Laboratory-modified mosquitoes reduce dengue fever cases – DW – November 2, 2023

In three cities in Colombian Abura Valley are infections Dengue fever It decreased by 97 percent. This may have something to do with mosquitoes infected with Wolbachia bacteria. This means that mosquitoes themselves cannot transmit dangerous viruses. Researchers from the non-profit organization gave these results Global Mosquito Programme (WMP) at the end of October at the annual meeting of American Society of Tropical Medicine and Hygiene a favour.

The Global Mosquito Program seeks to stop the spread of a number of life-threatening diseases transmitted by vectors such as mosquitoes. It does this by releasing millions of mosquitoes infected with Wolbachia bacteria into places where diseases are widespread, e.g Dengue, Zika and yellow fever It happens often.

How can Wolbachia bacteria prevent dengue fever?

Wolbachia bacteria reduce the ability of the Aedes aegypti mosquito to transmit disease. This type of insect is one of the most common types of insects that spread serious vector-borne diseases.

After a pilot test in 2015 in the Colombian city of Belo, the researchers expanded their activities to the nearby cities of Medellin and Itagua. Although they conducted similar experiments around the world, these versions were the largest they had conducted within this program to date.

In April 2022, researchers found that about 80% of all mosquitoes in Belo and Itagui were infected with Wolbachia mosquitoes through hybridization, and in Medellin the number was about 60%.

Promising results

In order to find out whether this infiltration actually had an impact on the number of dengue fever cases in the three cities, the researchers evaluated the results during the experiment, which lasted until July 2022.

The researchers found that introducing infected mosquitoes into local mosquito populations was associated with a significant reduction in dengue cases. Compared to the ten years before the start of the experiment, they recorded a decrease of up to 97 percent.

They also conducted a case-control study in Medellin. They found a causal relationship between the use of infected mosquitoes and the decline Dengue fever-cases. According to the researchers, dengue cases decreased by 47 percent in neighborhoods where mosquitoes were released.

The positive results “confirm the feasibility and true effectiveness of this deployment in large urban areas. They also demonstrate that the public health benefits are replicable in different environmental settings.”

One application is enough

The launches in Colombia are the largest to date. Researchers from the World Mosquito Program have previously conducted similar experiments around the world. Previous studies have shown that in Yogyakarta, Indonesia, for example, dengue cases decreased by 77 percent as a result of this program. In Brazil, the burden of disease has decreased (so far) by 38 percent.

Several options are currently being studied to successfully control diseases transmitted by vectors such as mosquitoes. According to experts, the method used by the World Mosquito Program is a major advantage. “Once you introduce a Wolbachia mosquito into local mosquito populations, it stays there,” biologist Rafael Maciel de Freitas told DW in April 2023. “You don’t have to release more mosquitoes.” Freitas for Brazilian Oswaldo Cruz Foundationand on Bernhard Nocht Institute of Tropical Medicineemployee.

However, according to Freitas, there are concerns that this method will not work forever. It is very likely that the cause of dengue finds a way to adapt to and then overcome the Wolbachia bacteria. “I can’t say that the Wolbachia method is the solution to dengue, but I think that this way we have a better chance of dealing with the disease,” Freitas said.

It’s a lot to do

This all sounds like good news. However, there are some caveats: First, GMP’s methods are expensive to implement. On the other hand, it is currently unclear whether the decline in dengue cases observed in Colombia and elsewhere can be attributed solely to Wolbachia -infected mosquitoes. Sometimes, a city located in a dengue-prone area may not see an outbreak for years.

In addition, there are certain regions where mosquitoes infected with Wolbachia bacteria do not appear to cause a reduction in dengue cases, or a much smaller decline than in other regions. Researchers are still unsure why mosquitoes in some areas are resistant to this approach.

The World Mosquito Program wants to expand its activities over the next ten years. Earlier this year, plans were announced to build a factory in Brazil that would infect about 5 billion mosquitoes with Wolbachia each year.