Listeriosis is a sporadic bacterial infection that affects a wide range of animals, including people and birds. It is seen worldwide, more frequently in temperate and colder climates. There is a high incidence of intestinal carriers. Encephalitis or meningoencephalitis in adult ruminants is the most frequently recognized form. They are 7 types of listeria species but L.monocytogenes is the only pathogenic for both humans and animals. The aim of this book is to review and compile the available literature of listeriosis in animals, diagnosis, etiology and its public health.