Some aspects of the epidemiology of equine salmonellosis.

This research investigated the occurrence of Salmonella bacteria in horse populations, with findings suggesting a high mortality rate and increased prevalence of specific Salmonella serotypes among affected horses.

Study Methodology

• The survey studied two horse populations to detect the presence of Salmonella, specifically looking for asymptomatic faecal excretors (horses that shed the bacteria without showing signs of illness).
• The researchers used a sample of 1201 faecal samples from 250 horses which were hospitalized at the University of Sydney.
• These samples were cultured (grown in controlled conditions) to identify the type and amount of Salmonella bacteria present.

Study Findings

• The study found three different types, called serotypes of Salmonella: S. typhimurium, S. anatum, and S. tennessee were discovered amongst 7 of the sampled horses, which equates to 2.8%.
• These bacteria were not detected in another sample tested from 75 mares at a thoroughbred stud farm.
• In retrospect, when considering past data, S. typhimurium was found to be the most common serotype (70%) amongst 171 horses with clinical salmonellosis seen at Camden from 1969 to 1986.
• Out of the forty cases analysed in detail since 1983, a high mortality rate of 60% was noted with an upsurge in cases due to S.bovis-morbificans.

Interpretation and Implications

• This study suggests that horse populations can harbour different types of Salmonella bacteria, with the most common type being S. typhimurium. S. bovis-morbificans is also highly associated with severe outcomes, represented in the high mortality rate.
• The absence of bacteria in the mares at the stud farm may indicate different factors influencing the presence of bacteria, such as environment, hygiene practices or exposure levels.
• The issue of horses developing salmonellosis while in a hospital setting raises concerns about the adequacy of infection control measures in these facilities and the possibility of horses being carriers of the disease without presenting any symptoms.