Releasing Mosquitoes with Drones, the Hope for Fighting Dengue in America

America fights mosquitoes that transmit dengue fever with fumigations. (EFE)

14ymedio biggerEFE (via 14ymedio), Lucy Lorena Libreros, 27 August 2022 — America continues to fight a hard battle to counteract the advance of dengue fever in the region. In addition to measures such as the elimination of mosquito breeding sites and fumigation, there is now an unusual technique: using drones to release communities of mosquitoes ’vaccinated’ with a bacteria in areas with a high incidence of the disease.

The innovative experiment — whose benefits are recognized by the health authorities on the occasion of the commemoration of International Day against Dengue this Friday — will take place beginning in September in Cali, the third largest city in Colombia, which in 2019 registered 15,000 cases of dengue fever.

This figure represents 15% of the total reported in a country where it’s estimated that more than 25 million people are at risk of contracting the disease. So far this year, the figure has reached 1881.

But how can we understand that it’s the aedes aegypti mosquito itself, the transmitter of dengue, Zika and chikungunya, that is now in charge of curbing these diseases?

Ana María Vélez, a representative of the World Mosquito Program (WMP), makes it look simple: “These transmitting mosquitoes, which are released in a controlled way in areas with a high incidence of dengue, are carriers of a bacterium called wolbachia, which interrupts their ability to transmit diseases to people.”

Starting in September, WMP, in partnership with the Ministry of Health of Cali, will release — for the first time in America — between 150 and 200 adult mosquitoes that carry the bacteria in different parts of the city, through an 8-motor and 2-meter-long drone, which, guided by a GPS, will accurately recognize the areas where these “new” mosquitoes are needed.

Although it will be the first time that drones will be used, this technique of releasing mosquitoes with wolbachia has already been successfully tested in countries such as Brazil — one of the most affected by dengue — where the bacteria have achieved significant reductions in the number of cases.

This is because it “is transmitted from generation to generation by the maternal line. That is, the new generations of mosquitoes will be born with wolbachia, in order to sustain the bacteria over time. Studies show that the bacteria can remain in the same area for up to 50 years,” the expert tells EFE.

In the case of Cali — where cases of dengue are endemic, at a rate of about 100 cases per 100,000 inhabitants — the release with drones constitutes the third phase of an experiment that began in 2019 with other types of mosquito releases.

This strategy so far has impacted about 800,000 people. “With this new phase, 300,000 more people will be impacted, which would represent in total about half the population of Cali,” says Vélez.

The release of mosquitoes with wolbachia becomes a new step in the fight against an epidemic, which, in the Americas, had a record year in terms of cases in 2019, especially affecting Brazil and Central America, with more than 3 million cases and 1,500 deaths.

Although the authorities in the Americas estimate that during the pandemic there was an underreporting of cases of dengue — one of the diseases “that most congests the hospital system,” in the words of Vélez — this year countries such as Brazil, Peru and Mexico have again raised their numbers.

Brazil, with figures up to July of 2022, has had 752 deaths from dengue, which represents an average of 25 per week, according to recent data from the Ministry of Health.

The figure is 205.6% higher than that caused by the disease in 2021, reflecting the resurgence of dengue.

Also, during that period the country recorded 1,288,403 cases of dengue. A number 195.3% higher than for the same period of the previous year, and more than double that recorded in all of 2021 (543,657).

Peruvians were forced to launch an epidemiological alert last April in the face of the sustained increase in cases with high lethality, which — until the twelfth week of the year — had exceeded the highest peaks of notifications recorded in the last four years.

Until then, infections reached 20,491, an incidence rate of 61.35 per 100,000 inhabitants.

In Mexico, the figures have also set off alarms with the authorities. So far in 2022, 3,134 cases have been confirmed, an increase of 78.5% over the same period in 2021, according to figures from the federal Ministry of Health.

To this are added 8 deaths, 3 more than recorded in the same period last year.

Other countries such as the United States are waiting for what happens in the rest of the region. Although three cases of local dengue have been reported in Miami-Dade, the authorities are already taking precautions in the face of the possible appearance of more contagion as a result of immigration.

Central America has been one of the regions most affected by dengue. Honduras, for example, has a total of 14,764 cases of dengue fever and 6 people killed by the disease so far in 2022, according to the Ministry of Health.

Of the total number of cases, 14,485 patients correspond to the classic type, while patients with bleeding or severe symptoms total 279.

On the other hand, Cuba reported 4 times more cases in a week than in the first half of the year. Last Wednesday, the authorities reported the detection in the same week of 11,634 reactive cases of dengue, 3.8 times more than the positive cases reported in the first half of the year (3,036).

The Government also warned about the increase in the breeding grounds for aedes aegypti and, at the beginning of July, revealed that the Island broke the record for the second year in 15 years for the number of breeding points of the mosquito. It described the epidemiological scenario as “complex.”

The figures are of concern not just to countries in the region. The World Health Organization (WHO) estimates that about 390 million dengue infections occur every year in the world, while about one billion people will be exposed to diseases such as dengue fever by the end of the 21st century, as global temperatures increase, according to a study in the specialized journal Plos Neglected Tropical Diseases.

Translated by Regina Anavy


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