A class of drugs found in flea meds for pets could prevent infections in humans
Gene editing and various devices and repellents are also being developed to protect against mosquitoes
Ready to share meds with your dog?
Taking the same well-known flea drugs commonly given to dogs and cats could protect humans against mosquitoes carrying malaria, Zika and other diseases, a new study suggests. They could also protect us from sand flies bearing the tropical disease leishmaniasis.
A class of drugs called isoxazolines, if given to less than a third of the population in areas prone to outbreaks of insect-borne diseases, could prevent up to 97% of all cases of infection, according to research published Monday in the Proceedings of the National Academy of Sciences.
Isoxazolines are contained in the veterinary products fluralaner (Bravecto) and afoxolaner (NexGard), which protect pets from fleas and ticks. An animal’s bloodstream absorbs these medicines, which are given orally, and spreads them throughout the body. The drugs, which remain active for up to three months, kill blood-sucking fleas and ticks.
In humans, a single dose of the medicine might also act as an insecticide effective against mosquitoes and sand flies for between 50 and 90 days, say the collaborating scientists from Calibr, a nonprofit drug discovery institute affiliated with Scripps Research, and TropIQ Health Sciences, an international entrepreneurial enterprise based in the Netherlands. The drugs also were effective against insect strains that are resistant to common insecticides, the researchers say.
The scientists, whose work is funded by the Bill & Melinda Gates Foundation, admit to not testing their theories on actual people but say they’ve conducted experimental studies on mosquitoes and based their calculations on research on Isoxazolines in animals.
Still, give them points for creativity; this is an entirely new strategy for an ancient problem: warding off mosquito- and fly- borne illnesses that sicken millions of people worldwide each year.
A few other unproven and unusual methods for killing mosquitoes are also on the horizon.
Insect zapping fence
Intellectual Ventures, an advanced technology solutions company, has combined software, sensors and lasers to create an elaborate weapon against mosquitoes: the Photonic Fence.
The virtual fence essentially shoots down pests passing within a kill zone that extends as far as 98 feet (30 meters) horizontally and 10 feet (3 meters) vertically. Specifically, it targets mosquitoes, fruit flies and Asian citrus psyllids, an insect that infects and destroys citrus trees.
The photonic fence works by first detecting, through sensors, a passing insect and then measuring its wing beat frequency, shape, size and airspeed in order to avoid confusing a mosquito with, say, a butterfly or a bumblebee. The fence’s internal software system can even discriminate between male and female mosquitoes, since only the females bite humans (and so would need to be destroyed).
Once it decides that a passing insect is a fair target, the fence trains an invisible, infrared laser on it and delivers just enough photonic energy to stop the winged creature midflight. The system, which does not endanger humans or animals, is calibrated to destroy its prey using the least amount of energy possible and so can run on solar power.
Having created its third prototype, Intellectual Ventures believes that the photonic fence is a way to fight malaria and other mosquito-borne health threats while posing an environmentally responsible alternative to the chemical pesticides used in contemporary agriculture.
With the development of the gene editing tool known as CRISPR (or “clustered regularly interspaced short palindromic repeats”), scientists have begun to experiment with mutating targeted genes in disease-causing mosquitoes. Various techniques are being developed, a scientific review indicates.
Just last year, the Florida Keys Mosquito Control District released thousands of male Aedes aegypti mosquitoes carrying a lethal gene on Stock Island in an ongoing field trial. Although only the female Aedes aegypti mosquitoes bite and spread disease to humans, scientists had chosen to genetically modified the males in such a way that they could still mate with the females, yet any resulting larvae would die before maturity.
The hoped-for result in Florida is an eliminated or at least reduced population of female Aedes aegypti mosquitoes and the viruses they spread. (The district has not announced results from this trial run.)
Scientists are also looking at other ways to disrupt the Aedes aegypti mosquito genome, which is about a third the size of the human genome.
One genetic tweak would lead to males carrying a gene that is lethal to females. While females that mate with the genetically modified males would still produce viable eggs, only male offspring would survive into adulthood (and continue to carry an altered genetic code). Every generation, then, would see a dwindling female population until, ultimately, extinction would be reached.
Meanwhile, scientists are also experimenting with the mosquito genome to produce either sterile – or even wingless – breeds.
Although futurists would probably place their chips on genetic interventions, some inventors prefer to revitalize familiar solutions of the past.
Mosquito-repelling citronella torches, along with Tiki lights and cocktail umbrellas, have seen better days. An upgrade to the smelly and smoky backyard mosquito control solution is zone repellent technology such as that created by Thermacell Repellents Inc., an insect control solutions company headquartered in Bedford, Massachusetts.
Thermacell’s spatial repellents can create a 15-foot zone of protection by vaporizing a naturally occurring repellent and dispersing it into the air. The company’s devices rely on the mosquito-preventive abilities of a pyrethroid, an EPA-approved ingredient derived from a naturally occurring compound found in the chrysanthemum flower.
The law of attraction, though counterintuitive, may also aid in the elimination of mosquitoes in small areas. Woodstream Corp., a manufacturer based in Lititz, Pennsylvania, offers the Mosquito Magnet, which operates by releasing a stream of carbon dioxide (CO2), attracting mosquitoes, and then an additional propane-powered technology vacuums the pests into a net. The mosquitoes dehydrate and die, according to the company.
Spatial solutions aside, some scientists prefer combat.
“The enemy of my enemy is my friend.” This familiar adage guides some scientists seeking to decimate the mosquito population in a given habitat or ecosystem. All it takes is the simple introduction of a predator species, such as copepods.
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These tiny crustaceans – less than a couple millimeters long – dine on mosquito larvae in water. University of Florida scientists have focused on two species, Mesocyclops longisetus and Macrocyclops albidus, and found each capable of close to a 90% reduction in larval survival under field conditions.
The researchers believe that more tests and experiments are needed before using copepods for anti-mosquito duty. Still, the tiny warriors are a likely candidate for pest control, since their worldwide distribution means they possess the ability to thrive under a wide variety of field conditions.