in epizootiology, a place frequented by the source or sources of an infectious or infestant agent, that is, a diseased animal, a microbe carrier, where under certain conditions it is possible to transmit the agent to a susceptible animal.
An epizootic focus may be a structure, such as a cattle yard, sheep pen, pig sty, or poultry house, or open land, such as pastures or areas around buildings used for livestock breeding. A building or area is declared an epizootic focus when some form of an infection has been discovered among the animals. Epizootic foci of wild animals include forests and meadows.
The size of an epizootic focus depends on the type of disease, in particular, on the means of transmission of the agent, and on the conditions under which the disease runs its course. The epizootic focus in certain diseases of stabled animals, such as strangles of horses, is usually limited to the buildings in which the animals are grouped. In highly contagious diseases, such as foot-and-mouth disease, and in diseases transmitted by parasites, such as African horse sickness, the focus may be quite extensive. The epizootic focus should be distinguished from the infected location, in which there are no sources of the infectious agent, but in which objects of the environment have been inoculated with pathogenic microflora.
An epizootic focus is considered eliminated under the following conditions: the source of the infectious agent has been rendered harmless (after the recovery or slaughter of sick animals), microbe carriers are absent, appropriate sanitation measures have been taken, and the time equivalent to the disease’s maximum incubation period has passed.