ABSTRACT
Introduction: Salmonella Enteritidis and S. Typhimurium are the two most clinically important zoonotic Salmonella serovars and vaccination of breeding and laying hens affords effective Salmonella control. The use of live vaccines has proven beneficial for a number of reasons, including ease of application, protection from the first day of life onwards and initiation of a strong local immune response. Live vaccines can be applied in the drinking water from the first day of life onwards, but some rearers choose to wait until the end of the first week to ensure sufficient water consumption. However, this practice leaves the birds unprotected during the crucial first week of life, where they are most susceptible to colonization by field strains. The aim of this study was to determine if successful vaccine uptake is achieved when layer pullets are vaccinated as early as day one. Methods: Three pullet flocks were vaccinated at 1, 2, 3 or 5 days-of-age with AviPro™ Salmonella DUO, a live vaccine containing attenuated strains of S. Enteritidis and S. Typhimurium (Elanco Animal Health, Cuxhaven, Germany). The vaccine was administered via the drinking water following manufacturer's instructions. Two days post-vaccination, 10 birds per flock were culled and caecal and liver samples taken, along with two pools of faeces per flock. Levels of vaccine strains were determined by quantitative and qualitative bacteriology. Results: Vaccine strains were detected in all birds from all age groups indicating successful uptake of the vaccine. Levels of the S. Enteritidis vaccine were higher than levels of the S. Typhimurium vaccine, with the latter frequently only detectable following enrichment. There was an inverse correlation between age and caecal levels of vaccines, with the highest numbers seen in birds vaccinated at 1-day-of-age. Interestingly, S. Enteritidis vaccine strain levels in liver samples were highest when birds were vaccinated at 5 days-of-age. Discussion: These results show that successful uptake of both vaccine strains was evident in all age groups. The earlier the chicks were vaccinated, the higher the vaccine levels in caecal contents. We therefore recommend vaccination of pullets as early as practicably possible to ensure protection against exposure to field strains.
ABSTRACT
Ammunition and fishing weight usage is the greatest largely unregulated contributor of lead (Pb) deposition to the European environment. While the range of negative impacts of Pb exposure to humans and avian wildlife are relatively well documented, little is known about risks to wild mammals despite recent scientific interest and publications. A qualitative risk assessment of the potential Source-Pathway-Receptor linkages for European mammal exposure was conducted, based on literature reviews and existing evidence and discussions with experts from the fields of wild mammal feeding ecology, behaviour and health. The assessment identified 11 pathways for mammal exposure to Pb, with all 243 European species likely to be potentially exposed via one or more of these. All species were identified as potentially exposed via ingestion of water with elevated Pb from degraded ammunition/fishing weights. Ingestion of vegetation with elevated Pb from degraded ammunition/fishing weights potentially exposed many species (158), 78% of which had a potentially high risk of exposure when feeding in areas of high Pb deposition. Ingestion of retained ammunition in previously shot prey and/or discarded kill/gut piles with embedded ammunition was another significant pathway, contributing to predatory and scavenging carnivorous mammal exposure where an individual exposure event would be expected to be high. The mechanisms by which Pb from ammunition and fishing weight sources are moved up trophic levels and 'transferred' from areas of high deposition into wider food chains e.g. via water, flying invertebrates and herbivores being subsequently preyed upon requires further investigation. In conclusion, there are multiple and diverse Source-Pathway-Receptors linkages for European mammal exposures to Pb and evidence of exposure, from Europe and elsewhere, exists for some herbivores, carnivores, omnivores and insectivores. Both fatal but more likely non-fatal chronic and acute exposures may be expected to occur in wild European mammalian species, including those in poor conservation status.