Horizontal Spread of Human and Poultry-Derived Strains of Campylobacter jejuni among Broiler Chicks Held in Incubators and Shipping Boxes

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Abstract
The first chick to hatch and dry in each of a series of incubators was fed a suspension of Campylobacter jejuni via a stomach tube and returned to the incubator. Subsequently, all hatched chicks were taken out of the incubators and housed in standard transport boxes for a further 24 h, after which they were killed by carbon dioxide inhalation. The intestinal tracts of all hatched birds were excised, enriched in liquid media and then plated on media selective for C. jejuni. Campylobacters were cultured from up to 70% of the chicks but this percentage varied with the strain originally fed to the initial chick. The spread of poultry-derived strains was as extensive as that of some human-derived strains, while other human strains showed little tendency to spread amongst chicks. A significant number of hatched, healthy chicks had distended intestinal tracts and showed abnormal gross liver pathology. This symptom was typical of those strains of C. jejuni known to be invasive or toxigenic. However, the gross pathology occurred more frequently than did the incidence of viable C. jejuni in the intestine of the same chicks, suggesting either that the C. jejuni were now mainly unculturable or that some cellular product was responsible for the intestinal pathology. The serotype of each of the strains isolated, was identical to the serotype of the strain initially fed to each banded bird. This laboratory study shows that one infected chick in an incubator potentially can infect other chicks before the birds reached the farm in transport boxes, so accounting for a further source of C. jejuni contamination of poultry.