Malaria, which killed some 450,000 people globally in just 2015, is no small threat—the World Bank forecast last year that its rising incidence would be one of the significant challenges of climate change. The burden of the disease is severest in the poorest regions of the world—sub-Saharan Africa and parts of South East Asia—with the former accounting for almost 90% of deaths due to malaria. With falling efficacy of the array of drugs available—resistance to artemisinin, the newest anti-malarial compound on the block, has been noticed in some parts of South East Asia—and a suitable vaccine candidate yet to be discovered, researchers the world over are experimenting with unconventional solutions to put a curb on the disease. That many of these involve debilitating the vector—mosquitoes—is by no means incidental.
The latest suggested method, reported in Nature, is infecting the female Anopheles mosquito—which carries the dreaded malarial pathogen, Plasmodium—with a bacteria, Wolbachia, that wreaks havoc with the mosquito’s reproduction. From cytoplasmic incompatibility—which ensures that an uninfected female fertilised by an infected male will only produce unviable eggs—to feminisation/sterility in male mosquitoes, the maternally transmitted (passed on from the mother mosquito to its larvae) bacteria has been demonstrated to cause a host of aberrant phenomenon in Anopheles gambiae, the most common Anopheles species in Africa, and Aedes aegypti, the species that carries the dengue virus.
Now, not only do some strains of Wolbachia compete with Plasmodium for nutrients inside the vector’s body, a particular strain has been demonstrated to bring down vector life in Aedes by almost 50%. Pathogens like Plasmodium also need a critical extrinsic incubation period—EIP—during which it morphs in the vector’s body into a form that can infect and survive in a vertebrate host. This depends on temperature, the strain of the pathogen and, ultimately, the lifespan of the vector. If the vector were to die before the EIP ends, Plasmodium transmission comes down as well.
At the same time, biotech companies have been developing other methods to bring down mosquito-borne diseases. UK-based Oxitec has developed a genetic modification that causes Aedes mosquitoes to die in the larval stage. Modifying just two genes in the male Aedes mosquito ensures that the larva from a mating with an unmodified female don’t reach maturity. Taking this outside the lab could potentially cause Aedes populations in the wild to crash—field trials in Brazil showed that local wild-type Aedes population crashed by 90%—thereby bringing down transmission of dreaded pathogens like the dengue and the Zika viruses.
You would think that any solution that kills pesky mosquitoes would be a hit and should already be on the ground. But Oxitec has been thwarted in both Brazil and the US, by regulators. While Brazil’s national biosafety regulator CTNBio cleared the Aedes strain that causes larval mortality, the country’s health regulator Anvisa has virtually killed off the proposal to release the strain in the country following public protests built on unfounded fears—like Oxitec’s mosquitoes, and not the Zika virus, caused microcephaly in infants, though independent tests have testified to the contrary.
Similarly, in Florida Keys in the US, over 155,000 people signed a petition to prevent Oxitec’s mosquitoes from being released there. “More aggressive species, like the Asian Tiger, will move in to fill the void”, “no local cases of dengue in Florida Keys” and even “bringing down Aedes population could destabilise the environment” have been proffered as arguments against GM mosquitoes. Meanwhile, Zika threatens to cross over from Latin America.
More power to renewables
If it was Solar Impulse 2—the long-range, piloted aircraft created by Swiss entrepreneurs—which made headlines last year by beginning a circumnavigation of the globe, it is Solar Voyager, an autonomous, fully solar-powered boat, that is generating all the buzz now by being on course to cross the Atlantic, sailing along at a walking pace.
The 250-kg aluminium “kayak” is fitted with a 240W solar array and a power subsystem that can generate up to 7kWh a day in summers and 3kWh in winters. Most of the power will be used up by the boat’s fouling-resistant propulsion system, while the remainder goes to various electronic controls on the boat.
At the current level of output, Solar Voyager—which was 200 miles due east of the American coast at Boston on Thursday (the boat’s location is available on a real-time basis via a tracking website, thanks to it being propped with multiple satellite-enabled positioning systems)—is expected to reach Portugal sometime in September.
Created by two American engineering enthusiasts, Christopher Sam Soon and Isaac Penny, with very limited resources, the project is as “rudimentary” as it gets. But if it proves successful—and at the moment that looks very likely—it would be the first time that a fully solar-powered boat would have made it across an ocean. Though, as it has been with Solar Impulse 2—whose batteries malfunctioned in the Asia leg of its trip and took months to be fully repaired—concerns abound about the feasibility, given the available apparatus, of substituting conventional energy sources with renewables and the durability of the boat itself. Nevertheless, both the robotics and the renewables community are following the experiment keenly.
As an aside, Solar Voyager is not the first autonomous boat to attempt a voyage across an ocean or even the first to do so banking on a renewable source of energy—Liquid Robotics, a US-based company, did both in 2012 with its Wave Gliders that crossed the Atlantic, drawing electrical power from the waves of the ocean itself.
With a Tesla already disrupting the automobile industry with battery-powered and autonomous cars, it isn’t very far off in the future that air and sea transport will be similarly disrupted. Countries are already committing to cut fossil-fuel consumption in the face of the mounting challenges from climate change, and there is a race to harvest and distribute commercially-renewable substitutes. These would also need new thinking on machines that can use them.
A Solar Voyager, a Wave Glider or an Infinium (the University of Michigan’s solar-powered car) are just prototypes today, but they could very soon evolve into marketable products.