Human Campylobacteriosis Cases Traceable to Chicken Meat—Evidence for Disseminated Outbreaks in Finland

Abstract

Campylobacter jejuni (C. jejuni) is the most common cause of human bacterial gastroenteritis in the world. Food-borne campylobacteriosis is thought to be commonly caused by the handling and consumption of undercooked chicken meat, but the epidemiology of this disease is complex and remains poorly characterized, especially in the Nordic countries. Here, we used state-of-the-art methods in genetic epidemiology combined with patient background and temporal association data to trace domestically acquired human C. jejuni infections (n = 50) to chicken meat, in a midsize Nordic town in Finland during a seasonal peak. Although 59.2% of the human isolates shared a sequence type (ST) with a chicken batch slaughtered prior to the onset of disease, further analysis at the whole-genome level (core genome and whole-genome multilocus sequence typing, cgMLST and wgMLST, respectively) traced a mere nine cases (18.4%) to fresh chicken meat. Human isolates also shared genotypes with isolates collected from chicken batches slaughtered after the onset of the human disease, highlighting the role of alternative transmission pathways from chickens to humans besides the food chain, or a shared third source. The high resolution offered by wgMLST, combined with simple metadata, offers a more accurate way to trace sporadic cases to possible sources and reveal disseminated outbreak clustering in time, confirming the importance of complementing epidemiological investigations with molecular epidemiological data.

Observations supporting hypothetical commensalism and competition between two Campylobacter jejuni strains colonizing the broiler chicken gut

“…The majority of campylobacteriosis cases in humans are sporadic, except for virulent Campylobacter species that would appear to be associated with diffuse outbreaks (Llarena et al, 2016). Some outbreaks are reported in the literature after the consumption of undercooked chicken meat (Yu et al, 2010;Llarena and Kivistö, 2020), chicken liver pâté (Little et al, 2010;Moffatt et al, 2016;Lanier et al, 2018), and unpasteurized milk (Centers for Disease Control and Prevention (CDC), 2002; Burakoff et al, 2018).…”

Campylobacteriosis in Finland: Passive Surveillance in 2004–2021 and a Pilot Case-Control Study with Whole-Genome Sequencing in Summer 2022

“…In June–October 2022, 4.2% of examined flocks were Campylobacter positive, and during the rest of the year, 0.3% [ 36 ]. Previously, it has been estimated that one-fifth to one-third of domestic human cases in Finland might be related to consuming fresh chicken meat [ 20 , 37 ], even though the broiler flock prevalence is relatively low. In the EU, handling, preparing, and consuming broiler meat is estimated to cause 20–30% of human infections and around 50–80% of human campylobacteriosis cases might be attributed to the chicken reservoir in general, including by direct contact or via the environment [ 38 ].…”

Rapid and reliable detection of foodborne pathogens : Exploring Campylobacter ecology in enrichments to improve detection

“…Of all foods, poultry is recognized as the primary source of food-related transmission of Campylobacter to humans (Taylor et al, 2013) and (small) Campylobacter outbreaks regularly occur (Baker et al, 2020;Greig and Ravel, 2009;Lanier et al, 2018;Llarena and Kivistö, 2020). Poultry products are mainly contaminated with Campylobacter during industrial-sized slaughter and processing (Althaus et al, 2017;Boysen and Rosenquist, 2009;Melero et al, 2012;Zbrun et al, 2013).…”