the first approach, the scientists fed mosquitoes with a modified bacterium
called Serratia AS1 in a sugar meal
. The bacterium was
modified to produce five anti-Plasmodium effector proteins, which inhibit the
development of the falciparum malaria parasite in the gut. Thus, in this
approach, there were no direct changes introduced in the genetic constitution
of the mosquito. The scientists found that:
‘New genetic approaches to prevent malaria transmission in endemic regions could reduce the need of current preventive measures like insecticides and bed nets.’
the second study, the mosquitoes were genetically modified to increase their
immunity and make them more resistant to infection with the malarial parasite
- The modified bacterium remained in the gut and
inhibited the development of the malaria parasite in the digestive tract. When the scientists integrated it with a gene coding
for a fluorescent protein and fed it to the mosquitoes along with a sugar
meal, they found that it efficiently populated the digestive tract and its
numbers increased more than 200 times 24 hours after the mosquito had a
- The bacterium colonized the accessory glands of the
male mosquito and was easily transmitted sexually from the male to the
female mosquito. When the
infected males were allowed to mate with virgin female mosquitoes, the
fluorescent-tagged bacteria were transmitted to the females and were found
in their gut and ovaries.
- Since the bacterium colonized the ovaries, it spread
easily through generations. The
number of infected mosquitoes increased from 5% to 100% in a single
generation. The infection was maintained in the subsequent generations
that were studied.
- The bacterium did
not affect the life span, blood-feeding behavior or fertility of the
scientists found that:
new approaches ensure that the mosquitoes that have undergone the changes show
resistance to the bacteria, and in addition, the resistance persists and
spreads to subsequent generations
- The genetically-modified mosquitoes showed a preference
to mate with non-modified mosquitoes of the opposite sex. The modified males preferred normal females, while
the normal males preferred modified females. When equal numbers of
modified and non-modified mosquitoes were kept together, around 90% of the
mosquitoes were genetically modified in the first generation and the
number as well as the resistance to the malarial parasite was maintained
through 10 generations.
- The change in the immune status changed the type of
bacteria in the gut of the mosquitoes, which was responsible for the
change in their sexual preferences.
Killing the bacteria using antibiotics temporarily eliminated the preference,
which proved that the altered bacterial status determined the sexual
- The modification
of the mosquitoes did not affect their longevity, the number of eggs laid
or the sex ratio in the offspring. The resistance to the malarial
parasitic infection due to the modification lasted for several
. Further development of these approaches
could reduce dependence on current preventive measures like insecticides.
common tropical disease caused by the Plasmodium parasite and spread through
the bite of the female Anopheles mosquito. Though antimalarial medications are
available, the parasite sometimes develops resistance, which makes it difficult
to treat. Falciparum malaria can take a life-threatening course, while vivax
malaria is characterized by relapses if not treated adequately. Prevention of
mosquito bites using repellents and mosquito nets, and preventing the breeding
of mosquitoes are measures that can control the infection to some extent.
Unfortunately, even mosquitoes are developing resistance to insecticides, which
requires the urgent development of alternative methods.
- Wang S et al. Driving mosquito refractoriness to the malaria parasite with engineered symbiotic bacteria.
- Pike A et al. Changes in the microbiota cause genetically modified Anopheles to spread in a population.