By Sean Zucker –
Think of the greatest threat to mankind and insects rarely come to mind. Big-time killers such as cancer, heart disease and car accidents likely surface and with good reason. But one small pest is not far behind this deadly trio — namely mosquitoes. In fact, the Centers for Disease Control and Prevention (CDC) has called mosquitoes the world’s deadliest animal, accounting for more than 700,000 deaths globally every year. Fortunately, science may now be close to an effective control on this sneaky menace via genetically modified mosquitoes designed to decimate the mosquito population, and limit the serious diseases it spreads.
The CDC confirms that while some mosquitoes are simply a nuisance by leaving mostly harmless bites, others spread harmful and even deadly diseases such as malaria, dengue, West Nile, yellow fever, Zika, chikungunya and lymphatic filariasis. The organization explained that malaria is probably the largest threat, accounting for more than 600,000 deaths across 84 in 2021, the most recent year on record. Additionally, close to 250 million became ill with malaria that year while over 3 billion people around the globe remain at risk of this preventable disease.
While most mosquito-related deaths and illnesses occur outside the U.S. in places such as sub-Saharan Africa and parts of South America and Southeast Asia, as many as 2,500 malaria cases are reported each year in the U.S. Most of these results from people traveling abroad and then returning to the U.S. after getting infected. However, in a frightening development, Johns Hopkins recently reported that for the first time in 20 years, the U.S. has reported home-grown cases of malaria. Admittedly, the number of reports is low to date. But because
malaria transmission in the United States has not been a big issue for decades, surveillance of the disease is relatively low, noted Dr. Photini Sinnis, a professor at the Johns Hopkins Malaria Research Institute.
Zika and West Nile diseases can also climb into the thousands annually in the U.S. although these numbers admittedly fluctuate wildly from year to year, according to Statista.
Malaria and other mosquito-borne diseases are, nonetheless, a growing worldwide problem.
“It shouldn’t be acceptable that children still die of malaria, that expectant mothers still get complications due to malaria,” Jonathan Kayondo, a biologist at the Uganda Virus Research Institute in Entebbe, Central Uganda, explained in Nature.
The institute canvassed Kayondo and other experts on the state of malaria and what tools are being used to combat outbreaks. The unanimous hope was genetically modified mosquitoes. Scientists specifically are targeting the Aedes aegypti strain of mosquitoes due to its female population’s dominance in transmitting these diseases. The aim is to mass-produce male Aedes aegypti eggs in a lab with a genetically altered gene that they will theoretically pass to their offspring after mating in the wild. This modified gene is curated to kill female Aedes aegypti offspring while the male offspring—which do not spread disease—continue to fly around, mating and passing the gene along to others.
The goal may be worthy, but not everyone is convinced the approach will be effective or without troubling side effects. Some of the experts warn this unnatural interference may have consequences for local ecosystems. Others suggest that mosquitos will simply adapt and grow stronger as a result.
“Those who think gene drive is going to be a silver bullet, I think they just haven’t seen how these things have gone,” Kayondo warned. “The mosquitoes and the parasites, they will fight back.”
Trial rollouts have begun despite these concerns. Researchers with the British biotechnology firm Oxitec conducted a practical study with genetically modified mosquitos between 2018 and 2019 and recently released their findings. The team introduced Aedes aegypti mosquitoes into five densely populated areas of Indaiatuba in Brazil during the peak mosquito season.
The initial findings were encouraging. On average, these areas saw an 88 percent drop in the mosquito population during the study. The population decline went as high as 96 percent in some areas.
Admittedly, it is still too early to tell whether mosquitos will adapt to the threat imposed by these genetically modified females. But many see the work as a positive step in the battle against this small but deadly adversary.