A review of Legionella pneumophila in horses and some South African serological results.

This study is about the investigation of Legionella pneumophila exposure in horses and some associated people in South Africa, revealing a much lower rate of exposure compared to what is seen in the United States and noting that horses are unlikely a source of infection, but both humans and horses are likely exposed from a shared source.

Research Objective and Method

• The primary purpose of the study was to analyze the prevalence of Legionella pneumophila, a type of bacteria, in a specific population of horses and the people who work closely with them in South Africa.
• Samples of serum, the liquid part of the blood, were obtained from a total of 329 horses and were tested for the presence of L. pneumophila antibodies. The presence of antibodies reveals that an individual has been exposed to the bacteria.
• The research also involved serological testing of individuals in close association with the sero-positive horse – implying the horse that tested positive for the bacteria – to further understand the transmission and the source of the bacteria.

Research Findings

• Out of 329 horse sera tested, almost 60% (192 out of 329) did not show any exposure to L. pneumophila.
• About 35% (114 out of 329) had low exposure (end-point titres of 1/2), about 7% (22 out of 329) had a slightly higher exposure (end-points of 1/16), while less than 1% (only one horse) had significant exposure (end point of 1/256).
• Consequently, the study found a significantly lower rate of exposure to the bacteria in South Africa compared to reports from the United States.
• Interestingly, among the 22 people in close association with horses tested, 3 individuals had an end-point titre of 1/64, and just one person displayed an end-point titre of 1/256. Such findings suggest that humans and animals are probably exposed to the bacteria from a common source, but it is not the horse.

Implication of the Findings

• The results of the study are important regarding the understanding of the exposure and prevalence of Legionella pneumophila in horses and humans in South Africa.
• The findings suggest that horses cannot be considered an infection source, leading to further research to discover the common infection source in the environment.
• This study’s findings provide a foundation for future research about the prevention and control of Legionella pneumophila infections associating humans and animals in the region.