A new tool to fight against mosquitoes carrying the promising east disease

A battle is underway against an invasive mosquito behind a recent increase in local dengue propagation in southern California – and officials may have unlocked a powerful tool to help win the day.

Two vectors control districts – Local agencies responsible for controlling the organizations widespread by diseases – have released thousands of sterile male mosquitoes in certain districts, with a district starting in 2023 and the other from the following year.

The idea was to descend the population of mosquitoes because the eggs produced by a female after a game with a sterile male do not hatch. And only female mosquitoes bite, so unleashing males does not lead to the transmission of diseases such as dengue, potentially fatal viral infection.

Until now, data is encouraging.

An agency serving a large part of the County of Los Angeles has found a reduction of almost 82% of its invasive AEDES AEGYPTI Mosquito population in its release area in Sunland-Tujunga last year compared to a control zone.

Another district, covering the southwest corner of the County of San Bernardino, recorded an average drop of 44% in several highly infested places where he triggered sterile men last year, compared to pre-intervention levels.

The number of global invasive mosquitoes has dropped 33% in the district – marking the first time in about eight years that the population has dropped instead of the increase.

“Not only were on the ground and really saw good reductions, but we received much less calls – people calling for complaining,” said Brian Reisinger, community awareness coordinator for Mosquito and Vector Control District.

But challenges remain. The scaling of the intervention at the level necessary to make a breach in the vast region served by the county district of the did not take place during the night and would potentially require that its owners of the house pay up to $ 20 in annual costs on their property tax bill to get there.

Climate change allows Cashier The mosquitoes – and the diseases they distribute – to move to new areas and make gangbusters in places where they are established.

Dengue abroad and the widespread presence of Cashier Mosquitoes at home “create this perfect recipe for local transmission in our region,” said Dr. Aiman ​​Halai, director of the disease unit in Vector-Borne at La County Department of Public Health.

Tiny scourge, great threat

AEDES AEGYPTI The mosquitoes were detected for the first time in California about ten years ago. Originally from Africa, the species can transmit dengue, as well as yellow fever, Zika and Chikungunya.

Another invasive mosquito, Aedes AlbopictusArrived earlier, but its figures have decreased and it is less likely to distribute diseases such as dengue.

Although the striped black and white AEDES AEGYPTI I cannot fly far – about 150 to 200 meters – they manage to move. Low altitude and biting mosquitoes are present in more than a third of the California counties, including the County of Shasta in the far north.

Cashier Mosquitoes like to bite people – often several times in rapid succession. As the insects spread through the state, patios and backgrounds have been transformed in respite into risky territories.

But the reduction in bugs has proven to be difficult. They can lay their eggs in tiny sources of water. And they could put a few in a vegetable tray and others, perhaps, in a drain. Annihilating the invaders is not easy when it can be difficult to locate all the breeding points – or access to every meter where reproduction is endemic.

This is one of the reasons why the release of sterilized men is attractive: they are naturally able to find their own species.

Mosquito mosquito

The release of sterilized male insects to fight against pests is a proven scientific technique that has existed since the 1950s, but using it to control invasive mosquitoes is relatively new. The approach seems to be caught up in southern California.

The West valley district was the pioneer of the release of sterilized male mosquitoes in California. In 2023, the Ontario -based agency deployed a pilot program before extending it the following year. This year, it increases the number of treated sites.

Greater Los Angeles County Vector Control District launched its own pilot effort in 2024 and plans to target the same area this year – with some improvements in technique and insect farming capacity.

From the end of May, a District of the County of Orange will follow suit with the planned liberation of 100,000 to 200,000 sterile male mosquitoes per week at Mission Viejo until November. A district of Coachella Valley plugs into developing its own program, which could leave the next soil.

Vector officials of the counties of Los Angeles and San Bernardino said that the residents asked them when they could bring a lot of zapped males in their neighborhood. But experts say that for large population centers, it’s not that simple.

“I just answered this morning to one of our residents who says,” Why can’t we have this everywhere this year? ” And it is, of course, because Rome was not built in one day, “said Susanne Kluh, Managing Director of Grand Angeles County Vector Control District.

The Kluh district has a budget of almost $ 24 million and is responsible for nearly 6 million residents in 36 cities and areas not formed in a company. West Valley’s budget This exercise is around $ 4 million and the district serves around 650,000 people in six cities and surrounding county areas.

The approaches between the two districts differ, in part because of the scale with which they work.

West Valley targets what he calls hot spots – areas with particularly high mosquito counts. Last year, before Peak Mosquito Season, he released around 1,000 sterile men bihebdomadaries per site. Then, the district pushed it up to 3,000 for certain sites for the peak period, which takes place from August to November. The idea is to exceed wild men from 100 to 1.. The program equipment costs around $ 200,000 and the district hired a full -time staff member to help efforts this year for $ 65,000.

Salomon Birhanie, scientific director of West Valley, said the district did not have the resources to attack large expanses of land, so it uses the resources it has effectively. Focusing on problematic sites has proven to be sufficient to affect the entire service area, he said.

“Many average to small districts are now interested in using our approach,” he said, because there is now evidence that it can be integrated into the reduction programs “without having to hire highly skilled staff or request a greater budget”.

Salomon Birhanie, Scientific Director of the West Valley Mosquito and Vector Control District, considers a container of mosquito larvae in the laboratory in March 2024. The Ontario -based district was the pioneer of the liberation of a sterilized man Cashier Mosquitoes in California.

(Allen J. Schaben / Los Angeles Times)

In its inaugural study last year, the county district launched an average of 30,000 men per week in two Sunland -Tujunga districts between May and October – seeking to surpass wild men from 10 to 1. Kluh plans that this year’s driver will cost around $ 350,000.

In order to bring the program into a larger area in the district, Kluh said that more funding was needed – officials offering up to $ 20 per unifamilial house. This would be added to the $ 18.97 that the district owners are now paying for the services that the agency already provides.

If investigations sent to a sample of owners are favorable to the new accusation, it will go to a vote in the fall, as required by proposal 218, said Kluh.

There are five vector control districts that cover the county. The Greater The County County is the greatest, which extends from San Pedro to Santa Clarita. It covers most of Los Angeles with the exception of coastal regions and does not serve the valleys of San Gabriel or Antelope.

Galvanized by the disease

Last year, California had 18 cases of dengue acquired locally, which means that people were infected with viral disease in their communities, not when traveling.

Fourteen of these cases were in the County of Los Angeles, including at least seven linked to a small epidemic in Baldwin Park, a city east of the cases of Los Angeles also arose in Panorama City, El Monte and the Hollywood Hills.

The previous year, the State confirmed its first cases acquired locally, in Long Beach and Pasadena.

Although most people with dengue have no symptoms, this can cause serious body pain and fever and, in rare cases. His alias, “Breakbone Fever”, gives a dark overview of what he can feel.

More than a third of the dengue cases last year’s county required hospitalization, according to Halai.

The mosquitoes collect the virus after having bitten an infected person, then spread it by biting others.

Hope and hard truths

Experts in mosquitoes control sterilization to be environmentally friendly because it does not imply spraying chemicals and civil servants could potentially use it to target other disease spreaders – such as natives in the region CULEX Mosquito, a carrier of the Western deadly virus.

New technologies continue to get online. In the summer of last year, California Department of Pesticides Regulation approved the use of male mosquitoes infected with a particular strain of a bacteria called Wolbachia. The eggs fertilized by these males do not hatch either.

Despite promising innovations, certain aspects of the scourge challenge local control.

Since his departure in mosquito control in California almost 26 years ago, Kluh said that the insect season has extended as winters have become shorter. At the time, officials went to work at the end of April or early May and ended around the beginning of October. Now, native mosquitoes emerge in March and invasive insects can remain in December.

“If things happen like that now, we could always circulate dengue,” she said.

Last year marked the worst year never recorded for dengue in the world, with more than 13 million cases reported in the Americas and in the Caribbean, according to the Centers for Disease Control.

Many countries still report dengue numbers above average, which means that there are more opportunities for travelers to bring it home.