Tag Archives: mosquitoes

Living Insecticides: OX5034 Mosquito Obliterates Iteslf

A plan to release over 750 million genetically modified mosquitoes into the Florida Keys in 2021 and 2022 received final approval from local authorities, against the objection of many local residents and a coalition of environmental advocacy groups. The proposal had already won state and federal approval.

Approved by the Environment Protection Agency in May 2020, the pilot project is designed to test if a genetically modified mosquito is a viable alternative to spraying insecticides to control the Aedes aegypti. It’s a species of mosquito that carries several deadly diseases, such as Zika, dengue, chikungunya and yellow fever.  The mosquito, named OX5034, has been altered to produce female offspring that die in the larval stage, well before hatching and growing large enough to bite and spread disease. Only the female mosquito bites for blood, which she needs to mature her eggs. Males feed only on nectar, and are thus not a carrier for disease. The mosquito also won federal approval to be released into Harris County, Texas, beginning in 2021, according to Oxitec, the US-owned, British-based company that developed the genetically modified organism (GMO)…

In 2009 and 2010, local outbreaks of dengue feverleft the Florida Keys Mosquito Control District desperate for new options. Despite an avalanche of effort — from aerial, truck and backpack spraying to the use of mosquito-eating fish — local control efforts to contain the Aedes aegypti with larvicide and pesticide had been largely ineffective.
And costly, too. Even though Aedes aegypti is only 1% of its mosquito population, Florida Keys Mosquito Control typically budgets more than $1 million a year, a full tenth of its total funding, to fighting it…

The new male mosquito, OX5034, is programmed to kill only female mosquitoes, with males surviving for multiple generations and passing along the modified genes to subsequent male offspring….Environmental groups worry that the spread of the genetically modified male genes into the wild population could potentially harm threatened and endangered species of birds, insects and mammals that feed on the mosquitoes.


Excerpt from Sandee LaMotte, 750 million genetically engineered mosquitoes approved for release in Florida Keys, CNN, 

The Global Experiment with Malaria Vaccine Starts in African States

Thirty years in the making, RTS,S, the malaria vaccine, also known by its brand name, Mosquirix, targets Plasmodium falciparum, the most common and most lethal of four malaria parasite species. It is an answer to a dire need. After decades of declining numbers of cases and deaths, the fight against malaria has stalled. Parasites resistant to the most widely used treatment, called artemisinin-based combination therapy, are spreading, while malaria mosquitoes are increasingly resistant to insecticides. And yet the rollout in Malawi and in two other African countries, isn’t quite the breakthrough the field has been waiting for. Mosquirix’s efficacy and durability are mediocre: Four doses offer only 30% protection against severe malaria, for no more than 4 years. Some experts question whether that is worth the cost and effort

The biggest concerns, however, are about the vaccine’s safety. In the largest trial, children who received Mosquirix had a risk of meningitis 10 times higher than those who received a control vaccine. Mosquirix may not have triggered the meningitis cases—there are other possible explanations—but the possible risk worried the global health community so much that, rather than rolling out the vaccine across Africa, the World Health Organization (WHO) has decided to set up a pilot in Malawi, Ghana, and Kenya in which the vaccine will be given to hundreds of thousands of children.

The Malaria parasite  is a challenging target for a vaccine. It has a complex life cycle that begins when an infected female mosquito bites a human and spits Plasmodium cells called sporozoites into the bloodstream. They multiply in the liver, emerge as another cell type named merozoites, invade red blood cells, and continue to multiply. The blood cells burst, causing fever, headache, chills, muscle aches, and often anemia. (They also flood the blood with gametocytes—the parasite’s reproductive cells—ready to be picked up by the next mosquito.) Along the way, the parasite frequently changes its surface proteins. That makes it an elusive target for the immune system, and for a vaccine.

Mosquirix, developed in the 1980s by a team in Belgium at SmithKline-RIT, now part of GlaxoSmithKline (GSK), stimulates an immune response against a protein that occurs only on the sporozoites’ surface. To bolster the response, the research team fused the vaccine protein with a hepatitis B surface protein and added an adjuvant….

A relative outside, Danish anthropologist and vaccine researcher Peter Aaby of the Bandim Health Project in Guinea-Bissau, offered another argument against introduction. After reanalyzing the data from the biggest trial, Aaby discovered that although the vaccinated children had malaria less often, they did not die less often. Among girls, overall mortality was almost doubled, Aaby told his colleagues at the meeting. “This vaccine is killing girls,” he recalls saying. Whereas WHO expects the vaccine to save one life per 200 children vaccinated, Aaby believes one in 200 will die as a result of it; he predicts “a nightmare.”

Aaby and Christine Stabell Benn, a global health professor at the University of Southern Denmark, have an explanation. The married couple has studied routine vaccinations in Africa for decades and believes vaccines can “train” the immune system in ways that don’t affect just the target disease. Vaccines that contain a living, weakened pathogen—such as the vaccines against measles and tuberculosis—strengthen the immune system generally, Aaby and Stabell Benn say, making recipients better able to fight off other infections. But vaccines that contain a killed pathogen or only bits of it weaken the immune system, their theory goes—especially in girls, because their immune systems seem to respond more strongly to vaccines in general.

Excerpts from Jop de Vrieze, A Shot of Hope, Science Magazine, Nov. 29, 2019, at 1063

What 200 Million Irradiated Mosquitoes Can Do

In July 2019, a combination of the nuclear sterile insect technique (SIT) with the incompatible insect technique (IIT) has led to the successful suppression of mosquito populations, a promising step in the control of mosquitoes that carry dengue, the Zika virus and many other devastating diseases. The results of the recent pilot trial in Guangzhou, China, carried out with the support of the IAEA in cooperation with the Food and Agriculture Organization of the United Nations (FAO), were published in Nature on 17 July 2019.

SIT is an environmentally-friendly insect pest control method involving the mass-rearing and sterilization of a target pest using radiation, followed by the systematic area-wide release of sterile males by air over defined areas. The sterile males mate with wild females, resulting in no offspring and a declining pest population over time. IIT involves exposing the mosquitoes to the Wolbachia bacteria. The bacteria partially sterilizes the mosquitoes, which means less radiation is needed for complete sterilization. This in turn better preserves the sterilized males’ competitiveness for mating.

The main obstacle in scaling up the use of SIT against various species of mosquitoes has been overcoming several technical challenges with producing and releasing enough sterile males to overwhelm the wild population. 

For example, the researchers used racks to rear over 500 000 mosquitoes per week that were constructed based on models developed at the Joint FAO/IAEA Division’s laboratories near Vienna, Austria. A specialized irradiator for treating batches of 150 000 mosquito pupae was also developed and validated with close collaboration between the Joint FAO/IAEA Division and the researchers…The results of this pilot trial, using SIT in combination with the IIT, demonstrate the successful near-elimination of field populations of the world’s most invasive mosquito species, Aedes albopictus (Asian tiger mosquito). The two-year trial (2016-2017) covered a 32.5-hectare area on two relatively isolated islands in the Pearl River in Guangzhou. It involved the release of about 200 million irradiated mass-reared adult male mosquitoes exposed to Wolbachia bacteria

Nei Lingding island, China (view from Hong Kong)

Experts in China plan to test the technology in larger urban areas in the near future using sterile male mosquitoes from a mass-rearing facility in Guangzhou, said Zhiyong Xi, Director of Sun Yat-sen University-Michigan State University’s Joint Center of Vector Control for Tropical Diseases and Professor at Michigan State University in the United States

Excerpts from Miklos Gaspar & Jeremy Bouye, Mosquito Population Successfully Suppressed Through Pilot Study Using Nuclear Technique in China, IAEA Press Release, July 18, 2019
 

How Venom from Spiders Kills Malaria Mosquitoes

In the 1980s, the village of Soumousso in Burkina Faso helped launch one of the most powerful weapons against malaria: insecticide-treated bed nets, which had early field trials there and went on to save millions of lives. But as mosquitoes developed resistance to widely used insecticides, the nets lost some of their power. Now, researchers are hoping the village can help make history again by testing a new countermeasure: a genetically modified (GM) fungus that kills malaria-carrying mosquitoes. In tests in a 600-square-meter structure in Soumousso called the MosquitoSphere—built like greenhouse but with mosquito netting instead of glass—the fungus eliminated 99% of the mosquitoes within a month, scientists report in the  magazine Science.

MosquitoSphere, Burkina Faso

The fungus also has clear advantages, however: It spares insects other than mosquitoes, and because it doesn’t survive long in sunlight, it’s unlikely to spread outside the building interiors where it would be applied.  Fungi naturally infect a variety of insects, consuming the host’s tissues in order to reproduce, and they have been used for decades to control a wide variety of crop pests….Researchers have tested dozens of different fungal strains against disease-carrying mosquitoes, but none was effective enough to pass muster. So researchers from the University of Maryland (UMD) in College Park and the Research Institute of Health Sciences & Centre Muraz in Bobo-Dioulasso, Burkina Faso, endowed a strain called M. pingshaense with a gene for a toxin isolated from spider venom that turns on when it contacts hemolymph, the insect version of blood. In the lab, the team showed its creation could kill mosquitoes faster and that just one or two spores could cause a lethal infection. 

Burkina Faso was a promising place for a field test: Unlike many countries in Africa, it has an established system to evaluate and approve the use of GM organisms. It also has one of the highest rates of malaria in the world, and insecticide-resistant mosquitoes are widespread. For those and other reasons, the U.S. National Institutes of Health funded the MosquitoSphere, which is specifically designed to test GM organisms.

Excerpts fromGretchen Vogel  Fungus with a venom gene could be new mosquito killer, Science, May 31, 2019

Eradicate Mosquitoes Forever: Gene Drives

The mosquitoes are being fitted with a piece of dna called a gene drive. Unlike the genes introduced into run-of-the-mill genetically modified organisms, gene drives do not just sit still once inserted into a chromosome. They actively spread themselves, thereby reaching more and more of the population with each generation. If their effect is damaging, they could in principle wipe out whole species.. If gene drives were to condemn to a similar fate the mosquitoes that spread malaria, a second of humankind’s great scourges might be consigned to history.

Gene drives can in principle be used against any creatures which reproduce sexually with short generations and aren’t too rooted to a single spot. The insects that spread leishmaniasis, Chagas disease, dengue fever, chikungunya, trypanosomiasis and Zika could all be potential targets. So could creatures which harm only humankind’s dominion, not people themselves. Biologists at the University of California, San Diego, have developed a gene-drive system for Drosophila suzukii, an Asian fruitfly which, as an invasive species, damages berry and fruit crops in America and Europe. Island Conservation, an international environmental ngo, thinks gene drives could offer a humane and effective way of reversing the damage done by invasive species such as rats and stoats to native ecosystems in New Zealand and Hawaii.

Such critics fear that the laudable aim of vastly reducing deaths from malaria—which the World Health Organisation puts at 445,000 a year, most of them children—will open the door to the use of gene drives for far less clear-cut benefits in ways that will entrench some interests, such as those of industrial farmers, at the expense of others. They also point to possible military applications: gene drives could in principle make creatures that used not to spread disease more dangerous… The ability to remove species by fiat—in effect, to get them to remove themselves—is, like the prospect of making new species from scratch, a power that goes beyond the past ambit of humankind.

Gene drives based on crispr-Cas9 could easily be engineered to target specific bits of the chromosome and insert themselves seamlessly into the gap, thus ensuring that every gamete gets a copy . By 2016, gene drives had been created in yeast, fruitflies and two species of mosquito. In work published in the journal Nature Biotechnology in September, Andrea Crisanti, Mr Burt and colleagues at Imperial showed that one of their gene drives could drive a small, caged population of the mosquito Anopheles gambiae to extinction—the first time a gene drive had shown itself capable of doing this. The next step is to try this in a larger caged population.

There are also worries about how gene drives might be used to create a weapon. …The need to find ways to guard against such attacks is one of the reasons that the Pentagon’s Defence Advanced Research Projects Agency (darpa) gives for its work on gene drives. Renee Wegrzyn, programme manager for darpa’s “Safe Genes” project, says the work is to prevent “technological surprise”, whether in the form of an unintended consequence or nefarious use. One of the academic teams she funds has made progress in developing anti-crispr enzyme systems that one day might be able to inhibit a drive’s operation.

Oversight needs not just to bring together a range of government agencies; it requires co-operation between governments, too. The Cartagena Protocol on Biosafety, which entered into force under the un Convention on Biological Diversity (cbd) in 2003, provides controls on the transfer of genetically modified organisms. But how it applies to gene drives is unclear—and besides, America has never ratified the convention. An attempt to ban gene-drive research through the cbd, which was backed by the etc Group and other ngos, failed at the convention’s biennial meeting in Cancún in 2016…Like the reintroduction of vanished species advocated by the rewilding movement, gene-drive technology will provide new arenas for the fight between those who wish to defend nature and those who wish to tame it.

Excerpts from Gene Drives: Extinction on Demand, Economist, Nov. 10, 2018, at 24