Veterinary advice should be sought from your local veterinarian before applying any treatment or vaccine. Not sure who to use? Look up veterinarians who specialize in poultry using our directory listing. Find me a Vet


Other Names: Circling Disease, Listeria Monocytogenes Infection

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.


L. monocytogenes 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.

Clinical Signs

Torticollis (wry neck)
Head tilt
Loss of appetite
Weight loss
Not laying eggs
Diarrhea with yellow-white feces
Inability to stand


  • History
  • Clinical signs
  • CFT
  • Necropsy

Reported Cases

  • Case 1: Listerial encephalitis in a Partridge An outbreak of neurological disease was investigated in red-legged partridges between 8 and 28 days of age. Clinical signs included torticollis, head tilt and incoordination and over an initial eight day period approximately 30–40 fatalities occurred per day. No significant gross post mortem findings were detected. Histopathological examination of the brain and bacterial cultures followed by partial sequencing confirmed a diagnosis of encephalitis due to Listeria monocytogenes. Further isolates were obtained from follow-up carcasses, environmental samples and pooled tissue samples of newly imported day-old chicks prior to placement on farm. Ref

  • Case 2: Listeriosis in a Chickens Five chickens from a backyard flock of 20 eight-month-old birds started displaying clinical signs of depression, anorexia, reduced comb size, pasty butt, and panting. Most of the hens stopped laying eggs. Seven birds from the same flock had died in the previous 5 months. The flock owner occasionally fed the birds fresh garden produce that was grown on the premises. A few of the dead birds were sent to the local veterinary diagnostic lab for a necropsy. The pathologic changes in the internal organs of infected birds showed severe myocarditis, pericarditis, pneumonia, hepatitis, and splenitis. No lesions were noted in the brain. Gram-positive organisms were seen in histologic sections of the heart and spleen. Listeria monocytogenes was detected by real time PCR from formalin fixed heart and spleen, and was isolated from fresh lung, spleen, and liver. The exact source of infection for this flock is unknown. Possible sources of the Listeria infection include feces, soil, decaying plant material, feed, and water. Neither the environment where the chickens were housed nor the commercial ration or drinking water were collected or tested. The first clinical signs in the flock appeared when investigation from a multistate outbreak of listeriosis linked to whole cantaloupes was ongoing. The remaining sick birds were treated intramuscularly with 25 mg/kg of enrofloxacin for 5 days. All the birds recovered. Ref

  • Case 3: Listeriosis in a Cockatiel Listeriosis was diagnosed in a 4-yr-old female cockatiel that died after exhibiting clinical signs that included a fluffed-up appearance, weakness, and loss of weight of several days duration. Grossly, the bird was moderately emaciated, and the liver and spleen were enlarged. Microscopically, there was mild-to-moderate inflammation associated with rod-shaped, gram-positive bacteria in the liver, spleen, kidneys, adrenal glands, bone marrow, and esophagus. Listeria monocytogenes was isolated from the liver, trachea, and intestine. The isolate was identified as type 1 by agglutination with specific antisera, and it further identified as belonging to serovar group 1/2a, 3a by multiplex polymerase chain reaction assay. Listeria monocytogenes also was detected in affected tissues by immunohistochemistry. Ref


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Enrofloxacin25 mg/kg BW administered IM for 5 daysR Crespo et al
Virginiamycin22 mg/kg administered QD in feedK Marx



  • Practice good sanitary management practices
  • Develop biosecurity guidelines
  • Thoroughly wash vegetables and fruits before feeding to birds

Scientific References

Good Overviews

Age Range

Young birds are more susceptible to infection, but occurs in birds of any age.

Risk Factors

  • Regularly feeding birds raw vegetables and fruits that have not been thoroughly washed first
  • Feeding birds soft cheeses