Study shows efficacy of method for reducing dengue fever incidence

Photo of an Aedes aegypti mosquitoes
Kmaluhia/Creative Commons
Researchers had previously observed that Wolbachia-treated mosquitoes are not able to transfer dengue to humans, but the study was the first randomized controlled trial to test whether introducing the bacteria into a mosquito population could be used as a large-scale public health intervention. (Photo by Kmaluhia under CC BY-SA 4.0.)

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Preliminary data from a study involving UC Berkeley researchers suggests that the “Wolbachia method” could be used to significantly reduce the incidence of dengue fever, a mosquito-borne disease, in populations where the illness is endemic.

Researchers across the globe, including campus School of Public Health professor Nicholas Jewell and postdoctoral researcher Suzanne Dufault, tested this method in a 27-month trial in Yogyakarta, Indonesia and published the study’s initial findings Wednesday. They found that using the Wolbachia method reduced the occurrence of dengue in the treated population by 77%, according to Jewell.

This method involves introducing Wolbachia, a type of bacteria, into populations of Aedes aegypti, the mosquito species responsible for spreading dengue, according to Dufault.

Researchers had previously observed that Wolbachia-treated mosquitoes are not able to transfer dengue, as well as other mosquito-borne diseases such as Zika and yellow fever, to humans, but this was the first randomized controlled trial to test whether introducing the bacteria into a mosquito population could be used as a large-scale public health intervention, according to Jewell.

“We’ve introduced a self-sustaining, pretty low-cost method of controlling one of the most significant infectious disease challenges, especially in terms of vector-borne diseases,” Dufault said.

There are currently no other public health interventions available to treat populations with high incidences of dengue fever, according to Jewell.

To test the method, the team introduced mosquitoes with Wolbachia into half of the city of Yogyakarta, while the other half did not receive the intervention, according to Jewell. The team looked specifically at the incidence of dengue in individuals ages 3-45.

Once the Wolbachia is introduced into the mosquito populations, it is passed down to future generations, Jewell said.

Normally dengue is spread when a mosquito bites a human infected with the disease, and when it bites an uninfected human the mosquito gives that person dengue. In mosquitoes with Wolbachia, however, the virus does not reach their saliva, so the next person they bite does not become infected, according to Jewell.

Although the team initially intended for the study to last three years, Jewell said they had to stop recruiting new patients a few months early because of coronavirus-related complications.

Now that the team has found that the technique works, they plan to introduce Wolbachia-treated mosquitoes into the regions of Yogyakarta that did not receive the intervention in hopes of eliminating dengue from the population, according to Jewell.

“The idea is to roll this intervention out at scale, not only in other parts of Indonesia but in other countries around the world where there’s serious dengue incidence every year and significant morbidity and mortality,” Jewell said.

The trial was conducted by the World Mosquito Program in collaboration with Gadjah Mada University and the Tahija Foundation.

The team will submit a paper with more in-depth data analysis to a medical journal for publication and present its findings to the American Society of Tropical Medicine and Hygiene in November.

Another global team including campus researchers published a study Thursday showing that prior infection with the Zika virus leads to increased risk of having more severe symptoms from a dengue infection.

The findings were based on a population of children who experienced a Zika epidemic in 2016, followed by a dengue epidemic three years later in Nicaragua.

This could make it more difficult to develop a vaccine specifically targeting Zika because the antibodies that fight Zika could be interacting with the dengue virus to make dengue more dangerous, according to the study.

The researchers remain confident, however, that there is still a way to develop a safe vaccine, according to a UC Berkeley news article.

Contact Emma Rooholfada at [email protected] and follow her on Twitter at @erooholfada_dc.