View source for Epizootic

{{short description|Animal disease event, analogous to an epidemic}}
{{Distinguish|Epizoic}}
[[File:Rinderpest 1896-CN.jpg|thumb| [[Rinderpest]] outbreak in [[South Africa]], 1896]]

In [[epizoology]], an '''epizootic''' (or '''epizoötic''', from [[Greek language|Greek]]: ''epi-'' "upon" + ''zoon'' "animal") is a [[disease]] event in a nonhuman [[animal]] population analogous to an [[epidemic]] in humans.  An epizootic disease (or '''{{linktext|epizooty}}''') 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 (economics) |industry]] is sometimes plagued by disease because of the large number of [[fish]] 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 (epidemiology) |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 [[Esox|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 (epidemiology)| "endemic"]] for human diseases). An example of an enzootic disease would be the [[influenza]] virus in some bird populations<ref>{{cite web|url= https://wwwnc.cdc.gov/eid/articles/issue/12/1/table-of-contents |title=Volume 12, Number 1—January 2006 - Emerging Infectious Disease journal - CDC |work= Cdc.gov |access-date=2012-06-06}}</ref> or, at a lower incidence, the Type IVb strain of [[viral hemorrhagic septicemia]] in certain Atlantic fish populations.<ref>{{Cite web |url= http://www.michigan.gov/documents/dnr/Viral-Hemorrhagic-Septicemia-Fact-Sheet-11-9-2006_178081_7.pdf |title= Archived copy |access-date=2007-05-24 |archive-date=2007-03-09 |archive-url= https://web.archive.org/web/20070309010426/https://www.michigan.gov/documents/dnr/Viral-Hemorrhagic-Septicemia-Fact-Sheet-11-9-2006_178081_7.pdf |url-status=dead }}</ref><ref>[https://www.inspection.gc.ca/animal-health/aquatic-animals/diseases/reportable-diseases/vhs/fact-sheet/eng/1327210643614/1327210771329 Viral Hemorrhagic Septicemia (VHS) - Fact Sheet] ''www.inspection.gc.ca'', accessed 8 May 2020</ref>

An example of an epizootic was the 1990 outbreak of [[Newcastle disease]] virus in [[double-crested cormorant]] colonies on the [[Great Lakes]] that resulted in the death of some 10,000 birds.<ref>{{Cite web |url= http://www.nwhc.usgs.gov/publications/field_manual/chapter_21.pdf |title=Archived copy |access-date=2007-05-24 |archive-date=2007-07-11 |archive-url= https://web.archive.org/web/20070711064624/http://www.nwhc.usgs.gov/publications/field_manual/chapter_21.pdf |url-status=dead }}
</ref><ref>[https://www.usgs.gov/centers/wfrc/science/viral-hemorrhagic-septicemia-vhs-hsl?qt-science_center_objects=0#qt-science_center_objects Viral Hemorrhagic Septicemia (VHS) - HSL] ''www.usgs.gov'', accessed 8 May 2020</ref>

==See also==
{{Portal|Medicine}}
{{columns-list|colwidth=30em|
*[[Epidemic]]
*[[Enzootic]]
*[[Epizoology]]
*[[Panzootic]]
*[[Equine influenza]] for the Great Epizootic of 1872 in the US and Canada
*[[1890s African rinderpest epizootic]]
*[[Mathematical modelling in epidemiology]]
*[[Sylvatic plague]]
*[[Wildlife disease]]}}

==References==
{{wikt | epizootic}}
{{Reflist}}

{{Authority control}}
[[Category:Animal diseases]]
[[Category:History of veterinary medicine]]