Epidemiological Investigation of Listeriosis Outbreak among Beouins from Southern District

Introduction: Listeriosis is an infectious disease caused by Listeria monocytogenes. Transmission is mediated mostly by contaminated food, and the level of infectivity is determined by the immunological status of the host and can be detrimental for pregnant women, causing miscarriage and birth defects. During the years 2017-2018, a major rise in listeriosis was noted in the Bedouin population of the South.

Aims: To describe the epidemiological investigation of the outbreak and the means taken towards elimination.

Methods: An extensive epidemiological investigation to identify the source of the contaminated food combined with health education activities.

Results: Out of total 43 cases of listeriosis reported to the Southern District Health Office, 33 belong to the same cluster, using Pulsed-filed Electrophoresis (PFGE) and complete genomic sequencing. All were reported from the Bedouin community. Majority of the cases were in pregnant women (24) and people with existing health conditions (6). Hundreds of food samples were collected from households of patients who agreed to take part in the investigation, from vendor and other sources. All were tested in the laboratory to assess their relevance for the outbreak cluster. Results pointed to several directions, but eventually positive cultures from food samples produced in a meat factory in East Jerusalem were found linked to the outbreak and pointed to a probable cause.

Conclusions: Listeriosis cluster investigations should include a team of epidemiological researchers, food inspectors, and professional food-lab technicians, to allow an efficient identification of the outbreak source and its elimination. This should be combined with education for proper food purchasing habits, storing, cooking and consuming.

Keywords: Epidemiological investigation, listeriosis outbreak, food safety, Listeria monocytogenes.

Affiliations: All Authors are employed by the Southern District Health Office, Israel Ministry of Health. (e-mail: limor.azulay@bsh.HEALTH.GOV.IL, maya.rabani@bsh.health.gov.il)