An unconventional trick to fight dengue in Indonesia seems to have gone incredibly well.
In a new study published this week, researchers report that cases of dengue, a deadly mosquito disease, dramatically shrunk in areas where they introduced mosquitoes intentionally infected with a bacterium called Wolbachia. The bacteria are intended to prevent mosquitoes from catching dengue in the first place. These results are the strongest evidence yet Wolbachia can help eradicate dengue and other nasty infections spread by mosquitoes.
Over the last few decades, dengue has become one of the most common infections in the world. Also known as bone fever for the debilitating pain it can cause is the viral disease estimated to infect up to 400 million people worldwide and sick 100 million people annually. It can also rarely turn into a life-threatening infection that causes severe internal bleeding, known as bleeding fever.
The duty on dengue has long made it an appealing target for research. In 2016 the first ever dengue vaccine was approved, called Dengvaxia. But the vaccine is only moderately effective and is not recommended for people who have never had dengue before as it may increase the risk of serious illness if the person encounters dengue for the first time after the vaccine (for people who have already had dengue, the vaccine helps prevent subsequent infections serious). So there is still a need for better anti-dengue measures.
In recent years, some researchers have been working on another strategy, the crib from nature itself. Many insects carry often Wolbachia, bacteria that need to live inside cells in order to survive. WolbachiaInteraction with the hosts can be incredibly complex and often symbiotic, to the point where insects rely on them to survive. Some mosquitoes, especially Aedes aegypti, the main vector for dengue, usually does not carry Wolbachia. But when they do, the bacteria make infected male mosquitoes unable to reproduce with uninfected female mosquitoes; at the same time the infection is passed on to offspring. This knowledge has led scientists to create one technique where infected male mosquito eggs are thrown into an area, mature into adults, and then try, without luck that breeding with the local women, which eventually led to the decline of the population.
Other groups have tested a slightly different approach. Their research has shown it when you infect Ae. aegypti mosquitoes with a specific Wolbachia strain, one lifted from fruit flies, they become much less able to catch and transmit dengue. These mosquitoes also spread Wolbachia to the next generation and ensure that the bacteria continue to work as a dengue deterrent without having to go through the long process of trying wipe out the local mosquito population.
Studies of this method have been underway since 2011, including in parts of the United States, led by the United States World mosquito program (WMP). These studies have suggested that the strategy could be successful without causing any adverse effects on humans or wildlife. But the group’s latest study, a three-year-old randomized controlled trial published in New England Journal of Medicine on Wednesday is their biggest test of it yet and it looks to have passed with flying colors.
The study involved about 8,000 residents living in Yogyakarta, Indonesia, where dengue is endemic. Their neighborhoods were divided into 24 clusters, and the team’s infected mosquito eggs were deployed in half of these areas, while the native skeeter population was left alone in the other half. In areas where the infected mosquitoes were planted, cases of confirmed dengue infection decreased by 77% during the study period compared to control districts. Dengue-related hospitalization also decreased by 86% in experimental areas.
“This experimental result shows the significant impact Wolbachia the method may have to reduce dengue in urban populations. This result shows what an exciting breakthrough Wolbachia maybe-a safe, durable and efficient new product class for dengue control is exactly what the global community needs, ”said co-lead author Cameron Simmons of Monash University in a announcement from WMP.
The results of this type of clinical trial, often considered the gold standard in proving that a treatment works, are likely to lead to much greater acceptance of its use. WMP has already promised to address the rest of Yogyakarta and they hope to expand their project to reach areas that cover so many as half a billion people are at risk of dengue within the next decade with approval from governments and residents, Nature News reported last year. In the bestin cases, this technique combined with others could one day lead to the eradication of dengue completely, as well as other mosquito-borne viruses such as Zika and chikungunya.