Study on epidemiological characteristics of the Japanese Encephalitis in Ha Nam during 2001 - 2006

Background: Viet Nam is located in the epidemiological region of Japanese Encephalitis (JE). JE vaccine manufactured in Viet Nam has been used in the national vaccination program since 2003, but there has been no scientific study on the effectiveness of this program in Ha Nam province. Objectives: To investigate the epidemiology of JE and effectiveness of vaccinations in Ha Nam province from 2001-2006. Subjects and method: All residents in Ha Nam province, with the key focus group being JE cases. The retrospective and prospective epidemiological descriptive method was used. Results: The records of 148 cases of JE were collected. Among them, 42.5% (63 cases) were confirmed as JE by MAC-ELISA. The incidence and mortality rate were 1.29/100,000 and 0.12/100,000, respectively. Confirmed JE cases were found annually in all districts of Ha Nam province. However, it has been in decline, especially since the vaccination program was implemented for 1-5 year old children. The disease occurred in the summer with the peak in May and June (80.9% of total cases). Most of the cases were children under 15 years old (98.4%). The highest incidence rate was 6.4/100,000; 5.5/100,000 and 5.3/100,000 in the children aged 5-9, 1-4 and under 1 year old, respectively. Conclusion: The vaccination program appeared effective in reducing the mortality and morbidity of JE among children in Ha Nam province.

Study fluctuation and confirmation of Japanese encephalitis vector in Ha Nam province, 2006-2007 \r\n', u'\r\n', u'

Background: Japanese Encephalitis (JE) virus is a leading cause of encephalitis in children with high mortality and complication. JE is a dangerous infectious disease via Culex mosquitoes. Objective: To identify the density of some mosquitoes and vectors that transmit JE virus in Ha Nam province. Subject and Method:There were 30.333 mosquitoes including 05 genera and 15 species which were collected at night from April 2006 to March 2007 in the following communes: Tanson (midland area) Hungcong (plain area) and Liemchinh (suburban area). Results: A total of 06 Culex species, the highest rate is Culex tritaeniohychus (41.20%); Culex annulus (15.56%); other Culex species occupied around 0.15% -2.49%. In these communes, the density of Culex tritaeniohychus was higher than Culex annulus. They were found to be active all year round, but the highest density of Culex tritaeniohychus and Culex annulus is 5.86 and 2.15, respectively in April and fall to 4.35% and 1.71% in July. The collected mosquitoes during April, May, June and July includes 133 and 28 Culex tritaeniohychus and Culex annulus pools, respectively; all were to be processed for the isolation of Japanese Encephalitis (JE) virus. There were 12 Culex tritaeniohychus and 2 Culex annulus pools which were collected in Tanson commune yielding positive. Conclusion: The results were confirmed that Culex tritaenioohychus and Culex annulus are the major vectors that transmit JE virus in Ha Nam, 2006 - 2007. All 14 JE virus strains were isolated from collected mosquito pools during April, May and June; whereas JE virus strain was not yet isolated from collected mosquito pool in July. Thus, in order to control JE disease, it is necessary to control JE vectors in April, May and June.

Detection of Japanese encephalitis frequency in the pig population in Ha Nam province by GAC-ELISA

Background: Mosquitoes and pigs play important roles in maintaining and increasing the Japanese Encephalitis (JE) virus in nature and which is then transmitted to humans. Thus, surveillance of the JE infection frequency in the pig population may predict the human JE cases. \r\n', u'Objectives: The study aimed to determine IgG antibody against the JE virus in the pig population in Hanam province \r\n', u'Subjects and methods: The study included 1791 pig serum samples collected from 3 districts of Hanam province from Apr 2006 to Mar 2007. GAC-ELISA technique was used to determine the JE virus infection in the swine population.\r\n', u'Results: The average positive rate in pig population was 34.9 % (626/1791); with the highest frequency occurring in the summer (37.7%- 84.0 %), co-incident with the JE season in Northern Vietnam. On the contrary, in winter JE case are rare, frequency of IgG antibody against JE virus in the swine population was low, ranging from 9.2% to 22.0.%. \r\n', u'Conclusions: These results have shown the ecologically close relationship between the amplification of the JE virus in the swine population, vector and JE cases in northern Vietnam. \r\n', u'