Ans: Epizootic comes from two Greek words epi (meaning upon) and zoon (meaning animal) and it is a disease event seen in the animal population. Epizootic is analogous to epidemics in humans. Epizootics could be restricted to a specific area (called an outbreak), or widespread (called a panzootic). An example of epizootic is RVF (Rift valley fever) which primarily affects livestock and can affect a large number of domestic animals (the presence of RVF could also lead to an epidemic in humans who get exposed to diseased animals). The major factor behind epizootics is high population density for example the aquaculture industry is plagued with epizootics since in this industry a large population of fishes is kept in a confined area.