“We
are projecting to start releasing by March 2020. We have about a million in the
lab. If you go there now, you would witness the mosquitoes going through the
processes. We keep them in cages and feed them on human blood from the Blood
Bank and other blood as well.”
Sherine Huntley Jones,
head of the Vector Control Programme within the Ministry of Health
There
have also been a number of suspected deaths from the illness. Thus the
Government of Jamaica has decided to pull out the equivalent of a Neutron Bomb.
They've
decided to release sterile mosquitoes to halt the reproduction of the female
Aedes aegypti mosquitoes that carries and spreads the disease as reported in
the article “Gov’t
To Release Sterile Mosquitoes To Combat Dengue”, Published Wednesday
February 20, 2019, The Jamaica Gleaner.
The
statistics so far looks grim. As of February 8, there were have been:
1. 1,166
suspected, presumed or confirmed dengue cases since the start of the year
2. 1,023
suspected, presumed or confirmed dengue cases in 2018
So
come 2020, the Government of Jamaica will release 500,000 sterile male
mosquitoes into the environment per week. The idea is that will mate with the
female Aedes aegypti mosquitoes responsible for spreading the deadly dengue
virus and produce stillborn eggs that never hatch.
So
how is this being done?
How male Aedes aegypti
mosquitoes are sterilized
Sterilize
Aedes aegypti mosquitoes is basically making it so that their reproductive
organs cannot fertilize the female mosquitoes.
According
to Sherine Huntley Jones, head of the Vector Control Programme within the
Ministry of Health, there are three (3) ways to sterlize the mosquitoes:
1. Gene
manipulation
2. Irradiation
3. Wolbachia
Bacteria
Jamaica
has chosen the Irradiation, as it is more suited to quick mass production of
500,000 sterile male mosquitoes per week. “Jamaica is using the radiation
methodology. At the National Public Health Laboratory in Kingston, we are into
mass production of mosquitoes. We are now standardising our procedure for mass
growing, with the intention of rearing enough males so we can sterilize and
release them,” said Sherine Huntley Jones, head of the Vector Control Programme
within the Ministry of Health.
This
makes it more like a factory production line where batches of them can be made
and quality control procedures can be performed to makes sure they are all
sterile, as pointed out by Sherine Huntley Jones, quote: “Jamaica is using the
radiation methodology. At the National Public Health Laboratory in Kingston, we
are into mass production of mosquitoes. We are now standardising our procedure
for mass growing, with the intention of rearing enough males so we can
sterilize and release them.”
With
a million already being processed for sterilization, Health Minister Dr
Christopher Tufton is counting on them to do a better job than fogging. Clearly
they cannot keep using the same approach, as it is not working, as pointed out
by Minister Tufton, quote: “We cannot engage the same approach to tackling and
controlling the mosquito population, like fogging and applying chemical to
water. We visited Cayman and looked at their mosquito-control centre. They told
us the mosquitoes used to literally bite cattle till death. Mosquitoes are not
so much of a nuisance [there] anymore”.
So
are there any potential hazards to the environment?
Sterile Mosquitoes and Reproduction - Females
can potentially mutate
Sherine Huntley Jones was speaking with The Gleaner at the Spanish Court Hotel, Valencia, during a seminar titled ‘Mosquito-Borne Diseases: Dengue Fever Impact on the Workforce and Communities’.
The event, put on by the Manpower and Maintenance Services Limited and held in collaboration with the Caribbean Health Management Consultants Ltd and H&L Agro, was fairly well attended.
Good
to note here that it is the females that bite and transmute; males merely
fertilize the females, hence the reason why they are being targeted. “Males do
not transmit disease. Males do not bite. When you hear we are releasing
mosquitoes, do not panic! The females are the ones that bite. They need the
blood to develop eggs. So we will release the males with view of them mating with
wild females to reduce the population,” Jones pointed out.
Albeit
there is no danger as it related to irradiated mosquitoes as pointed out in the
article Scientist Says Nothing To Fear From Release Of Sterile Mosquitoes,
Published Wednesday February 20, 2019, The Jamaica Gleaner.
But
here is the problem.
Mosquitoes and
Parthenogenesis – Mutations possible to adapt to decline in males
The
female Aedes aegypti mosquitoes is not the only mosquito in town; a new breed
is already in the island as pointed out by Minister Tufton, quote: “So what we
do is go out, collect samples, breed them, and dissect them. Through the unit,
we have discovered that there is a new species of mosquito in Jamaica, which we
never knew of before. So we have to apply different methods to control it”.
Albeit
different breeds of mosquitoes cannot interbreed, it might be able to
interbreed with the sterile males and reproduce. This is because for some
insects, they can reproduce asexually, needing only the stimulation of sexual
contact to reproduce i.e. male courtship stimulates them.
This
method of reproduction is called parthogenesis and is common among Greenflies,
stick insects, aphids, water fleas, scorpions, termites and honey bees (Folden,
2018). Albeit it has not been seen in mosquitoes, scientists are yet
explain how other insect and animals evolved to develope this trait.
The
examples listed are all capable of reproducing without males, using
parthenogenesis. In the case of the honey bee, the use of parthenogenesis has
evolutionary benefits, as they elect to use parthenogenesis when the local
population requires more workers, or more queens.
The
possibility exists that millions of years ago, during their evolution, the female
gender of these insects and animals that are capable of parthenogenesis
developed this trait due to a response in a drop in their male sex partners.
Albeit mosquitoes have never faced this problem as honeybees doe, being as they
are not communal creatures, they can potentially evolve this capability due to
deliberate generic mutation if their reproductive system senses a threat to
their continued existence.
Thus,
albeit unlikely, the mosquitoes over time, may evolve a mechanism to basically switch
from sexual to asexual reproduction and thus thwart irradiation and other threats
to their existence.
Being
as they reproduce so fast and the Aedes
aegypti have a live cycle of 1.5 to 3 and produce on average 100 to 200
eggs per batch (Dengue
virus Net, 2019), this evolutionary adjustment may occur rapidly, allowing
them to adapt possible in less than 1000 or iterations or life cycles.
Thus
by 2025, they may be back at it again, this time reproducing via parthenogenesis,
having recovered from the initial shock of their numbers being depleted by irradiation.
Such insects, once they interact with each other, can be induced to fertilize
their eggs without male gamete.
If
the females adapted to irradiation in this way, by 2025 they could continue to
reproduce irregardless, producing females that can self-fertilize via
parthenogenesis and pass on this trait to their young.
References:
1. Dengue
virus Net. (2019). Retrieved from
http://www.denguevirusnet.com/life-cycle-of-aedes-aegypti.html
2. Folden,
S. (2018). ANIMALS THAT DON'T HAVE A MALE FOR REPRODUCTION. Retrieved from
https://animals.mom.me/animals-dont-male-reproduction-9838.html