Epizootic

An epizootic is a disease event in which there is a rapid increase in the number of disease cases in an animal population within a particular geographic area, exceeding the expected baseline. The term is used in veterinary epidemiology to describe outbreaks in animals and is the counterpart to an epidemic in humans. Epizootics can involve domestic, livestock, or wild populations and may be caused by infectious agents such as viruses, bacteria, parasites, or fungi, or by noninfectious factors like toxins or environmental stressors.

Transmission can occur through direct contact, aerosols, vectors, contaminated feed or water, or movement of animals. Factors that promote epizootics include high population density, weakened immunity, climate and seasonal changes, and international trade or movement of animals. The course of an epizootic is influenced by host susceptibility, pathogen characteristics, and environmental conditions.

Management and control aim to rapidly detect and contain outbreaks to limit animal suffering, economic losses, and the risk of spillover to humans. Measures commonly employed include active surveillance and reporting, quarantine and movement controls, vaccination where available, improvements in biosecurity, selective culling or segregation in livestock settings, and vector or environmental management.

Examples of notable epizootics include avian influenza outbreaks among poultry and wild birds, bluetongue disease in ruminants, African swine fever outbreaks in pigs, and outbreaks of rabies in wildlife. Some epizootics have zoonotic potential, meaning they can pose a risk to human health through direct contact or via vectors.