Listeriosis is an infectious and fatal disease of animals, birds, fish, crustaceans, and humans that is caused by infection with Listeria monocytogenes
. L. monocytogenes
is an intracellular pathogen which has a unique ability to spread from cell to cell, allowing it to cross blood-brain intestinal and placental barriers. The organism is widespread in nature, and has been isolated from animals, humans, food sources (milk, meat and meat products, seafood, and fresh vegetables and fruits), and the environment (soil, decaying plants, water) and known for causing sporadic outbreaks worldwide.
The clinical signs of listeriosis vary, depending on the amount ingested, pathogenic properties of the specific strain, and the immune condition of the bird. The most common Listeria
infections are caused by three serotypes: 1/2a, 1/2b, and 4b. In chickens, listeriosis has been associated with two major forms----septicemic and encephalitic. There is a third form that occurs in humans and other animals, the abortion form, but it has not been characterized yet in chickens.
- Encephalitic form: Sometimes referred to as "circling disease", this form is characterized by neurologic signs such as incoordination, torticollis, hyperthermia, loss of appetite, depression, and walking in circles.
- Septicemic form: This form is characterized by diarrhea, depression, and emaciation.
is transmitted to chickens predominately through ingestion, inhalation, or direct contact with the Listeria
bacterium. L. monocytogenes
has also been linked to diverse types of fresh produce such as sprouts, celery, cantaloupe, stone fruit, and apples. Contamination with L. monocytogenes
is the third leading cause of food-borne illness in the United States.
Listeriosis occurs more commonly in birds living in the northern and southern latitudes and temperate climates. In northern hemispheres, listeriosis has been found to occur more frequently between December to May.