Salmonella Oranienburg isolated from horses, wild turkeys and an edible home garden fertilized with raw horse manure.

This research documents a case of Salmonella Oranienburg infection in a Northern California farm, focussing on the spread of the bacteria from horses to other animals and soil in the farm. The study emphasizes the risks of using raw animal manure as fertilizers and the necessity to educate the public about the associated food safety hazards.

About the Research

• The investigation began in July 2010 when a horse from a rural farm in coastal Northern California was diagnosed with Salmonella Oranienburg infection. This prompted an extensive environmental sampling in the farm to track the prevalence and source of the Salmonella infection.
• The research spanned from August 2010 to March 2011 during which various clinical and environmental samples were collected and cultured for salmonella detection.
• The samples included those from horses, a pet dog, water from horse troughs, manure storage pile composites, wild turkey faeces, and soil samples from the family’s garden.
• Salmonella was detected in several samples, indicating a widespread dissemination in the farm environment after the equine infection.

Main Findings

• Salmonella spp. was found in six out of eight horses, a pet dog, water samples from horse troughs, manure storage pile composites, wild turkey faeces, and soil samples.
• A total of 204 samples were analysed and the prevalence of Salmonella was distinct across different types of samples. It was particularly high in horses and manure storage piles.
• All tested samples showed the presence of S. Oranienburg with a PFGE pattern that matched perfectly with the horse clinical strain. This established the link between the horse infection and the widespread presence of the bacteria in the farm environment.

Implications

• The findings suggest that raw horse manure used as fertilizer was the most likely source of garden soil contamination.
• It was found that S. Oranienburg persisted in garden soil for an estimated 210 days, which is notably longer than the 120-day standard currently required by the National Organic Program. This points to the need for reviewing the existing standards.
• The study also highlights the potential role of wild turkeys in spreading the bacteria, although further research is needed to establish this connection.
• Overall, this study stresses on the potential risks of using raw animal manure as fertilizers in edible gardens and calls for public education on food safety hazards associated with such practices.