Comparative analysis of farming practices and the prevalence of Salmonella enteritidis in broiler chickens from small and large-scale farms within an 80 kilometre radius of Harare

Abstract

Non-typical Salmonella, particularly Salmonella enteritidis, is a major zoonotic pathogen. In Zimbabwe, small-scale poultry farms are a critical part of the food supply chain, yet their disease burden and husbandry practices are not well characterised, leading to public health risks. This study compared the prevalence of Salmonella enteritidis and farming practices between small-scale and large-scale broiler farms in the Harare metropolitan region. In a cross-sectional study, 1050 cloacal swabs were collected from 6-week-old broilers across 70 farms (35 small-scale, 35 large-scale) within an 80 km radius of the capital Harare. Samples were cultured and isolates confirmed serologically, with farming practices assessed using a checklist. Prevalence was calculated, and a generalized linear mixed model was used to determine association, accounting for farm-level clustering. The overall prevalence of Salmonella Enteritidis was 10.4% (95% CI: 8.6 – 12.2%), with small-scale farms having a significantly higher prevalence (17.7%) than large-scale farms (2.3%). After adjusting for farm-level clustering, broilers from small-scale farms had 18 times higher odds of infection (OR = 18.95% CI: 5.6 – 90.1, p< 0.001). This disparity was strongly associated with markedly inferior biosecurity protocols, limited veterinary supervision, and higher-risk management practices on small-scale farms. Small-scale broiler production systems near Harare are significantly more vulnerable to Salmonella Enteritidis contamination due to insufficient biosecurity and management practices. This highlights an immediate necessity for focused interventions, such as farmer education and enhanced support for biosecurity measures, to reduce zoonotic risks and improve food safety.