Malaria, a deadly disease caused by the transmission of parasites called Plasmodium, via a certain insecticide-resistant species of mosquitos known as Anopheles, has been around since the 1800s. In November of 2018, it was reported that in 2017, 92 percent of 219 million cases worldwide and 93 percent of 435,000 deaths were from Africa.
Indeed, this is an alarming set of records, which is why researchers are trying to engineer some solutions. The fungus species known as Metarhizium pingshaense has already been known to kill malaria-carrying mosquitos since 2011. However, in a recent study conducted in Burkina Faso in Africa, the fungus becomes deadlier to the mosquitos when injected with a toxin from spiders called Hybrid. The fungi have been engineered so that when they come in contact with the mosquitos, they produce the same toxin. "We're just bypassing the spider fangs and getting the fungus to do the same job," says Raymond St. Leger, one of the research authors and an entomologist at the University of Maryland.
Burkina Faso, being a region where malaria is endemic, became the prime location for the study. The researchers, together with some scientists and a few villagers, have built a frame, covered by two layers of mosquito nets and was divided into a few sections with huts inside. A wall on each hut provided a place for the female mosquitos to rest after feeding. It had a black cloth coated with sesame oil, which helped fungal spores stick to the cloth. This became their independent variable-some huts had a cloth with no spores, some with the spores without the toxin, and some with spores that were engineered with the toxin, Hybrid. The huts were populated with 1,000 male and 500 female mosquito larvae that were collected by the locals from puddles. After mating, the female mosquitoes fed on the blood of calves allowed into the huts for three nights each week. The researches then counted the number of surviving adult mosquitoes for each generation.
Results showed that both the engineered and the non-engineered fungi killed about 75% of the mosquitoes over 2 weeks, but the engineered ones killed the mosquitoes at a higher rate, essentially acting as a catalyst.
"The results are exciting, but there's still a lot of work to be done," said Adriana Costero-Saint Denis, entomologist at the U.S. National Institute of Allergy and Infectious Diseases, which provided funds for part of the study. "The researchers still need to work out variables, including where best to hang the cloth-from the ceiling or on walls, in bedrooms or near doors and windows, she says. And while the study was in a contained, artificial environment," she says, "temperature and humidity were natural, so it's better than the lab."
And although these results are as "exciting" as Costero describes, Matthew Thomas of Penn State University says that it is yet to be established whether the research is an improvement to what we already have. "The genetically modified fungus cut the study's mosquito populations to about 25 percent of the starting number in 14 days, while other species of unaltered fungi can kill 100 percent of mosquitoes in five or six days," he says. "So it's not clear what benefit this has provided. It's almost like a technology looking for an application, rather than a problem needing fixing."
