50 million cases of dengue infection occur each year
Worldwide, about 50 million cases of dengue infection occur each year, with 22,000 deaths, mostly in children. This includes 100 to 200 cases in the United States, mostly in people who have recently traveled abroad. Many more cases likely go unreported because some healthcare providers do not recognize the disease. In the Western hemisphere, the estimated economic burden of dengue is about $2.1 billion per year.
In a new study, NIAID-funded scientists at the University of California, Riverside, found that reducing levels of a single small RNA, miR-275, in the mosquito Aedes aegypti can stop important metabolic and reproductive functions. A. aegypti mosquitoes transmit the dengue and Chikungunya viruses, so the new findings could have the potential for disrupting the mosquito’s ability to cause human disease. The study was published in December 2010 in the Proceedings of the National Academy of Sciences.
The mosquito’s genome contains thousands of small, noncoding RNA strands, which affect the production of proteins that regulate development, cell growth and reproduction. MicroRNAs, a type of small RNA that is usually 20-25 base pairs long, operate by binding to messenger RNA and disrupting their translation into protein products.
Recently, NIAID Research Scientists at the University of California, Riverside that microRNA plays a critical role in the regulatory vital functions of the mosquito as a vector,” said study author Alexander Raikhel, Ph.D. The functions regulated by miR-275 include blood digestion, fluid excretion and egg development. Although these life cycle steps take place after the mosquito bites a human or animal, disrupting these parts of the mosquito life cycle would reduce disease transmission in the next generation of mosquitoes by reducing survival and reproduction. If the total number of mosquitoes goes down, fewer infected mosquitoes would bite humans, and transmission of disease would also drop.
The importance of miR-275 could be leveraged in disease control efforts. For example, introducing a gene disruptor that reduces levels of miR-275 in the mosquito population could be used to inhibit transmission of dengue and Chikungunya to people. Since the mosquito life cycle lasts only about 6-8 weeks, with just 1-2 weeks in the adult stage, a successful effort to reduce the mosquito population would make a difference quickly.
The researchers are currently working on creating a transgenic mosquito with lower levels of miR-275. Other future directions include studying the gene targets of miR-275 to understand how they interact, and expanding the search to additional microRNAs that affect other stages of the mosquito life cycle.
"Dengue Fever." National Institute of Allergy and Infectious Diseases. U.S. Department of Health and Human Services, 12 May 2016. Web. 28 July 2017.
"Mosquito MicroRNA Essential for Metabolism and Reproduction, NIAID Grantees Find." National Institute of Allergy and Infectious Diseases. U.S. Department of Health and Human Services, 21 Dec. 2011. Web. 28 July 2017.