Purpose: This study sought to identify specific meteorological factors affecting the presence and population levels of generic Escherichia coli (as an indicator for fecal contamination) in an integrated dairy and crop farm.
Methods: Over 14 months, environmental samples were collected from locations within an integrated dairy and vegetable crop farm, and enumerated for generic E. coli. Local weather factors were evaluated for their association with the presence of generic E.coli by using logistic regression and classification trees. In addition, negative binomial regression and regression tree method were applied to identify factors affecting population levels of generic E. coli from a sample location.
Results: The logistic regression and classification tree identified monthly precipitation (OR=4.4, P < 0.0001) and monthly temperature (OR=1.1, P < 0.0001) as risk factors, indicating that the probability of isolation of generic E. coli increases with an increasing average amount of rain (>1.42 mm) and increasing average temperature (>20.2°C) in the previous 30 days. However, probability of isolation was negatively correlated with rainfall amount within 2 days of sampling (P < 0.0001). In addition, according to the negative binomial model and regression tree, generic E. coli populations decreased with increasing rainfall and wind speed in the previous 2 days, suggesting that recent rainfall (>0.51 mm) and high wind speed (>2.53 m/s) may lower generic E. coli population levels within farm environments.
Significance: Results suggest that presence and population levels of E. coli on integrated dairy/vegetable farms is influenced by temperature, precipitation and wind speed. Meteorological factors should be considered when evaluating farm management practices to reduce pre-harvest pathogen contamination.