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.S treptococcus suis is a neglected zoonotic pathogen that has caused large outbreaks of sepsis in China (1,2) and has been identified as the most common and the third leading cause of bacterial meningitis in adults in Vietnam and Hong Kong, respectively (3-5).S. suis infection is acquired from pigs, either during slaughtering or by handling and eating undercooked pork products.It is potentially preventable (3,6).Epidemiology of the infection differs between Western and Asian regions (7), and the role of high-risk eating habits (i.e., ingesting raw or undercooked pig parts, including pig blood, organs, and meat) in some Asian communities recently has been recognized (6,8,9).Rates of S. suis infection are low in the general populations of Europe and North America, and cases are concentrated among occupationally exposed groups, including abattoir workers, butchers, and pig breeders (10,11).In a 2009 review, ≈700 S. suis infections were reported worldwide by 2009, mostly from China and Vietnam (12).Clinical characteristics of this infection have been reviewed (12,13) and include meningitis, sepsis, endocarditis, arthritis, hearing loss, and skin lesions.Treatment of S. suis infection requires ≈2 weeks of intravenous antimicrobial drugs (12).The death rate varies, and deafness is a common sequela in survivors.Although substantial new data on the incidence, clinical and microbiological characteristics, and risk factors for S. suis infection have accumulated during recent years, the prevalence of this infection has not measurably decreased.We conducted a systematic review and metaanalysis to update the evidence and summarize the estimates of epidemiologic and clinical parameters to support practitioners' and policy makers' efforts to prevent and control this infection.