Japanese viral encephalitis

One of the leading causes of acute encephalopathy in children in the tropics is Japanese encephalitis (JE). Transmitted by the culex mosquito, this neurotropic virus predominately affects the thalamus, anterior horns of the spinal cord, cerebral cortex, and cerebellum. It mainly affects children <15 years and is mostly asymptomatic. The occasional symptomatic child typically presents with a neurological syndrome characterised by altered sensorium, seizures, and features of intracranial hypertension. Aetiological diagnosis is based on virus isolation or demonstration of virus specific antigen or antibodies in the cerebrospinal fluid/blood. Though no antiviral drug is available against JE, effective supportive management can improve the outcome. Control of JE involves efficient vector control and appropriate use of vaccines.     

Isolated involvement of substantia nigra in Japanese encephalitis

A 16-year-old boy presented with febrile encephalopathy with meningeal signs, abnormal eye movements and extrapyramidal features. Clinical impression was meningo-encephalitis due to infective aetiology. He was diagnosed as a case of Japanese encephalitis. MRI brain revealed bilateral, symmetrical hyperintensities of substantia nigra. This neuro-imaging finding is very rarely reported in Japanese encephalitis.     

Transmission of Japanese encephalitis virus in Hong Kong

1. Pigs are likely to be the main amplifying host for Japanese encephalitis virus. 2. The success of a swine vaccination programme depends on the timing of the loss of maternal antibody protection and seasonal dynamics of the vector population. 3. Vaccination may be ineffective in the face of strong natural infection because of the variability in timing of the loss of maternal antibody protection.4. Evidence in support of swine vaccination as a human health intervention was not found.     

乙脑疫苗研究进展

目的 乙脑病毒(JEV)灭活疫苗应用以来，乙型脑炎的发病率大大下降，但由于它存在一些缺点，即(1)需多剂接种才能产生良好的免疫效果，(2)不良反应渐多如局部反应率达20％左右，全身反应率达10％，(3)价格昂贵，生产工艺复杂等影响其进一步推广。目前研究新的疫苗有两类，第一为减毒活疫苗，由SAl4衍生出的系列病毒株SAl4-14—2，SAl4—2—8，SAl4—5—3等皆证实毒力低，安全性好。对其核苷酸序列分析表明E138位(谷氨酸→赖氨酸)，E176(异亮氨酸→缬氨酸)可能是引起减毒的位点。第二为基因重组疫苗。IC47为无毒重组的JEV。动物实验证明它具有活性，无毒性，且一次注射就会使机体免疫保护能力大大提高，分子生物学证实它是E138位点的单点突变引起，因此IC47做为正规疫苗应用之前，须解决稳定剂型、清除毒力逆转的问题。     

用生物反应器制备乙脑灭活疫苗的研究

目的 用生物反应器制备乙脑纯化灭活疫苗.方法 用搅拌式生物反应器培养Vero细胞,接种并培养乙型脑炎病毒,将收获的病毒液进行灭活和纯化.结果 细胞密度都增至2.4×106ml-1以上,病毒滴度都>7.25 lgLD50/ml.结论 用生物反应器制备乙脑灭活纯化疫苗的工艺合理,可以生产出高滴度的乙型脑炎病毒液.     

甘肃省流行性乙型脑炎地区分布特征分析

目的分析甘肃省1990—2008年流行性乙型脑炎（乙脑）的地区分布特征,为控制乙脑提供依据。方法运用描述流行病学方法,利用甘肃省疾病预防控制中心（CDC）历年疫情资料汇编和法定传染病报告系统资料,分析1990～2008年甘肃省乙脑地区分布特征。结果1990～2008年,兰州及以西的6个市无病例,天水、陇南、平凉3市,是甘肃省乙脑发病最高的市,近19年年均发病率〉1／10万,在14个市州乙脑发病率排序中一直位居前3位,每年乙脑病例数占全省乙脑病例总数95％左右。结论甘肃省乙脑病例主要集中在东南部地区,兰州以西无乙脑病例报告,天水、陇南、平凉3市是甘肃省的主要疫区。     

流行性乙型脑炎病毒研究进展

流行性乙型脑炎病死率较高，后遗症严重，在亚洲地区危害较大。本文就乙脑病毒的分类、抗原特性、对细胞和动物敏感性、基因组的结构特征、毒力基因、基因分型和疫苗等方面的研究进展作一综述。     

Japanese encephalitis in an Australian soldier returned from Vietnam.

An imported case of Japanese encephalitis is reported and discussed. Recent literature on the clinical aspects of the disease is reviewed. Although the disease is unlikely to become a problem in Australia, it will remain a serious hazard to nonimmune personnel moving into an endemic area.     

Japanese encephalitis in north Queensland, Australia, 1998.

OBJECTIVE: To describe the circumstances of two cases of Japanese encephalitis (JE) in north Queensland in 1998, including one acquired on the Australian mainland. DESIGN: Serological surveillance of sentinel pigs for JE virus activity; serological surveys of humans and pigs and viral cultures of mosquito collections. SETTING: Islands in the Torres Strait and communities in the Northern Peninsula Area (NPA) and near the mouth of the Mitchell River in Cape York, Queensland, in the 1998 wet season (December 1997-May 1998). RESULTS: Sentinel pigs in the Torres Strait began to seroconvert to JE virus in February 1998, just before onset of JE in an unvaccinated 12-year-old boy on Badu island. By mid-April, most sentinel pigs had seroconverted. Numerous JE viruses were isolated from Culex annulirostris mosquitoes collected on Badu. In early March, a person working at the mouth of the Mitchell River developed JE. Serological surveys showed recent JE virus infection in 13 young pigs on a nearby farm, but not in 488 nearby residents. In NPA communities, sentinel pigs seroconverted slowly and JE viruses were isolated from three, but none of 604 residents showed evidence of recent infection. Nucleotide sequencing showed that 1998 JE virus isolates from the Torres Strait were virtually identical not only to the 1998 isolate from an NPA pig, but also to previous (1995) Badu isolates. CONCLUSIONS: JE virus activity was more widespread in north Queensland in the 1998 wet season than in the three previous wet seasons, but ecological circumstances (e.g., less intensive pig husbandry, fewer mosquitoes) appear to have limited transmission on the mainland. Nucleotide sequencing indicated a common source for the 1995 and 1998 JE viruses. Circumstantial evidence suggests that cyclonic winds carried infected mosquitoes from Papua New Guinea.     

Monitoring of malaria,Japanese encephalitis and filariasis vectors

Background

Vector monitoring in military stations would help in protecting the armed forces from vector borne diseases such as malaria, Japanese encephalitis and filariasis.

Methods

Adult mosquitoes were collected from four villages around a military station in India using light traps and the species composition was estimated. Insecticide susceptibility of disease vectors against DDT, deltamethrin and permethrin was established using WHO kits.

Results

The known malaria vectors constituted 4.9% of the total mosquito collections and Anopheles philippinensis/nivipes (2.05%) was the most abundant. Japanese encephalitis and dengue vectors constituted 25.3 and 0.05% whereas the known vectors of both Japanese encephalitis and filariasis formed 50.9%. The mean (±SE_mean) of annual parasitic index, slide positivity and Plasmodium falciparum percentage among the civilian population during the study period were 1.46 ± 0.37, 1.65 ± 0.77 and 50.2 ± 10.7. The filariasis vector Culex quinquefasciatus was resistant to DDT with 65.4% mortality whereas the DDT resistance in the Japanese encephalitis vector Culex vishnui gr. with 91.9% mortality needs to be confirmed. All other species tested were susceptible to DDT, deltamethrin and permethrin.

Conclusion

Targeted interventions are needed to reduce the disease burden and vector activity in the villages adjoining the military station. The use of insect repellents, bed nets and repellent impregnated uniforms by the troops should be ensured for protection from vector borne diseases.