A systematic review and meta-analysis of the effectiveness of biosecurity and vaccination in reducing Salmonella spp. in broiler chickens

Our objective was to estimate the effectiveness of vaccination and biosecurity on the prevalence of Salmonella spp. in broiler chickens using systematic review and meta-analysis. A comprehensive search of the global primary literature was conducted in: Current Contents (1999–2009), Agricola (1924–2009), MEDLINE (1860–2009), Scopus (1960–2009), CAB (1913–2009), and Centre for Agricultural Bioscience Global Health (1971–2009). The search algorithm was (Salmonell*) AND (chicken* OR chick* OR poultry* OR broiler* OR gallus*). Additional studies were identified by contacting five topic experts and hand-scanning bibliographies of recent review articles and a recently published textbook. Studies were included if they were English language and investigated the effects of vaccination and biosecurity on the prevalence of Salmonella spp. in broiler chickens. All study design types were included. Data extraction and methodological assessment were conducted by two reviewers independently. All meta-analyses were based on random-effects models. For biosecurity, sixteen challenge studies (n = 137 treatment-control comparisons) and one controlled study (n = 2) met the inclusion criteria. Significant heterogeneity (Cochran's Q-statistic, p < 0.001) was observed among biosecurity challenge studies examining hydrogen peroxide or polyhexamethylenebiguanide hydrochloride applied to hatching eggs, making it inappropriate to present a summary effects measure. For vaccination, 19 challenge studies (n = 226) and three controlled studies (n = 10) met the inclusion criteria. Among live Salmonella Typhimurium vaccine challenge studies heterogeneity was not significant (p = 0.138). Vaccination with a live Salmonella Typhimurium reduced the risk of Salmonella cecal colonization in the treated broiler group by 35 out of 1000 broilers when compared to the control group (OR = 0.21; 95% CI = 0.06–0.77) and this effect was significant (p = 0.018). One biosecurity study (n = 2 treatment-control comparisons) and three vaccination studies (n = 10) were conducted in a commercial setting. The two included studies in the vaccination meta-analysis were both conducted at research facilities. The live Salmonella Typhimurium vaccine showed the most promise in reducing the prevalence of Salmonella in broiler ceca. However, the meta-analysis included few studies, and these studies challenged the birds with different serotypes. We recommend that more large-scale randomized, blinded trials be conducted with a live Salmonella Typhimurium vaccine on commercial farms.