By Andrea Hargraves 
Mosquitoes infected with bacteria Wolbachia It may be associated with a 97% reduction in infection rates Dengue fever In three cities in the Abura Valley, Colombia, according to the results of a study conducted by the non-profit World Mosquito program, which was released at the end of last October.
Global mosquito researchers are seeking to limit the spread of deadly mosquito-borne diseases, such as dengue, Zika and yellow fever, as millions of these infected insects spread Wolbachia In areas where these diseases are widespread.
Bacteria Wolbachia Significantly reduces the ability of mosquitoes Aedes aegypti – One of the largest vectors of vector-borne diseases in the world. An infected female transmits the bacteria to her offspring, perpetuating the disease Wolbachia In future generations. Natural crossing ensures the persistence of mosquitoes with bacteria and does not require new releases after mosquito populations with bacteria Wolbachia It was created.
After an initial phase of testing in the Colombian city of Belo, in 2015, researchers expanded the release of these infected mosquitoes to Medellin and Itagui. Although similar research has been conducted in other parts of the world, this is the largest research the program has ever undertaken.
In April 2022, scientists concluded that about 80% of all mosquitoes in Belo and Itagui and 60% in Medellin had been contaminated with bacteria through hybridization. To investigate the impact of this change on dengue transmission, the number of cases reported during the release of infected mosquitoes up to July 2022 was assessed.
Real effectiveness
The researchers concluded that introducing infected mosquitoes into local mosquito populations was “associated with a significant reduction” in dengue cases of up to 97% in each city, compared with data recorded ten years before the trial began.
A case-control study was also conducted in Medellin, showing a causal relationship between the arrival of infected mosquitoes and a decrease in dengue cases. According to the researchers, the results showed a 47% reduction in dengue fever cases in the neighborhoods where these mosquitoes were released.
They claim this was the largest sustained release of these insects. The positive results “highlight the operational feasibility and real-world effectiveness of launch in large urban contexts and the potential to replicate the public health benefits in different environmental contexts.”
Although the study conducted in Colombia is the largest ever completed, researchers from the World Mosquito Program are conducting similar experiments in other countries. A study conducted in Yogyakarta, Indonesia, showed a 77% reduction in dengue cases after applying this method. In the BrazilSo far, a 38% decrease has been recorded.
“Once introduced into the local population, the mosquitoes become infected Wolbachia stay there. It is not necessary to release more mosquitoes,” biologist Rafael Maciel de Freitas, from the Oswaldo Cruz Foundation and the Bernhard Nocht Institute for Tropical Medicine, told DW.
However, Freitas cautioned against concerns that this method may not work forever, given the high possibility that the dengue pathogen will find a way to adapt and bypass the bacteria. Wolbachia. “It is possible that the virus will find a way to overcome this effect,” he noted.
“I wouldn’t say that Wolbachia “This is the solution for dengue, but I think we have a better response to the disease through this route,” Freitas said.
Reservations
This all sounds like good news, and maybe it is. But there are some caveats, such as the high cost of implementing GMP methods.
Furthermore, it is not yet clear whether the decline in dengue cases observed in Colombia and elsewhere can be attributed to this method alone. The disease occurs in waves, meaning that cities that have seen many and frequent cases in the past can go years without new outbreaks.
There are also some areas where mosquitoes spread Wolbachia There appears to be no or moderate decline in dengue cases compared to other locations. Scientists still do not know the factors that make some areas more resistant to this method.
The Global Mosquito Program wants to expand its operations in the next decade, having already announced plans to build a factory in Brazil to produce 5 billion mosquitoes infected with the disease. Wolbachia In the year.