Streptococcus suits serotype 2 outbreak at Chomthong District, Chiangmai Province, June-July, 2008

Abstract

              At out-patient department of Chomthong hospital, Chiangmai, 2 suspected cases of Streptococcus suis were reported on June 29th, 2008, 4 days later, 7 more cases came with headache, myalgia and hearing loss. Surveillance rapid response team (SRRT) of Chomthong hospital together with SRRT from Chiangmai Provincial Public Health Office and Department of Epidemiology, Ministry of Public Health started the investigation on July 5th, 2008. The objectives were: to verify diagnosis and confirm existence of the outbreak, to explain the epidemic by time, place, and person, to find source of infection and route of transmission, and to perform control measure. Long term complication of the infection was also evaluated. Descriptive epidemiological study among the population who lived in Chomthong  district during June 24th-July 10th, 2008 was performed by using Streptococcus suis report form (SS1) and  Streptococcus suis investigation form (SS2). Among 265 populations at risk, 62 cases were found; the attack rate was 23.4 %. Male to female ration was 3.4:1, the highest number of cases was among 41-50 year age group, mean was 37.1 years (range 19-85 years). The highest cases was among labor group (64.5 %) and 69.4 % had the history of eating raw pork meat and 51.6 % were alcohol drinkers. The most common symptoms were vertigo (93.5 %) and fever (83.9 %). 15 cases (24.4 %) had hearing loss however 4 cases (26.7 %) returned to be normal after 6 months. The epidemic curve was shown to be common source outbreak. The first case was found on June 27th while the last case was found on July 9th. The shortest incubation period range from 1-9 days (median= 2.4 days). The cases distributed among 5 sub-districts, with the highest attack rate at Sobtea (33.0/100,000 population). The specimen from hemoculture, cerebrospinal fluid, and fluid from joints discovered Streptococcus suis serotype 2 that was virulent strain. Definite source of infection could not be identified. Alcohol drinking (OR= 6.03; 95% CI = 2.25<OR<10.15) and buying pork meat from shop A (OR = 4.26; 95% CI = I .15<ORK15.74) were found to related to disease outcome significantly (p-value<0.05). For control measure, war room was set to analyze the situation, plan for treatment, and to prevent and control the epidemic. Active case finding was done together with giving information to avoid eating raw pork blood and meat. Psychological support among the patients and relatives were done by the team from Suan Prung psychiatric hospital. The environmental study was performed to investigate the source of infection and how about the movement of the pigs before coming to the slaughterhouse. Nasal swab and tonsil swab of the pigs from the supply farm and also chopping boards swab were done. The slaughterhouse was cleaned by using detergent and chlorine. Surveillance among the pigs before sending to the slaughter house was strongly recommended. Active surveillance was applied until July 28th, 2008 and no more case was reported. The occurrence of Streptococcus suis demonstrates that the behavior of eating raw blood and pork meat in the community still be existed and need continuous campaign to stop the risk behavior.