Pathogenicity of Listeria monocytogenes Scott A after oral and oculonasal challenges of day-old turkey poults.

Listeria monocytogenes is a ubiquitous, environmental pathogen that has contaminated poultry ready-to-eat products resulting in large-scale recalls. Research is needed to determine the source of product and processing plant contamination with L. monocytogenes. The purpose of this study was to compare the oral and oculonasal routes of infection on the pathogenicity of L. monocytogenes in turkey poults under different housing conditions. One-day-old turkey poults were challenged by either route with the Scott A strain of L. monocytogenes and placed either in paper-lined battery-brooder cages for 1 wk or in floor pens on fresh pine-shaving litter. On day 7, birds challenged in battery cages were transferred to floor pens. Challenge by the oculonasal route resulted in higher mortality (P = 0.05) and lower body weights (P < 0.0001) compared with both nonchallenged controls and those challenged by the oral route. Birds contained in battery cages for 1 wk had higher mortality (P = 0.002) and higher body weights (P < 0.0001) compared with floor-pen-reared birds. Using direct plating, the challenge strain was isolated from the gall bladder, brain, and knee joint of only one dead poult challenged by the oculonasal route. These results suggest that day-old turkey poults may be more susceptible to an oculonasal challenge with L. monocytogenes than to an oral challenge and that containment in battery cages for the first week increased contact exposure to the challenge.