Climatic variables and malaria incidence in Dehradun, Uttaranchal, India

BACKGROUND & OBJECTIVES: Mosquito-borne diseases particularly malaria and Japanese encephalitis (JE) are becoming most dreaded health problems in Dehradun district. Keeping in view that the climatic factors particularly temperature and rainfall may alter the distribution of vector species--increasing or decreasing the ranges, depending on weather conditions that are favourable or unfavourable for mosquito breeding, it is aimed to find out the effect of climatic factors on malaria incidence with particular emphasis to capture the essential events as a result of climatic variability. METHODS: Mosquito sampling and identification was done using WHO entomological methods and follow-up of recognised keys and catalogues. Data on malaria incidence and meteorological information were gathered in a collaborative study with the District Malaria Office, and the Forest Research Institute, Dehradun respectively. Pearson's correlation analysis was applied for establishing relationship between climate variables and malaria transmission. RESULTS: Higher positive correlation of association was found between monthly parasite incidence and climatic variables (temperature, rainfall and humidity). However, highest significant correlation was found between rainfall and malaria incidence (r = 0.718, p < 0.0001) when the data were staggered to allow a lag of one-month. INTERPRETATION & CONCLUSION: Climatic variables that predict the presence or absence of malaria are likely to be the best suited for forecasting the distribution of this disease at the edges of its range.     

澜沧江流域健康人群血清乙型脑炎病毒抗体调查

采用血凝抑制试验检测澜沧江上游的维西县、中游的凤庆县和景东县及下游的勐腊县健康人血清乙型脑炎病毒抗体阳性率分别为7.50%（18/240）、20.97%（65/310）、24.46%（57/233）和23.84%（77/323）。表明该地区健康人群中普遍存在流行性乙型脑炎病毒隐性感染。     

云南景东县乙型脑炎流行状况调查

目的调查云南省景东县流行性乙型脑炎的流行现状。方法媒介蚊虫调查采用诱蚊灯通宵捕蚊方法,蚊虫乙脑病毒检测采取RT-PCR方法,健康人群血清乙脑病毒抗体检测采用ELISA。结果共采集到蚊虫4属15种6653只,其中三带喙库蚊和中华按蚊属于当地的优势种群,分别占总捕获蚊数的82.07%和10.46%。RT-PCR检测三带喙库蚊和中华按蚊共16批1310只,各有1株感染乙脑病毒;ELISA检测当地健康人群血清乙脑病毒抗体阳性率为72.96%,不同年龄组人群乙脑病毒抗体水平差异有统计学意义(χ2=51.589,P0.01)。结论云南景东县蚊虫种类较多,三带喙库蚊和中华按蚊有传播乙型脑炎的作用。     

Climate variability and Ross River virus transmission in Townsville Region, Australia, 1985-1996

BACKGROUND: How climate variability affects the transmission of infectious diseases at a regional level remains unclear. We assess the impact of climate variation on the Ross River virus (RRv) transmission in the Townsville region, Queensland, north-east Australia. METHODS: We obtained population-based information on monthly variations in RRv cases, climatic factors, sea level, and population growth between 1985 and 1996. Cross-correlations were computed for a series of associations between climate variables (rainfall, maximum temperature, minimum temperature, relative humidity and high tide) and the monthly incidence of RRv disease over a range of time lags. We assessed the impact of climate variability on RRv transmission using the seasonal auto-regressive integrated moving average (SARIMA) model. RESULTS: There were significant correlations of the monthly incidence of RRv to rainfall, maximum temperature, minimum temperature and relative humidity, all at a lag of 2 months, and high tide in the current month. The results of SARIMA models show that monthly average rainfall (beta = 0.0007, P = 0.01) and high tide (beta = 0.0089, P = 0.04) were significantly associated with RRv transmission and maximum temperature was also marginally significantly associated with monthly incidence of RRv (beta = 0.0412, P = 0.07), although relative humidity did not seem to have played an important role in the Townsville region. CONCLUSIONS: Rainfall, high tide and maximum temperature were likely to be key determinants of RRv transmission in the Townsville region.     

Incidence of Japanese encephalitis,visceral leishmaniasis and malaria before and after the Wenchuan earthquake,in China

The objective of this study was to investigate the incidence of insect-borne diseases from 2005 to 2011, before and after the 2008 Wenchuan earthquake in Longnan City, Gansu Province, China. The data include Japanese encephalitis, Kala-azar and malaria cases from 2005 to 2011 that occurred in Longnan City. We calculated the incidence rates and analyzed the epidemiological characteristics of the diseases before and after the Wenchuan earthquake. During 2005–2011, 212 Japanese encephalitis cases were reported in Longnan City, and the average incidence was 1.11/100,000. Compared with any year from 2005 to 2010 the incidence of Japanese encephalitis in Longnan City in 2011 was not significantly different (P ≥ 0.05). From 2005 to 2011, there were 719 Kala-azar cases in Longnan City, the annual incidence was 3.77/100,000, and the incidence in males was higher than females (P < 0.001). Compared with 2011, there was no significant difference in incidence of Kala-azar in 2009 or 2010 (P ≥ 0.05). There were seven total cases of malaria from 2005 to 2011, and the annual incidence was 0.07/100,000. Wudu District and Wen County were the main endemic areas of insect-borne diseases in Longnan City. The results showed that Japanese encephalitis and Kala-azar were common insect-borne infectious diseases in Longnan City, and that the incidence of insect-borne disease did not increase after the Wenchuan earthquake. It is possible that vector control measures implemented after the earthquake prevented an increase in such diseases.     

2019—2020年哈密市蚊虫种类分布及携带病毒调查

目的　了解新疆维吾尔自治区哈密市蚊虫种类及病毒携带情况,并鉴定该市尖音库蚊所属亚种。方法　分别于2019、2020年7月中旬,在新疆维吾尔自治区哈密市伊州区、伊吾县、巴里坤县采用诱蚊灯法捕捉蚊虫,鉴定所捕获蚊虫种属及尖音库蚊种属。采用逆转录PCR技术检测捕获蚊虫携带黄病毒属、甲病毒属、布尼亚病毒属、流行性乙型脑炎病毒、辽宁病毒、Tahyna病毒、蜱传脑炎病毒及西尼罗病毒情况。结果　在哈密市伊州区、伊吾县、巴里坤县共捕获蚊虫1 496只,分属于3属3种。尖音库蚊为优势蚊种,占所捕获蚊虫总数的65.91%（986只）;其次为里海伊蚊,占30.55%（457只）;阿拉斯加脉毛蚊最少,仅占3.54%（53只）。所捕获尖音库蚊经雄蚊尾器鉴定为尖音库蚊指名亚种。经逆转录PCR法检测,所捕获蚊虫黄病毒属、甲病毒属、布尼亚病毒属、流行性乙型脑炎病毒、辽宁病毒、Tahyna病毒、蜱传脑炎及西尼罗病毒均为阴性。结论　2019—2020年哈密市存在尖音库蚊、里海伊蚊、阿拉斯加脉毛蚊3种蚊虫,以尖音库蚊为优势蚊种;所捕获尖音库蚊均为指名亚种,未发现蚊类携带相关虫媒病毒。     

Immunological evidence of Zika virus transmission in Thailand

Objective: To identify immunological evidence of Zika virus transmission in Thailand. Methods: To undertake a preliminary serosurvey of possible exposure to Zika virus, 21 serum samples from cohort of acute undifferentiated fever patients were examined for immunoreactivity to Zika, Dengue, Japanese encephalitis and Chikungunya envelope antigens by Western blot analysis. Results: Twenty of the 21 serum samples showed immunoreactivity to at least one of the antigens, with seven samples showing immunoreactivity to all antigens. Of particular note, two serum samples showed immunoreactivity only to Zika envelope antigen, with no immunoreactivity to other envelope antigens. Conclusions: This study presents the first evidence of Zika virus transmission in Thailand, although as yet the relationship between transmission and possible cases of Zika fever in Thailand requires further investigation.     

Vector competence of New Zealand mosquitoes for selected arboviruses

New Zealand (NZ) historically has been free of arboviral activity with the exception of Whataroa virus (Togaviridae: Alphavirus), which is established in bird populations and is transmitted by local mosquitoes. This naive situation is threatened by global warming, invasive mosquitoes, and tourism. To determine the threat of selected medically important arboviruses to NZ, vector competence assays were conducted using field collected endemic and introduced mosquito species. Four alphaviruses (Togaviridae): Barmah Forest virus, Chikungunya virus, Ross River virus, and Sindbis virus, and five flaviviruses (Flaviviridae): Dengue virus 2, Japanese encephalitis virus, Murray Valley encephalitis virus, West Nile virus, and Yellow fever virus were evaluated. Results indicate some NZ mosquito species are highly competent vectors of selected arboviruses, particularly alphaviruses, and may pose a threat were one of these arboviruses introduced at a time when the vector was prevalent and the climatic conditions favorable for virus transmission.     

Intense transmission of Japanese encephalitis virus to pigs in a region free of epidemic encephalitis

Epidemic Japanese encephalitis recurs annually in the northern provinces of Thailand, but in the southern provinces cases of human encephalitis are rare. We investigated transmission of Japanese encephalitis virus (JEV) to pigs in southern Thailand. Blood specimens from one hundred young pigs at abattoirs in three southern provinces were tested for JEV hemagglutination inhibiting (HAI) antibodies. Seventy-four percent were positive. Ten seronegative sentinel pigs were placed at five locations in one southern province. Seven of the ten pigs developed JEV HAI and JEV IgM ELISA antibodies within two weeks of placement. JEV was isolated from all seven seroconverting sentinel pigs from blood specimens collected 3 to 11 days after placement. Fifteen light-trap mosquito collections at the five locations all included known JEV vectors, some in large numbers. We conclude that there is intense transmission of JEV to pigs in southern Thailand despite the rare occurrence of human encephalitis in the same region.     

福建省2005-2008年临床乙脑病毒分离株的序列分析

目的分析2005-2008年福建乙脑病毒毒株的部分基因组序列,探索乙脑病毒临床分离株的变异和进化。方法临床标本(血清或脑脊液)接种BHK-21细胞,分离乙脑病毒,从培养液上清提取病毒RNA,RT-PCR扩增病毒基因组片段,并进行克隆、测序以及序列分析。结果共分离到5株乙脑病毒。对病毒C/prM区240bp和全长E基因的序列分析表明,近几年的这些临床分离株基因型仍然全部属于G3型。种系发生分析结果显示,新分离株与2002、2003年分离株存在较大同源性。虽然病毒E基因存在少量氨基酸改变,但总体上这些变异不足以影响病毒的致病性。结论近几年福建省的临床乙脑病毒分离株为G3型,新分离株亲缘关系比较接近2002、2003年毒株。     

我国乙型脑炎病毒优势基因型转换及其风险和对策

乙型脑炎是由乙型脑炎病毒引起的人畜共患病,在自然界中主要是通过蚊虫叮咬进行传播,能够引起人的中枢神经系统损伤和猪的繁殖障碍等疾病,对公共卫生安全造成了严重威胁。 由于乙型脑炎病毒在水禽宿主中的适应性差异,导致了病毒优势基因型由 GⅢ型逐渐向 GⅠ型转变。 乙型脑炎病毒优势基因型的转换和流行范围的扩大给疾病防控带来了新挑战,本文对我国乙型脑炎病毒优势基因型转换及其风险和对策进行了综述。     

广东省乙型脑炎流行特征及其防制策略

目的分析广东省乙型脑炎流行特征,探讨防制策略。方法采用SPSS12.0软件建立数据库,进行描述性流行病学分析和多重线性回归分析。结果1990年以来,广东省于1995年和2003年出现2次乙脑发病的小高峰,其余各年度乙脑报告发病率均较低,疫情比较稳定。疫情主要分布在粤西和粤东地区;发病时间集中在每年5～7月,6月份为发病高峰;乙脑报告病例以1～14岁儿童为主,多为无免疫史和免疫史不详者。多重线性回归分析结果显示稻田种植面积、年平均降雨量与乙脑发病率存在统计学关联。结论广东省乙脑流行呈现明显的周期性、季节性和一定的地域性,1～14岁儿童为乙脑易感人群。接种乙脑疫苗和灭蚊是预防控制乙脑流行的重要措施。     

基于生态位模型的云南省血吸虫病传播风险探测研究

目的基于生态位模型预测云南省血吸虫病传播风险,识别高风险区分布,为制定监测与防控措施提供依据。方法收集2004-2015年云南省18个血吸虫病流行县以村为单位的血吸虫病疫情资料和气候、地理及社会经济等13个环境变量数据,采用BIOCLIM、DOMAIN和MaxEnt等3种生态位模型构建血吸虫病传播风险探测模型,并利用受试者工作特征曲线下面积(AUC)评价模型精度。选择最佳模型分析环境变量的重要性,并预测云南省血吸虫病传播风险分布情况。结果构建的3种生态位模型均能较好地预测云南省血吸虫病传播风险的分布,其中MaxEnt模型的预测准确度最高(AUC为0.96±0.01),其次为DOMAIN模型(AUC为0.93±0.04),再次为BIOCLIM模型(AUC为0.88±0.01),三者间差异有统计学意义(P<0.05)。采用MaxEnt模型分析结果显示,影响血吸虫病分布的最主要环境因子为年平均降水量(贡献值为1.52),其次为国内生产总值和人口密度(贡献值分别为1.06和1.03)。采用MaxEnt模型预测云南省血吸虫病传播风险分布结果显示,传播风险区占云南省面积的3.1%,主要集中在西北部地区,其中低风险区和中风险区占2.7%,高风险区面积占0.4%,主要分布在鹤庆县北部、洱源县东部、大理市中部、巍山彝族自治县东北部和弥渡县北部等地区。结论基于MaxEnt生态位模型预测血吸虫病传播风险分布是可行的。云南省血吸虫病传播风险仍存在,高风险区分布较为集中,需有针对性地开展监测和防控工作。     

Modeling and predicting dengue fever cases in key regions of the Philippines using remote sensing data

Objective: To correlate climatic and environmental factors such as land surface temperature, rainfall, humidity and normalized difference vegetation index with the incidence of dengue to develop prediction models for the Philippines using remote-sensing data.Methods: Timeseries analysis was performed using dengue cases in four regions of the Philippines and monthly climatic variables extracted from Global Satellite Mapping of Precipitation for rainfall, and MODIS for the land surface temperature and normalized difference vegetation index from 2008-2015.Consistent dataset during the period of study was utilized in Autoregressive Integrated Moving Average models to predict dengue incidence in the four regions being studied.Results: The best-fitting models were selected to characterize the relationship between dengue incidence and climate variables.The predicted cases of dengue for January to December 2015 period fitted well with the actual dengue cases of the same timeframe.It also showed significantly good linear regression with a square of correlation of 0.869 5 for the four regions combined.Conclusion: Climatic and environmental variables are positively associated with dengue incidence and suit best as predictor factors using Autoregressive Integrated Moving Average models.This finding could be a meaningful tool in developing an early warning model based on weather forecasts to deliver effective public health prevention and mitigation programs.     

Impact of weather variables on mosquitoes infected with Japanese encephalitis virus in Kurnool district, Andhra Pradesh

ObjectiveTo assess the virus infection in mosquitoes during different seasons and correlated with various climatic factors.MethodsThe field collected vectors were screened for Japanese encephalitis (JE) virus after dessication using ELISA method. Most of the positive pools were recorded from Culex tritaeniorhynchus (Cx. tritaeniorhynchus) and Culex. gelidus (Cx. gelidus) during JE transmission season (winter) and some positive pools were also reported during non JE transmission periods (i.e. summer and rainy seasons).ResultsThe minimum infection rates (MIR) of 1.75 from Cx. tritaeniorhynchus and 0.17 from Cx. gelidus has been reported in the year 2002 at the beginning of the study and the values were found nil at the end of the study (2006) from the study areas of Kurnool district.ConclusionsFrom this study it is noted that MIR of Cx. gelidus and Cx. tritaeniorhynchus were modulated by various meteorological parameters. The mosquito vector abundance increases after the monsoon period (winter) and lowest in dry season (summer). Similarly, MIR fluctuated between seasons with higher MIR recorded after monsoon period and lower in the rest of season. Impact of these metrological parameters in JE virus infected mosquitoes is discussed in this paper.     

重庆三峡库区2012年乙脑病毒分离株基因序列分析

目的 通过分析2012年重庆三峡库区蚊虫中分离乙脑病毒株PrM及E基因序列,揭示毒株的遗传特性。方法 对新分离乙脑病毒的PrM及E基因进行PCR扩增,将扩增产物测序。用分子生物学软件进行核苷酸及氨基酸序列分析,并绘制系统进化树。结果 新分离的8株乙脑病毒株均为基因I型,与我国其他省市的既往分离株进化关系较近;分离株与减毒活疫苗株SA14-14-2相比较,PrM区核苷酸同源性在85.1%～86.7%之间,氨基酸同源性在95.1%～96.3%之间;E基因区核苷酸同源性在87.6%～87.8%之间,氨基酸同源性在96.9%～97.1%之间。所有新分离株与疫苗株在E基因存在14个氨基酸差异位点。结论 2012年8株重庆乙脑分离株为基因I型,在E基因区域与疫苗株相比有部分差异。     

Sylvatic transmission of arboviruses among Bornean orangutans.

Wild populations of nonhuman primates live in regions of sylvatic arbovirus transmission. To assess the status of arbovirus transmission in Bornean forests and the susceptibility of wild orangutans to arboviral infection, blood samples of wild orangutans, semi-captive orangutans, and humans were examined. Samples were tested by plaque reduction neutralization test for antibodies to viruses representing three families (Flaviviridae, Alphaviridae, and Bunyaviridae), including dengue-2, Japanese encephalitis, Zika, Langat, Tembusu, Sindbis, Chikungunya, and Batai viruses. Both wild and semi-captive orangutan groups as well as local human populations showed serologic evidence of arbovirus infection. The presence of neutralizing antibodies among wild orangutans strongly suggests the existence of sylvatic cycles for dengue, Japanese encephalitis, and sindbis viruses in North Borneo. The present study demonstrates that orangutans are susceptible to arboviralinfections in the wild, although the impact of arboviral infections on this endangered ape remain unknown.     

流行性乙型脑炎病毒NS5蛋白的表达

目的 在大肠杆菌中表达并纯化流行性乙型脑炎病毒NS5蛋白,为进一步研究乙脑病毒NS5蛋白的结构与功能奠定基础。方法 根据乙脑病毒NS5蛋白的基础序列,设计两对PCR引物,采用RT-PCR法分别扩增乙脑病毒JaOH0566株部分及全长NS5基因。将扩增产物分别克隆到表达载体pQE30。筛选重组质粒,转化大肠杆菌表达重组蛋白。重组蛋白经金属柱亲和层析纯化。结果与结论 获得了含部分及全长乙脑病毒NS5基因的重组质粒,重组质粒经限制性酶双酶切、DNA序列分析及PCR扩增筛选证实。在大肠杆菌中表现出了带6个组氨酸头的部分及全长的重组乙脑病毒NS5蛋白。经SDS-PAGE及Western-blot分析证实表达蛋白确定是重组乙脑病毒NS5蛋白。