National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai 200025, People's Republic of China.
Parasit Vectors. 2012 Jul 9;5:136. doi: 10.1186/1756-3305-5-136.
Both falciparum and vivax malaria were historically prevalent in China with high incidence. With the control efforts, the annual incidence in the whole country has reduced to 0.0001% except in some areas in the southern borders after 2000. Despite this, the re-emergence or outbreak of malaria was unavoidable in central China during 2005-2007. In order to understand the role of the vector in the transmission of malaria during the outbreak period, the vector capacity of An. sinensis in Huanghuai valley of central China was investigated.
The study was undertaken in two sites, namely Huaiyuan county of Anhui province and Yongcheng county of Henan province. In each county, malaria cases were recorded for recent years, and transmission risk factors for each study village including anti-mosquito facilities and total number of livestock were recorded by visiting each household in the study sites. The specimens of mosquitoes were collected in two villages, and population density and species in each study site were recorded after the identification of different species, and the blood-fed mosquitoes were tested by ring precipitation test. Finally, various indicators were calculated to estimate vector capacity or dynamics, including mosquito biting rate (MBR), human blood index (HBI), and the parous rates (M). Finally, the vector capacity, as an important indicator of malaria transmission to predict the potential recurrence of malaria, was estimated and compared in each study site.About 93.0% of 80 households in Huaiyuan and 89.3% of 192 households in Yongcheng had anti-mosquito facilities. No cattle or pigs were found, only less than 10 sheep were found in each study village. A total of 94 and 107 Anopheles spp. mosquitos were captured in two study sites, respectively, and all of An. sinensis were morphologically identified. It was found that mosquito blood-feeding peak was between 9:00 pm and 12:00 pm. Man biting rate of An. sinensis was 6.0957 and 5.8621 (mosquitoes/people/night) estimated by using half-night human bait trap method and full-capture method, respectively. Human blood indexes (HBI) were 0.6667 (6/9) and 0.6429 (18/28), and man-biting habits were 0.2667 and 0.2572 in two sites, respectively. Therefore, the expectation of infective life and vector capacity of An. sinensis was 0.3649-0.4761 and 0.5502-0.7740, respectively, in Huanhuai valley of central China where the outbreak occurred, which is much higher than that in the previous years without malaria outbreak.
This study suggests that vivax malaria outbreak in Huanhuai valley is highly related to the enhancement in vector capacity of An. sinensis for P. vivax, which is attributed to the local residents' habits and the remarkable drop in the number of large livestock leading to disappearance of traditional biological barriers.
在 2000 年之前，恶性疟原虫和间日疟原虫在我国都很流行，发病率很高。随着防治工作的开展，全国的年发病率已经降低到 0.0001%，除了南部边境的一些地区。尽管如此，2005-2007 年间，中国中部地区仍不可避免地出现了疟疾的再次出现或暴发。为了了解媒介在暴发期间传播疟疾的作用，研究了中国黄淮地区中华按蚊的媒介容量。
该研究在安徽怀远县和河南永城县两个地点进行。在每个县，记录了近年来的疟疾病例，并通过访问研究地点的每个家庭，记录了每个研究村庄的传播风险因素，包括防蚊设施和牲畜总数。在两个村庄收集了蚊子标本，在鉴定不同物种后记录了每个研究点的种群密度和物种，并通过环沉淀试验检测了吸血蚊子。最后，计算了各种指标来估计媒介容量或动态，包括蚊虫叮咬率（MBR）、人血指数（HBI）和产仔率（M）。最后，在每个研究地点估计和比较了媒介容量，作为预测疟疾复发的潜在疟疾传播的一个重要指标。在怀远县的 80 户家庭中，约有 93.0%有防蚊设施，在永城县的 192 户家庭中，约有 89.3%有防蚊设施。每个研究村庄都没有发现牛或猪，只发现了不到 10 只羊。在两个研究地点共捕获了 94 和 107 只按蚊，所有按蚊均经形态学鉴定为中华按蚊。结果发现，蚊子吸血高峰在晚上 9:00 到 12:00 之间。用半夜间人诱捕法和全捕获法估计中华按蚊的人咬率分别为 6.0957 和 5.8621（只/人/夜）。人血指数（HBI）分别为 0.6667（6/9）和 0.6429（18/28），两个地点的人咬习惯分别为 0.2667 和 0.2572。因此，在发生疟疾暴发的中国黄淮地区，中华按蚊的预期感染寿命和媒介容量分别为 0.3649-0.4761 和 0.5502-0.7740，远高于往年无疟疾暴发时的水平。
本研究表明，黄淮流域间日疟原虫暴发与中华按蚊对间日疟原虫的媒介容量增强密切相关，这归因于当地居民的习惯和大型牲畜数量的显著下降，导致传统的生物屏障消失。
