Comparison of Potential Salmonella Portals of Entry and Tissue Distribution Following Challenge of Poultry

The following studies evaluated our hypothesis that transmission by the fecal-respiratory route may be a viable portal of entry for Salmonella and could explain some clinical impressions of relatively low-dose infectivity under field conditions in relation to the requisite high oral challenge dose that is typically required for infection of poultry through the oral route in laboratory studies. Initial field reports indicating tracheal sampling to be a sensitive tool for monitoring Salmonella infection in commercial flocks, suggested that tracheal contamination could be a good indicator of Salmonella infection under commercial conditions. Further, a usual assumption regarding airborne Salmonella reaching the upper respiratory tract, would ultimately involve oral ingestion, due to the presence of the mucociliary clearance was evaluated. Suspension in 1% mucin failed to increase the infectivity at any dose of Salmonella when compared to OR administration without mucin and intratracheal (IT) challenge, which was also recovered from lung tissue. IT administration was more effective or at least as effective at colonizing the ceca of 7d chickens, suggesting that the respiratory tract may be an overlooked potential portal of entry for Salmonellae. Finally, the hypothesis was evaluated through IT administration of Salmonella, in comparison with oral administration. A significantly higher or equivalent cecal recovery of Salmonella, with a clear dose response curve, with the IT groups as compared to groups challenged OR, added further support to the hypothesis. Both the cecal CFU recovery data and organ invasion incidence data from these experiments provided evidence for the subsequent fate of Salmonella exposed to the respiratory system, potentially involving a systemic route. Overall, our data suggests that the respiratory route might be a viable portal of entry for Salmonella in poultry. Clarification of the potential importance of the respiratory tract for Salmonella transmission under field conditions may be of critical importance as efforts to develop intervention strategies to reduce transmission of these pathogens in poultry continue

Evaluation of respiratory route as a viable portal of entry for Salmonella in poultry

Gopala Kallapura,1 Xochitl Hernandez-Velasco,2 Neil R Pumford,1 Lisa R Bielke,1 Billy M Hargis,1 Guillermo Tellez1 1Department of Poultry Science, University of Arkansas, Fayetteville, AR, USA; 2College of Veterinary Medicine and Animal Husbandry, The National Autonomous University of Mexico, Mexico Abstract: With increasing reports of Salmonella infection, we are forced to question whether the fecal–oral route is the major route of infection and consider the possibility that airborne Salmonella infections might have a major unappreciated role. Today's large-scale poultry production, with densely stocked and enclosed production buildings, is often accompanied by very high concentrations of airborne microorganisms. Considering that the upper and lower respiratory lymphoid tissue requires up to 6 weeks to be fully developed, these immune structures seem to have a very minor role in preventing pathogen infection. In addition, the avian respiratory system in commercial poultry has anatomic and physiologic properties that present no challenge to the highly adapted Salmonella. The present review evaluates the hypothesis that transmission by the fecal–respiratory route may theoretically be a viable portal of entry for Salmonella in poultry. First, we update the current knowledge on generation of Salmonella bioaerosols, and the transport and fate of Salmonella at various stages of commercial poultry production. Further, emphasis is placed on survivability of Salmonella in these bioaerosols, as a means to assess the transport and subsequent risk of exposure and infection of poultry. Additionally, the main anatomic structures, physiologic functions, and immunologic defense in the avian respiratory system are discussed to understand the potential entry points inherent in each component that could potentially lead to infection and subsequent systemic infection of poultry by Salmonella. In this context, we also evaluate the role of the mucosal immune system as essentially one large interconnected network that shares information distally, since understanding of this sort of communication between mucosal sites is fundamental to establish the next phase of disease characterization, and perhaps immunization and vaccine development. Further characterization of the respiratory tract with regard to transmission of Salmonella under field conditions may be of critical importance in developing interventional strategies to reduce transmission of this important zoonotic pathogen in poultry. Keywords: Salmonella, respiratory route, portal of entry, systemic disseminatio

Probiotics for Human and Poultry Use in the Control of GastrointestinalDisease: A Review of Real-World Experiences

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