- Mosquito resistance to chemical insecticides remains the major
cause of failure to effectively control mosquito-borne diseases such as
- Genetically altered fungi capable of producing lethal toxins when
the fungal spore comes in contact with mosquito can kill them, thus acting
as biological pesticides.
engineered fungi made to produce spider and scorpion venom makes them lethal to
disease carrying mosquitoes and could emerge as highly effective biological
pesticides to control mosquitoes in the future, according to a recent study from the
University of Maryland, and colleagues from
Burkina Faso, China and Australia.
Genetically Altered Fungi May Be Superior to Chemical Pesticides
According to the World
Health Organization, resistance to
chemical pesticides is one of the chief causes for inadequate mosquito control
The research team hoped to overcome this by developing a biological pesticide that would be effective
destroying disease transmitting mosquitoes
To this end, the team employed the fungus Metarhizium pingshaensei,
which naturally infects
mosquitoes. The fungus infects Anopheles gambiae and Aedes aegypti mosquitoes.
When the fungal spore comes in contact with the mosquito, the spores germinate
and penetrate into the mosquito, destroying it from
‘Engineered fungal spores are highly effective and lethal against disease carrying mosquitoes but safe for humans and other beneficial insects such as honey bees.’
the unaltered state, a much larger dose of fungal spores is needed to kill the
mosquitoes and the process takes time. Therefore, the fungi were genetically altered to enable them to
produce multiple toxins
such as spider and scorpion toxins, singly, together and in
combination with other toxins and make
them more lethal and effective
to Raymond St. Leger, a Distinguished University Professor in the UMD Department
of Entomology and senior author of the study, "Unlike chemical insecticides that target
only sodium channels, many spider and scorpion toxins hit the nervous system's calcium and potassium ion channels, so insects have no pre-existing resistance
Testing the Genetically
Altered Fungi in Mosquitoes
- The genetically modified fungi were
tested on wild mosquitoes that were caught in Burkina Faso and were
- The altered fungi killed the mosquitoes much faster and more
efficiently than the unmodified strain.
- The most effective strains were those that produced a combination of
spider and scorpion venom, derived from the North African desert
scorpion Androctonus australis and another derived from the Australian
Blue Mountains funnel-web spider Hadronyche versuta.
- The scientists also ensured that the
fungal toxin is not released into
the environment by inserting a genetic switch into the fungus that
turns on toxin production only when the fungus is within the blood of the
- Additionally, the authors have determined and made sure that the
fungal spores do not harm or destroy non-target beneficial insects
such as honey bees by exposing them to spore coated fabric (passive
method) and spraying fluid in which the spores were suspended (active
method); it was observed that the honey bees did not die even after 2
weeks of observation.
- Both these toxins have been approved for insecticidal purpose by
the Environmental Protection Agency.
summarize the potential merits of this fungal agent, several layers of biosecurity
as mentioned above ensure that the
biological pesticide is safe for commercial use and additionally its mechanism of action makes development of
resistance in mosquitoes unlikely
this paper, we report that our most potent fungal strains, engineered to
express multiple toxins, are able to kill mosquitoes with a single spore,"
said Brian Lovett, a graduate student in the UMD Department of Entomology and a
co-author of the paper. "We also report that our transgenic fungi stop
mosquitoes from blood feeding. Together, this means that our fungal strains are capable of preventing transmission of disease by
more than 90 percent of mosquitoes after just five days
." Current and Future Plans of Testing the Biological Pesticide
- The recent findings have
encouraged the authors to perform on-field testing on mosquitoes in
Burkina Faso. Currently they are testing the insecticide within a custom
made enclosure made of netting.
- Also, they are testing the insecticide on
insect species related to mosquitoes such as midgets and gnats to
determine whether non-target insects are affected or not.
- Finally, the team plans to release
the spores in the open on wild mosquito populations.
"This is our first in-depth study of
the effects toxin-expressing fungi have on mosquitoes, beyond their ability to
kill faster. This is also our broadest characterization of our arsenal of insect-killing
spider and scorpion toxins," Lovett said. "Our results directly
extend our understanding of how these technologies may be used in the field
against mosquito pests."
- Etienne Bilgo, Brian Lovett, Weiguo Fang, Niraj Bende, Glenn F. King, Abdoulaye Diabate, Raymond J. St. Leger. Improved efficacy of an arthropod toxin expressing fungus against insecticide-resistant malaria-vector mosquitoes. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-03399-0