An outbreak of equine neonatal salmonellosis.

This study investigates an occurrence of Salmonella Ohio infection, a rare type of salmonellosis, in foals less than 8 days old on a large Thoroughbred farm in California. The researchers found that the mares, although asymptomatic, were likely transmitting the bacteria to the foals. After enforcing control measures, while foals continued to be infected, none fell ill.

Study Context and Objective

• The research was conducted following an outbreak of salmonellosis in foals in a Thoroughbred farm in California.
• The objective of the study was to identify the nature of this unusual outbreak, trace its source, and find relevant solutions.

Findings and Observations

• The primary symptom of this infection in foals was depression, anorexia, and diarrhea, and it was notably virulent, causing three foals to die from septicemia.
• The causative agent was discovered to be Salmonella ohio, a strain that is rarely involved in equine salmonellosis.
• Disease tests revealed that 27.8% of mares and 35.1% of foals were found to be infected with S. ohio, despite only the foals showing symptomatic signs.

Source of Infection and Transmission

• The mares were considered the source of the outbreak, transmitting the infection to their newborn foals.
• The lack of symptoms in the mares was implied to have facilitated environmental infection through unnoticed contagion.

Control Measures and Outcomes

• Once disease control measures were implemented, there was still evidence of foals contracting the infection, however, they did not exhibit symptoms or fall ill.
• The research indicates that Salmonella serotypes, even those that are traditionally low in virulence, such as S. ohio, have the potential to cause serious disease outbreaks.

Implications and Conclusion

• The findings of the study highlight the risk that asymptomatic carriers pose in the spread of infectious diseases, especially in a closed population like a horse farm.
• This research underscores that effective infection control and preventive measures can significantly mitigate disease outbreaks, even in the presence of ongoing transmission.
• This anomaly of Salmonella Ohio causing an outbreak adds to the scientific understanding that serotypes, despite their perceived virulence level, can still pose serious health risks.