|
The Mosquito
Paradox
来自蚊子的矛盾现象
By Martin Enserink
Martin Enserink发表
It seems like common sense: Reduce insect populations, and insect-borne diseases will decline as well. But a new study of dengue, a viral disease transmitted by Aedes mosquitoes, suggests the opposite. Controlling mosquitoes may result in more cases of dengue hemorrhagic fever (DHF), a rare and sometimes fatal disease caused by the virus.
大众看法认为：减少昆虫的数量，昆虫引起的传染病发病率也会下降。但是一项登革热的新研究发现，一种由伊蚊传播的病毒性疾病恰恰相反。控制蚊子数量会引发罕见并且有时致命的病毒性登革出血热（DHF）疾病增加。
Researchers think that tens of millions of people in the tropics become infected with the dengue virus each year. The pathogen can spur dengue fever, which is marked by agonizing muscle and joint pains but is rarely fatal. Some patients, however, develop the more severe DHF, which can cause bleeding and is deadlier. There are still many questions around the epidemiology of both diseases--including the importance of mosquito abundance.
研究者认为，每年生活在热带的人每数百万中就有数十人感染登革热病毒。病原体刺激机体引起登革热，典型症状为肌肉剧痛和关节痛，但是极少致死。但是某些病人症状会加剧发展到DHF，而这会引发出血甚至导致死亡。在流行病学领域中关于这两种疾病仍有许多未解的难题——包括蚊子数量的重要性。
An international team gleaned data from a massive national survey of Aedes mosquitoes performed between 2002 and 2004 in Thailand, where dengue is rife. The researchers compared this information with data on DHF incidence collected by the Thai Ministry of Health. Overall, 83 out of every 100,000 Thai contracted dengue every year. As expected, the team found that DHF incidence went up with the percentage of households per district containing Aedes larvae or pupae (the House Index). But the trend held only to a point. When the House Index climbed beyond 30, DHF incidence gradually declined, the team reports this week in PLoS Neglected Tropical Diseases.
2002到2004年间，一国际小组在登革热流行的泰国统计了大量该国的伊蚊调查数据。研究人员将该数据与泰国卫生部统计的DHF发病率进行了比对。每年10万人中总共有83人感染了登革热。每个区域内，包括伊蚊或其蛹的生存指标每上升一个百分点，则DHF发病率也会随之升高。但是这种趋势只归纳了一点。该小组报告了本周在PLoS被忽视的热带疾病现象：当统计的生存指数上升超过30时，DHF发病率逐渐下降。
Co-author Yoshiro Nagao of Osaka University Graduate School of Medicine in Japan says the probable explanation--which was supported by computer models--is that DHF usually develops the second time a person is infected. When there are lots of mosquitoes, the second infection is more likely to come shortly after the first one, so there's a better chance that the person still has a strong immune response. When mosquitoes are less abundant, more time passes between infections, antibodies decline, and protection wanes.
报告的合著者，毕业于医学校的大阪大学的Yoshiro Nagao称，可能的解释是——计算机模型显示，通常在人体2次感染时引发DHF。当有大量蚊子存在时，2次感染比1次感染时间要短很多，而此时人体的免疫反应依然很强，这就是一有利的信号。而当蚊子数量减少时，交叉感染的时间久，抗体减少，免疫力减弱。
The data show that mosquito control can have unintended consequences, says Nagao. For instance, lowering the House Index to 30 across Thailand might lead to a 40% increase in DHF. In an unpublished study, Nagao and others plan to show that the only way out of the problem is a vaccine, several of which are now in clinical trials.
Nagao称，数据显示控制蚊子会产生非刻意的结果。比方说，全泰国的蚊子生存指数减少到30会导致DHF的发病率增加40%。Nagao及其他研究者筹划显示唯一的解决方法就是现正进行临床试验的几种疫苗。
But dengue researcher Duane Gubler of the University of Hawaii, Honolulu, says the story is more complicated. For one thing, the study's models assume that all dengue strains and mosquito populations are similar. In reality, there's "tremendous variation" between virus strains' infectivity and potential to spread, he says, and some mosquito populations are much better vectors than others. Moreover, the House Index, which gauges mosquito breeding sites, may not be a good indicator of the population's exposure to a virus, says entomologist Paul Reiter of the Pasteur Institute in Paris. What's important is not the number of sites but the number of adult mosquitoes they produce, he says.
但是位于檀香山的夏威夷大学的登革热研究者Duane Gubler称此研究远没这么简单。其一，研究的模型假设所有的登革热损伤和蚊子数量都是类似的。但他称事实上，病毒性损伤的传染性及传播的潜力是复杂多样的，并且某些种类的蚊子比其它容易带菌得多。此外，巴黎的巴斯德研究所的昆虫学家Paul Reiter称，计量蚊子生存繁殖的生存指数也并不一定是好的揭示病毒的标志，重要的不是生存地的数量而是成体蚊子的繁殖量。
| 
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2009-10-25 13:53:00
感谢楼主～