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 ...

, an epizootic (from Greek: ''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 Ancient Greek, 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 ...

in humans. An epizootic may be restricted to a specific locale (an " outbreak"), general (an "epizootic"), or widespread ("

panzootic A panzootic (from Greek παν all + ζόιον animal) is an epizootic (an outbreak of an infectious disease of animals) that spreads across a large region (for example a continent), or even worldwide. The equivalent in human populations is calle ...

"). High

population density Population density (in agriculture: 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 term.Matt RosenberPopul ...

is a major contributing factor to epizootics.

Aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

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% of li ...

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 Lymphocystis is a common viral disease of freshwater and saltwater fish. The virus that causes this disease belongs to the genus ''Lymphocystivirus'' of the family Iridoviridae. Aquarists often come across this virus when their fish are stressed ...

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 elsew ...

" for human diseases). An example of an enzootic disease would be the

influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...

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 v ...

in certain Atlantic fish populations. An example of an epizootic would be the 1990 outbreak of Newcastle disease virus in

double-crested cormorant The double-crested cormorant (''Nannopterum auritum'') is a member of the cormorant family of water birds. It is found near rivers and lakes, and in coastal areas, and is widely distributed across North America, from the Aleutian Islands in Alas ...

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 lakes ...

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