WGS data used for surveillance of Campylobacter infections resulted in the detection of a large continuous outbreak, Denmark, 2019

Human campylobacteriosis is the most commonly reported zoonotic disease in Europe, with 246,571 reported cases in the European Union (EU) in 2018. Denmark had 5,389 cases in 2019. The surveillance found that 33% of chicken meat samples were positive for Campylobacter at slaughter. Campylobacter infections are predominantly food-borne, with poultry as the primary source. WGS-based surveillance of clinical cases and chicken samples improved our understanding of the occurrence and dynamics of Campylobacter strains in chicken meat and the correlation to clusters of human cases. The surveillance showed that numerous Campylobacter infections were not sporadic but rather part of a more significant outbreak. A significant impact of the 2019 surveillance showed that the apparent association of a substantial proportion of the human Campylobacter cases to the Danish chicken production had increased the poultry industry’s awareness. The large outbreak of Campylobacter has led to extensive initiatives and investments targeting Campylobacter throughout the production chain. The new knowledge and awareness could lead to a decrease in the Danish chicken-associated human cases of campylobacteriosis in the coming years. @ https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2021.26.22.2001396?emailalert=true#html_fulltext

Eurosurveillance | Whole genome sequencing data used for surveillance of Campylobacter infections: detection of a large continuous outbreak, Denmark, 2019

Campylobacter is one of the most frequent causes of bacterial gastroenteritis. Campylobacter outbreaks are rarely reported, which could be a reflection of a surveillance without routine molecular typing. We have previously shown that numerous small outbreak-like clusters can be detected when whole genome sequencing (WGS) data of clinical Campylobacter isolates was applied.
Typing-based surveillance of Campylobacter infections was initiated in 2019 to enable detection of large clusters of clinical isolates and to match them to concurrent retail chicken isolates in order to react on ongoing outbreaks.
We performed WGS continuously on isolates from cases (n = 701) and chicken meat (n = 164) throughout 2019. Core genome multilocus sequence typing was used to detect clusters of clinical isolates and match them to isolates from chicken meat.
Seventy-two clusters were detected, 58 small clusters (2–4 cases) and 14 large clusters (5–91 cases). One third of the clinical isolates matched isolates from chicken meat. One large cluster persisted throughout the whole year and represented 12% of all studied Campylobacter cases. This cluster type was detected in several chicken samples and was traced back to one slaughterhouse, where interventions were implemented to control the outbreak.
Our WGS-based surveillance has contributed to an improved understanding of the dynamics of the occurrence of Campylobacter strains in chicken meat and the correlation to clusters of human cases.

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