In an effort to combat global diseases transmitted by mosquitoes, scientists are turning to some pretty novel techniques, one of which includes a new method to store, transport, and deliver thousands of genetically modified mosquitoes to locations around the world.
To understand why they’re doing it, we need to head back 50 years to the southern US. At the time, screwworm parasites were infecting southerners, feeding on their flesh and just generally wreaking havoc. So, researchers created sterile males in the lab and unleashed them in southern communities. The males would still “mate” with females but wouldn’t produce any offspring, eradicating the flies from the region.
But screwworms are much hardier and easier to transport than mosquitoes, not to mention an adult male mosquito won’t travel more than 200 meters (around 650 feet) in a lifetime. The predicament lies in finding a way to successfully move the engineered bugs in a safe way to a precise location. To figure out standard shipping protocols for mosquitos, a team of researchers at New Mexico State University wanted to know how tightly they could pack live mosquitos.
The team used Aedes aegypti, a species of mosquito that is primarily responsible for the vector of yellow fever, Zika, and dengue. To set the standard for shipping mosquitoes, they first needed to determine the optimal storing temperature that results in the highest survival rate, which, after a series of tests, turned out to be 14°C (57.2°CF). They then needed to figure out how compact they could pack up thousands – even millions – of mosquitoes into a small space. Using a simple plastic syringe, they counted out a precise number of the little buggers and put them into a 10-millimeter syringe and induced compression by inserting a plunger to the 1-millimeter mark.
Lab technician Immo Hansen said his team was “astonished how many mosquitoes you can fit into one [syringe], up to 2,500.” Fortunately for us, they captured the entire claustrophobic episode on video.
If you’re thinking it reminds you of your morning commute by train, then you’re not alone. After another series of tests, the team found that the most efficient method to transport the mosquitoes was by placing 240 of them per 1 cubic centimeter – that translates to about 1,200 mosquitoes on one teaspoon.
Next up, they needed to apply their new method by actually shipping the test-tube skeeters. They packed the syringes into Styrofoam packaging, cooled them at the optimum temperature, and shipped them from New Mexico to California. Although many mosquitoes came out with missing scales or damaged wings, the majority showed up in one piece and even held up better than those that weren’t as tightly packed.
"The high mortality of the not-so-densely packed mosquitoes in our real-world shipping assay was unexpected," explained Hansen. "We hypothesize that the vibrations during transport, especially during the flight, affected the loosely packed mosquitoes more than the densely packed ones."
The team plans to test their method in field experiments next. In the meantime, you can find the study published in the Journal of Insect Science.