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A systematic review and meta-analysis of the sources of Salmonella in poultry production (pre-harvest) and their relative contributions to the microbial risk of poultry meat

Wang, J., S. Vaddu, S. Bhumanapalli, A. Mishra, T. Applegate, M. Singh and H. Thippareddi

Salmonella is a major foodborne pathogen related to the consumption of poultry meat and is the leading cause of salmonellosis. Salmonella is known to transmit in poultry flocks both vertically and horizontally. However, there is a lack of knowledge on the sources of Salmonella in poultry live production systems, including hatchery, feed, water, environment-interior, and -exterior. A systematic review- meta-analysis was conducted to quantify potential sources of Salmonella during pre-harvest and their relative contributions to microbial risk of poultry meat. After applying exclusion criteria, 16,800 studies were identified from Google Scholar, and 39 relevant studies were included in the meta-analysis for relative contributions to Salmonella positivity on broilers. From the identified studies,the number of positive samples and sample size were included as quantitative data. Regions of study conducted (U.S. and non-U.S.) and sample source (contribution factor) were extracted from the studies. Sources of samples from the broiler live production section were further divided into excreta (e.g., excreta or cecal samples, or cloacal swabs), litter (e.g., litter, boot socks, or drag swabs), chicks, hatchery, water, feed, interior environment (e.g., rodents, darkling beetles, fan surfaces, feed trough or mice), exterior environment (e.g., water puddles, wild birds, soil, grass, or poultry house outside surface swabs). A generalized linear mixed model approach combined with logit transformation was used to stabilize the variance. Data analysis was conducted using R version 4.0.2 (R Core Team, 2021). Meat for package was used to generate the meta-analysis statistics (predicted prevalence and heterogeneity parameters) and Forest plots. The hatchery was the most significant contributor of Salmonella, with a prevalence of 48.5% (95% CI: 32.8 to 64.5%). Litter, feces, and the poultry house’s internal environment were the three other major contributing factors, with a prevalence of 25.4 (95% CI: 16.6 to 37.0%), 16.3 (95% CI: 10.6 to 24.3%) and 7.9% (95% CI: 3.0 to 18%), respectively. Poultry house external environment (4.7%), feed (4.8%), chicks (4.7%), and drinker water also contributed to Salmonella in the poultry environment.

Results from this meta-analysis can inform poultry producers and processors to implement control strategies to minimize the risk of foodborne illness from Salmonella related to the consumption of poultry and poultry products. These strategies include eliminating the sources of Salmonella and incorporating interventions in live production to reduce Salmonella concentrations in broilers.