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Outbreak of Listeria monocytogenes in an Urban Poultry Flock

28 October 2013

A first report describing an outbreak of Listeria monocytogenes causing depression, anorexia, panting and mortality in a backyard poultry flock in Washington State, US.

Listeria monocytogenes infection is most commonly recognised in ruminants, including cattle, sheep, and goats; but it is rarely diagnosed in poultry.

In BMC Veterinary Research, Rocio Crespo of Washington State University and co-authors at research institutes in the same state report an outbreak of L. monocytogenes in a backyard poultry flock.

The case highlights the importance of collaboration between veterinarians and public health departments and the possible implications of zoonotic diseases.

Depression, lack of appetite, laboured breathing and increased mortality were noted for five months in several affected birds within the flock, which were first examined when about eight months of age.

The pathological changes in the internal organs of infected birds included severe myocarditis, pericarditis, pneumonia, hepatitis and splenitis. No lesions were noted in the brain.

Gram-positive organisms were seen in histological sections of the heart and spleen.

L. monocytogenes was detected by real-time PCR from formalin fixed heart and spleen, and was isolated from fresh lung, spleen, and liver. This isolate was identified as L. monocytogenes serotype 4b by 16S rDNA sequencing and by PCR-based serotyping assay. This is one of the most pathogenic serovars that is known to cause majority of human infections.

The exact source of infection for this flock is unknown, report Crespo and co-authors. Possible sources of the Listeria infection include faeces, soil, decaying plant material, feed and water. However, neither the environment where the chickens were housed nor the commercial ration or drinking water were collected or tested. Furthermore, various species of mammals and birds have been shown in other work to be infected with Listeria and may serve as asymptomatic carriers. The first clinical signs in the flock appeared when investigation from a multi-state outbreak of listeriosis linked to whole cantaloupes was ongoing,

Crespo and co-authors say that this is the first report describing outbreak of L. monocytogenes in backyard poultry flock in Washington State and use of molecular methods to confirm L. monocytogenes infection from formalin fixed tissues.


Crespo R., M.M. Garner, S.G. Hopkins and D.H. Shah. 2013. Outbreak of Listeria monocytogenes in an urban poultry flock. BMC Veterinary Research. 9:204. doi:10.1186/1746-6148-9-204

Further Reading

You can view the full report by clicking here.

October 2013

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