Epidemiology of Streptococcus suis infection in Viet Nam

Ho Dang Trung Nghia (2011). Epidemiology of Streptococcus suis infection in Viet Nam. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.000118dd

Abstract

Human Streptococcus suis infection is an emerging zoonotic disease in Southeast Asian countries. It can seriously threaten human heath causing both outbreaks with high morbidity and mortality and endemic disease. It can also have a major negative impact on the economically important pig industry across the region. The aims of this thesis were to understand the epidemiology of human S. suis infection in Viet Nam, focusing on the incidence rate, seasonality and risk factors for infection with S. suis.

I conducted a prospective surveillance of central nervous system (CNS) infections in twelve provinces of Viet Nam including the Central, the Highlands and the south of the country. I was able to demonstrate that S. suis was an endemic disease across southern Viet Nam, and responsible for 49% of adult purulent bacterial meningitis. The incidence rate was 0.57 per 100,000 adult person-years (95% CI, 0.47-0.70) and infection had a case fatality rate of 8%. S. suis meningitis tended to predominantly occur in the hottest months of the year in central Viet Nam, but this
seasonal pattern was not documented in the south of the country.

A case control study demonstrated that occupational exposure to pigs or pork was a significant risk factor for S. suis infection. I was also able to identify novel and important risk factors for S. suis disease among the Vietnamese population. Eating fresh blood and undercooked pig products (OR1 = 2.22; 95%CI = [1.15-4.28] and OR2 = 4.44; 95%CI = [2.15-9.15]) and exposures of people with skin injuries to pigs or pork (OR = 7.48; 95% CI = [1.97-28.44] and OR2 = 15.96; 95%CI = [2.97-85.72]), were significant risk factors. These risk factors can be addressed in health education programs targeted at individuals and communities at risk, focusing on skin protection for those in direct contact with pigs or pork and avoiding eating fresh blood and undercooked pig products. In addition, we were unable to detect S. suis serotype 2 DNA from the throat and rectal swab samples of 1523 healthy persons and non-S. suis infected patients, including those with exposure to pigs and pork meat. Hence I was not able to demonstrate human carriage of S. suis serotype 2 in the Vietnamese population.