role of starlings in the spread of Salmonella within concentrated animal feeding operations

1. Characterizing and mitigating the disease risks associated with wildlife use of concentrated animal feeding operations (CAFOs) can reduce the spread of micro-organisms throughout the environment while increasing agricultural productivity. To better understand the disease risks associated with bird use of CAFOs, we assessed the capacity of European starlings Sturnus vulgaris to spread Salmonella enterica to cattle, their feed and water. 2. We sampled starlings, cattle feed, cattle water and cattle faeces from 10 CAFOs in Texas, USA. Samples were screened for Salmonella enterica to investigate: (i) the prevalence of S. enterica in starlings using CAFOs, (ii) whether there was a relationship between cattle infections and starling numbers, and (iii) if S. enterica contamination of cattle feed and water was related to numbers of starlings observed on CAFOs. 3. We used generalized linear mixed logistic regression models to assess the importance of starlings, cattle stocking, facility management and environmental variables in the transmission of S. enterica to cattle, feed troughs and water troughs in CAFOs. 4. Starling gastrointestinal tract samples tested positive for S. enterica (2·5% prevalence; 95% CI = 0·3%, 8·6%) and starlings were retained as model covariates in the best supported logistic regression models for S. enterica contamination within cattle feed, water and faeces. 5. Salmonella enterica contamination of both cattle feed troughs and water troughs is significantly related to numbers of starlings. Contamination in cattle feed increased as more starlings entered feed troughs. Contamination in water troughs increased asymptotically as numbers of starlings on CAFOs increased. Starling variables in the cattle faecal shedding model were not significant. 6. Synthesis and applications. The numbers of European starlings better explained S. enterica contamination of cattle feed and water than other variables including cattle stocking, facility management and environmental variables. This suggests that starlings are a source of S. enterica contamination in CAFOs. Thus, starling management tools such as population control, habitat management, exclusionary devises and bird repellents may be used to reduce the amplification and spread of disease within livestock production systems.