Epidemiology, clinical manifestations, and outcomes of Streptococcus suis infection in humans

Abstract

Streptococcus suis, a bacterium that affects pigs, is a neglected pathogen that causes systemic disease in humans. We conducted a systematic review and meta-analysis to summarize global estimates of the epidemiology, clinical characteristics, and outcomes of this zoonosis. We searched main literature databases for all studies through December 2012 using the search term "streptococcus suis." The prevalence of S. suis infection is highest in Asia; the primary risk factors are occupational exposure and eating of contaminated food. The pooled proportions of case-patients with pig-related occupations and history of eating high-risk food were 38.1% and 37.3%, respectively. The main clinical syndrome was meningitis (pooled rate 68.0%), followed by sepsis, arthritis, endocarditis, and endophthalmitis. The pooled case-fatality rate was 12.8%. Sequelae included hearing loss (39.1%) and vestibular dysfunction (22.7%). Our analysis identified gaps in the literature, particularly in assessing risk factors and sequelae of this infection.

Keywords: Streptococcus suis; bacteria; bacterial meningitis; humans; meta-analysis; systematic review; zoonoses.

Figure 1

Flow diagram of the search and review process for this review of Streptococcus suis infection.

Figure 2

Global cumulative prevalence of Streptococcus suis infection through 2012.

Figure 3

Funnel plot showing evidence of publication bias among 26 studies in a meta-analysis of meningitis rates in Streptococcus suis infection. Each blue circle represents each study in the meta-analysis, forming an asymmetric funnel plot with a pooled log event rate (blue rhombus). Eight missing studies (red circles) added in the left side through the trim and fill method to make the plot more symmetric and gave an adjusted log event rate (red rhombus), which was lower than the original one.

Figure 4

Forest plot of subgroup meta-analysis (random effects) for the case-fatality rates by country reported in the 25 studies included in a review of Streptococcus suis infection. For each study, the event rate of the death outcome and 95% CI are presented, with size proportional to study weight. The red rhombus indicates the pooled event rate for each country group.

Figure 5

Meta-regression scatter plot showing the correlation between case-fatality rate and meningitis rate in a review of Streptococcus suis infection. The logit event rate was calculated for case-fatality rate as follows: logit event rate = ln[event rate/(1 − event rate)]. Each circle represents a study in the meta-analysis, and the size of the circle is proportional to study weighting. Studies with higher meningitis rates tended to report lower death rates.