Hurricane Harvey’s devastating floods, which inundated vast tracks of neighborhoods in August and brought with it the chance of toxic leaks has raised concern recently about another environmental risk: the rise in mosquito-borne illnesses such as Zika and West Nile. Southern U.S. locations are still dealing with lingering flooding and in an effort to be proactive, the Federal Environmental Management Agency says it plans to start spraying insecticide over the Houston area. It also has its eye on South Florida, which is already considered a natural breeding area for mosquitoes.
Many aerial sprays contain an organophosphate insecticide, which the Centers for Disease Control says is safe to use in populated areas. While FEMA and Texas Health and Human Services haven’t published what insecticide it will be aerial spraying, organophosphates are often the treatment of choice because of their low toxicity to humans.
But they are a problem for bees and by extension, for honey producers, which Houston’s surrounding countryside does support.
And widespread spraying for mosquitoes isn’t necessarily a simple answer for eradicating diseases like Zika, West Nile and dengue, researchers point out. It doesn’t stop the mosquito from breeding the next year or in the years following and the program costs millions of dollars to maintain (Many parts of Florida have maintained spray regimens for decades, unable to block the returning spread of West Nile and other diseases.)
In recent months, since taking scope of the toll of Zika’s impact on places like South America and West Africa, some innovative scientists have determined that the real answer is targeting the mosquito’s ability to spread the diseases themselves.
Two research teams — one in California and one in Queensland, Australia — have been working on distinct projects using a bacterial called wolbachia to control the mosquito’s ability to transmit contagious diseases like Zika, dengue and West Nile.
Interestingly, both are working from the starting point of controlling the mosquito’s ability to reproduce eggs that can carry disease, but with different targeted results when it comes to the viability of the mosquito species.
Wolbachia is a common bacteria found in the environment, so much so that it’s often found in some species of mosquitoes. But it isn’t common to the aedes aegypti (often called the yellow fever mosquito) and the aedes albopitus, (tiger mosquito), both known to carry diseases like dengue, West Nile and Zika.
What’s attracted researchers’ attention is that mosquitoes harboring the wolbachia bacteria seem to have a lower ability to spread these diseases, “suggesting that that viral transmission was blocked,” wrote one group of researchers in Brazil.
Scientists have known since at least the 1960s that wolbachia may hold the key to stopping viral transmission in mosquitoes that carry disease ever since Dr. Hannes Laven, a German researcher experimented with breeding wolbachia-infected male mosquitoes with females that weren’t carrying the bacteria. But figuring out why the bacteria actually blocked disease transmission has been the key to stopping disease transmission.
The two projects are both using wolbachia to curtail the two species’ potential to spread these diseases, but with different economic and scientific objectives in mind.
In the city of Clovis, located at the northern edge of Fresno, California, researchers are “marrying” the two groups of mosquitoes (wolbachia-infected males and females without evidence of the bacteria) with the intent of eventually wiping out the aedes albopitus hold on the area.
It’s a big job, with an even bigger goal: to find a way to ensure that the mosquito can’t produce the larvae that carries these diseases.
It also carries a big budget because the release of wolbachia-carrying males must be flown in from outside the state twice weekly and released into the wild. The company, MosquitoMate, run by Dr. Stephen Dobson, already has a website up to explain to residents why millions of male non-biting mosquitoes can help control the potential for disease in their area. The company offers to provide an estimate based on the size of the homeowner’s back yard.
MosquitoMate points out that unlike some treatment models, the company doesn’t use genetically modified mosquitoes. That’s been a plus in the eyes of some residents, such as in Florida, where residents on Key Haven turned down the option of hiring UK-based Oxitec to release its “GMO” mosquitoes into the area. Interestingly, the objective is pretty much the same: to nullify the ability of infection-carrying mosquitoes to survive.
On the other side of the world, though, another approach is taking shape, one that has garnered the attention of the Bill and Melinda Gates Foundation, a financial supporter of programs that work toward eliminating the impact of dengue.
Dengue gets relatively less attention in the U.S. than Zika or West Nile, but is considered by the World Health Organization to be one of the fastest-growing mosquito-borne diseases in the world. It has shown a 30-fold global increase in the past half-century, presenting increasing challenges for health care workers and researchers in tropical areas of South America, Africa and the Caribbean — including those areas often most vulnerable to climate change impacts.
The World Mosquito Program (formerly called the Eliminate Dengue project), run with the backing of the foundation for the Institutes of Health, the Bill and Melinda Gates Foundation’s Grand Challenges in Global Health Initiative, the Tahija Foundation in Indonesia and the Australian and New Zealand governments, aims to develop a non-profit model that can curb disease in the aedes aegypti mosquito, and do so without completely wiping out the species. The methods, similar to Dobson’s was developed by a research team run by Dr. Scott O’Neill, at Monash University, Melbourne (Queensland) and has increasing backing from governments across the globe. The program, now taking root in more than 10 countries across the world, isn’t just vital to curbing proliferation of the carrier, it has promise in stopping the spread of some of the world’s most virulent diseases.