S. suis serotype 2 meningitis in a patient with horse contact in a Japanese stable: A case report.

Overview

• This study reports a rare case of meningitis caused by Streptococcus suis serotype 2 in a stable worker in Japan who had contact with horses but no known exposure to pigs.
• The case highlights a potential new animal source for this zoonotic infection, traditionally linked to pigs, and underscores the need for further research on transmission from non-porcine animals.

Introduction to Streptococcus suis and Its Usual Sources

• Streptococcus suis is a gram-positive bacterium known to cause serious infections in humans, primarily meningitis.
• The pathogen is zoonotic, meaning it can be transmitted from animals to humans.
• Pigs are the primary reservoir and usual source of human S. suis infection.
• Infection typically occurs through direct contact with pigs or pig products, especially among farmers, abattoir workers, and butchers.
• Transmission routes from other animals have not been well established or documented prior to this case.

Case Presentation

• The patient was a 56-year-old Filipino man working in a Japanese horse stable.
• He had no known exposure to pigs but had frequent direct contact with horses due to his occupation.
• The patient sustained a head injury one month before hospital admission and subsequently developed fever and persistent headache, classic signs of meningitis.
• Cerebrospinal fluid (CSF) analysis was consistent with bacterial meningitis.
• Both blood and CSF cultures confirmed the presence of Streptococcus suis serotype 2, verifying the diagnosis.

Clinical Course and Complications

• The patient was treated with appropriate antibiotic therapy targeting S. suis.
• Despite treatment, he developed a brain abscess, a serious complication requiring surgical intervention via craniotomy.
• The patient experienced prolonged disorientation, indicating neurological impairment likely due to the infection and its complications.

Significance of the Case

• This is the first documented instance of S. suis meningitis suspected to originate from horse contact rather than pigs.
• The case challenges the existing understanding that pigs are the sole animal reservoir for S. suis infections in humans.
• It suggests that horses might serve as an alternative or additional source of infection, especially in individuals with occupational exposure.
• This finding opens new questions for epidemiological research to clarify whether horses can harbor and transmit S. suis to humans.
• Understanding these alternative transmission routes is critical for improving preventive measures and occupational safety guidelines.

Implications for Future Research and Public Health

• Calls for expanded surveillance of S. suis among various animal species beyond pigs, particularly horses.
• Necessitates investigations into the prevalence of S. suis carriage in horses and their potential role as reservoirs.
• Highlights the importance of educating people with horse contact about possible risks and symptoms of S. suis infection.
• May influence revisions in infection control practices in stables and related workplaces to mitigate zoonotic risks.
• Encourages clinicians to consider S. suis infection in meningitis patients with animal exposure histories beyond pigs.