...
confined to a small area.
Defining an epizootic can be subjective; it is based upon the number of new cases in a given animal population, during a given period, and must be judged to be a rate that substantially exceeds what is expected based on recent experience (''i.e.'' a sharp elevation in the
incidence rate). Because it 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 are said to be "
enzootic" (''cf.'' the epidemiological meaning of "
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...
" 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
Viral hemorrhagic septicemia (VHS) is a deadly infectious fish disease caused by Viral hemorrhagic septicemia virus. It afflicts over 50 species of freshwater and marine fish in several parts of the Northern Hemisphere. Different strains of the ...
in certain Atlantic fish populations.
An example of an epizootic would be 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 in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five la ...
that resulted in the death of some 10,000 birds.
Viral Hemorrhagic Septicemia (VHS) - HSL
''www.usgs.gov'', accessed 8 May 2020
See also
References
{{Authority control
Animal diseases
History of veterinary medicine