Listeria monocytogenes in horses in Iceland.

This research paper investigates the occurrence of the Listeria monocytogenes bacteria in horses in Iceland and assesses its potential spread through faeces and grass silage.

Study Objectives and Methods

• The researchers aimed to evaluate cases of listeriosis, a bacterial infection, in horses in Iceland caused by the Listeria monocytogenes bacteria.
• Twenty isolates of the bacteria, linked to five confirmed and four suspected incidents of listeriosis, were characterized using serotyping, pulsed-field gel electrophoresis, and ribotyping.
• Semiquantitative estimates were also made on the numbers of Listeria monocytogenes in faeces from horses showing signs of listeriosis and in grass silage that they were fed.

Main Findings

• Large counts of Listeria monocytogenes were frequently found in the faeces of horses with severe disease symptoms.
• The twenty isolates could be divided into six distinct genotypes, and each incident involved only a single genotype indicating that each outbreak was likely caused by one strain of bacteria.
• One particularly prevalent serovar 1/2a genotype was linked to three confirmed cases of listeriosis in 1991, 1993, and 1997.
• An important observance was that the same genotype resulted in disease in one horse and was also isolated from the spoiled grass silage that the horse had consumed. This finding points to a potential source of infection.

Implications of the Study

• The research highlights the pervasiveness of Listeria monocytogenes in horses in Iceland, specifically how it likely spreads via faeces and possibly completes its life cycle through contaminated grass silage.
• This study helps in better understanding the epidemiology of equine listeriosis and may inform future strategies to control and prevent the spread of Listeria monocytogenes in horse populations.