Epizootic
In epizoology, an epizootic (from Greek: epi- upon + zoon animal) is a disease event in a nonhuman animal population, analogous to an epidemic in humans. An epizootic may be: restricted to a specific locale (an "outbreak"), general (an "epizootic") or widespread ("panzootic"). High population density is a major contributing factor to epizootics. Aquaculture is an industry sometimes plagued by disease because of the large number of fish 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 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.
Equine influenza
Equine influenza (horse flu) is the disease caused by strains of influenza A that are enzootic in horse species. Equine influenza occurs globally, and is caused by two main strains of virus: equine-1 (H7N7) and equine-2 (H3N8). The disease has a nearly 100% infection rate in an unvaccinated horse population with no prior exposure to the virus.
While equine influenza is historically not known to affect humans, impacts of past outbreaks have been devastating due to the economic reliance on horses for communication (postal service), military (cavalry), and general transportation. In modern times, though, the ramifications of equine influenza are most clear in the horse-racing industry.
Characteristics
Equine influenza is characterized by a very high rate of transmission among horses, and has a relatively short incubation time of one to five days. Horses with horse flu can run a fever, have a dry, hacking cough, have a runny nose, and become depressed and reluctant to eat or drink for several days, but they usually recover in two to three weeks.
