Dairy Cattle, a Potential Reservoir of Human Campylobacteriosis: Epidemiological and Molecular Characterization of Campylobacter jejuni From Cattle Farms

Abstract

<i>Campylobacter jejuni</i> is a major foodborne pathogen that is increasingly found worldwide and that is transmitted to humans through meat or dairy products. A detailed understanding of the prevalence and characteristics of <i>C. jejuni</i> in dairy cattle farms, which are likely to become sources of contamination, is imperative and is currently lacking. In this study, a total of 295 dairy cattle farm samples from 15 farms (24 visits) in Korea were collected. <i>C. jejuni</i> prevalence at the farm level was 60% (9/15) and at the animal level was 23.8% (68/266). Using the multivariable generalized estimating equation (GEE) model based on farm-environmental factors, we estimated that a high density of cattle and average environmental temperature (7 days prior to sampling) below 24°C affects the presence and survival of <i>C. jejuni</i> in the farm environment. Cattle isolates, together with <i>C. jejuni</i> from other sources (chicken and human), were genetically characterized based on analysis of 10 virulence and survival genes. A total of 19 virulence profile types were identified, with type 01 carrying eight genes (all except <i>hcp</i> and <i>virB11</i>) being the most prevalent. The prevalence of <i>virB11</i> and <i>hcp</i> was significantly higher in isolates from cattle than in those from other sources (<i>p</i> < 0.05). Multilocus sequence typing (MLST) of <i>C. jejuni</i> isolates from three different sources mainly clustered in the CC-21 and CC-48. Within the CC-21 and CC-48 clusters, cattle isolates shared an indistinguishable pattern with human isolates according to pulsed-field gel electrophoresis (PFGE) and <i>flaA</i>-restriction fragment length polymorphism (RFLP) typing. This suggests that CC-21 and CC-48 <i>C. jejuni</i> from dairy cattle are genetically related to clinical campylobacteriosis isolates. In conclusion, the farm environment influences the presence and survival of <i>C. jejuni</i>, which may play an important role in cycles of cattle re-infection, and dairy cattle represent potential reservoirs of human campylobacteriosis. Thus, environmental management practices could be implemented on cattle farms to reduce the shedding of <i>C. jejuni</i> from cattle, subsequently reducing the potential risk of the spread of cattle-derived <i>C. jejuni</i> to humans through the food chain.