Hi curiousrao,
When you say ?sterile insect technology?, I think that you mean
?Sterile insect technique (SIT)?. SIT is a biological control
technique whereby sterile males are released into a the environment.
The sterile males mate with fertile females that would have otherwise
mated with fertile males. Males are sterilized using radiation or
chemosterilants. Females that mate with sterile males are unable to
produce viable offspring. SIT is currently being used for agricultural
pests like screw worms and fruit flies.
Although it was used in El Salvador before their civil war, SIT for
mosquitoes is in stages of development. It is being used
experimentally in Africa to control malaria carrying mosquitoes. In
2003, a new facility was opened in Austria by the International Atomic
Energy Agency (IAEA) in order to research SIT for mosquito control.
However, SIT is not being used commercially. See this webpage for an
interview with Bart Knols, and entomologist at the IAEA. He summarizes
his efforts to produce 1 million sterile mosquitoes per day (an effort
with many hurdles to overcome). The $4 million project hopes to be
able to reach its goals in 5 years.
Reuters - Nuke Mosquito, End Malaria?:
http://wired-vig.wired.com/news/print/0,1294,63210,00.html
New IAEA facility - Statement for Inauguration of Sterile Insect
Technique-Malaria Laboratory:
http://www.usun-vienna.usia.co.at/Statements/SIT-Malaria_Laboratory.html
Scientific article (only the abstract is available without a subscription):
Efficiency of techniques for the mass release of sterile male
Anopheles albimanus Wiedemann in El Salvador.:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7406117&dopt=Abstract
In order for SIT to work, billions of sterile mosquitoes need to be
released into the environment over a period of time. One application
of sterile males would not be enough to reduce the natural population
of mosquitoes. Multiple applications to treat newly emerging
mosquitoes would need to be used.
There are many areas of current research with respect to mosquito SIT.
For example methods of release need to be researched, as mosquitoes
are fragile and can be damaged during release. In addition, methods of
reducing the number of females mixed with the sterile males needs to
be researched. As a consequence of breeding large numbers of males,
females inevitably become mixed with the males. Females bite and are
thus able to transmit diseases. A good SIT program should reduce the
number of released females in order to reduce risk of disease. Methods
of sterilization also need to be addressed since current sterilization
techniques harm the male and make them less competitive for females.
One possibility is creating sterile males using transgenics. There is
also the problem of producing enough mosquitoes to release. Consider
the following passage from a university of Florida website.
University of Florida - BIOLOGICAL AND ALTERNATIVE CONTROL:
?Sterile-male release works well in situations where target
populations are low and dispersal is limited, such as screw worm flies
and Mediterranean fruit flies. With mosquitoes, such as Ae.
taeniorhynchus and Ae. vexans, the number of fertile males emerging
from a typical brood is so large that it would be impractical to mass
rear sufficient sterile males to compete with them. Berryman et al.
(1973) indicated that ratios of sterile:fertile males of 40:1 can fail
to reduce populations. Consider the number of sterile males that would
have to be synchronously raised to compete with the single emergence
from a 500 acre salt marsh, where billions of adult Ae. taeniorhynchus
emerge in a 24 hour period.?
http://fmel.ifas.ufl.edu/whitep/ch7.htm
The feasibility of using SIT may be dependent upon a few factors. It
may be more feasible if the target population is isolated. For
example, if an urban area harbors a mosquito species different than
that in the surrounding countryside. Otherwise, eradication within an
area would only be temporary until the immigration of mosquitoes from
the surrounding area occurred.
Potential Concerns about Genetic Manipulation of Mosquitos:
http://pewagbiotech.org/events/0920/bios/curtis.pdf
In conclusion, it appears as though SIT could be a feasible way of
reducing the numbers of mosquitoes in an area if methods of producing
millions of sterile mosquitoes are researched and developed. It
involves releasing large numbers of sterilized males into the
environment using aircraft or other means. Males can be sterilized
using radiation, chemicals, or trangenics. It may be possible to use
SIT if enough people, including government and scientific people, were
able to see the benefit of using SIT instead of using chemical
insecticides. For the average home dweller, though, SIT may be a bit
beyond his/her scope as sterile males are not yet commercially
available, and North American governments are not yet using the
technique.
>>>
Here is a list of other techniques currently in use.
Invertebrate predators
Mosquito fish (Gambusia) - place in ditches and ponds to eat
mosquito larvae.
Other possible fish species include koi, minnows, fantails
and comets.
Diseases
Parasites
Larvicides
Commercial Bti (Bacillus thuringiensis var. israelensis)
Larvasonic - Uses sound energy to destroy larval air sacks
Adulticides
Space sprays - household aerosol sprays e.g. allethrin, resmethrin
Products containing allethrin, malathion or carbaryl methoprene
Repellents
DEET
Permethrin
Citronella
Mosquito traps
Bug zappers - to be used with caution
Mosquito traps - emits a plume of CO2, sometimes mixed with octonol, to
attract biting insects before sucking them up.
ULV foggers
Pyrethrins or 5% malathion can be fogged outdoors.
Cultural Control
Digging diches and ponds -
Removal of breeding sites - reduce sources of stagnant water -
old tires, birdbaths, avoid over-watering lawn, etc.
Mechanical barriers - close windows, doors, etc.
Vegetation management - reduce amount of weeds and vegetation,
e.g. mow lawns reguarly (adult mosquitos like to rest on
vegetation).
American Mosquito Control Association (AMCA) - Mosquito Information:
http://www.mosquito.org/info.php
Colorado State university, University Cooperative Extension - Mosquito Management:
http://www.ext.colostate.edu/westnile/mosquito_mgt.html#t4
I hope this is what you are looking for. If you have any questions,
please post a clarification request *before* closing/rating my answer
and I'll be happy to reply.
Thank you,
hummer
Google Search Terms Used:
El Salvador sterile male
Mosquito control sterile insect technique
Mosquito control
Mosquito sterile insect technology
Biological control sterile insect technique
Biological control mosquito |
Clarification of Answer by
hummer-ga
on
11 Apr 2005 10:53 PDT
Hi curiousrao,
>>>
1. In the last one year since the news item given what has been done
by International Atomic energy activity in SIT
I found this newsletter from the IAEA. It is the December 2004 issue,
and it is currently issued biannually. I cut and copied the relevant
parts, but you may want to go to the actual document because the
newsletter also included a list of meetings on the topic.
Insect Pest Control Newsletter:
"Sterile Insect Technique for the Control of Anopheles Mosquitoes: In
collaboration with counterparts at the Tropical Medicine Research
Institute (TMRI) and the Ministry of Health, Northern State of Sudan,
research in selected parts of the project area has intensified. In
both Dongola and Merowe, areas for intense surveillance of both larval
and adult populations have been selected and stratification of land
use completed. A grid system is used for randomly selecting blocks
(100 x 100 m) in both areas, and these will be searched for breeding
sites at monthly intervals. (Figs. 8 and 9). Using hand-held computers
connected to a global positioning system (GPS), information on the
locality and type of breeding sites, combined with details of mosquito
breeding (species and density) and both physical and chemical
characteristics of the sites, will be collected. In both field
localities, houses are currently being rented to serve as field
stations, and basic equipment has been provided.
These will greatly facilitate the work in Northern State and provide
an ideal base from which to operate. In Khartoum, mosquito colonies
from both localities are being maintained and used for research
purposes. Initial DDT susceptibility tests have shown 100%
knockdown/kill within 1 hr post-exposure. Further insecticide
susceptibility tests are ongoing."
MOSQUITOES:
"The second half of 2004 has seen a substantial increase in research
activities on Anopheles arabiensis, the target species for development
of mosquito SIT. The development of radiation protocols started in
July and continues
to focus on the selection of an appropriate life-stage and radiation
dose, whilst aiming to safeguard the fitness and competitive ability
of sterilised males. Trials, related to the development of a genetic
sexing strain, have intensified since the arrival of state-of-the-art
equipment in Seibersdorf. Research on blood sources other than human
blood is ongoing and a promising combination of bovid blood and
citrate might signal an important step forward towards the
establishment of mass-rearing procedures.
The Dongola colony of An. arabiensis, established in January 2004, is
expected to replace the much older KGB colony (from Zimbabwe) before
the end of this year, and will then become the sole target species for
research. Field activities in Sudan have reached a stage whereby
larval surveillance strategies in the Dongola and Merowe areas can be
initiated at monthly intervals and training on the use of hand-held
computers and GPS systems has been completed. Two field stations in
each of these localities have been rented by the Sudan Ministry of
Science and Technology and are being refurbished for research
purposes. Two consultants, Ms. Michelle Helinski and Ms. Genevieve
Labbe, have joined the project to focus on radiation biology and
genetic sexing, respectively. Dr. Mark Benedict returned to the Unit
in November to continue working in the project on a part-time basis."
Radiation biology of Anopheles arabiensis:
"Pupae, 20-26 hrs old, were irradiated in batches using the following
doses: 0, 25, 35, 45, 50, 60, 70, 80, and 100 Gy. The effects of
irradiation on pupal emergence, induced male and female sterility, and
longevity and mating capability of the males was recorded. Although
replicates of these experiments are still ongoing, it is clear that
irradiation has no negative effect on the emergence rate of the pupae,
which was similar to that of non-irradiated controls. Sterility was
observed by mating the irradiated males and females to non-irradiated
mosquitoes of the opposite sex. Mass oviposition in the cages
occurred, after which fecundity and the hatching rate was determined.
The egg production of irradiated females is almost completely
inhibited at doses larger than 50 Gy, and of the few eggs that are
laid, almost none will hatch. For the irradiated males, 100 Gy induced
99% sterility, while 50 Gy induced 80% sterility (respectively 10-30%
for two repeats). Irradiation does not influence male longevity, which
was similar to control males. The mating capability of the irradiated
males does appear to be negatively influenced by irradiation to some
extent, although there is substantial variation between different
replicates of the same dose. Considering the variation in sterility
levels and mating capability of the males, at least three replicates
per dose will be completed before a definite dosesterility curve can
be drawn and the impact of pupae irradiation
on mating capability is determined. The same dose range will then be
repeated for the irradiation of the adults. There are indications that
irradiation of adults will have less impact on mosquito fitness, but
this needs to be verified. In addition, competition experiments will
be initiated to test the competitiveness of the irradiated males."
Genetic sexing:
"The molecular laboratory is now fully functional, equipped with a
state of the art microinjection platform and a screening system for
the identification of transformed mosquitoes. Genevieve Labbe, from
the University of Lyon has recently joined the group in support of the
molecular research. Current efforts are concentrated on achieving
germline transformation of Anopheles arabiensis, a critical step
required before testing of conditional sexing systems based on lethal
genes can take place. Female egg laying behaviour has been closely
studied in the laboratory. Conditions have been identified that allow
the collection of eggs throughout the day for microinjection
purposes."
Blood diet:
"Research on blood sources other than human blood is currently under
investigation, in particular, the impact of various anti-coagulants
and different types of blood sources and storage procedures on
mosquito feeding response and fecundity. Equine blood was briefly
tested, but resulted in low feeding response and fecundity. For now,
our attention is focused on bovine blood; the expertise in handling
this blood is widely available within the Entomology Unit as tsetse is
reared on bovine blood. Moreover, bovine blood is more readily
available, both here and in the African partner countries, than equine
or porcine blood. Bovine blood was either defibrinated or stored in
citrate and frozen down. Aliquots of this blood were used to feed
mosquitoes aged 4-5 days. Defibrinated
blood resulted in low feeding response and subsequently a low
fecundity. However, citrated blood seemed to elicit a better response.
More research with citrated blood is underway; in particular ways to
increase the attractiveness of the blood by the addition of ATP."
http://www-pub.iaea.org/MTCD/publications/newsletter.asp?id=41
>>>
2. Transgenic approche and its good bad aspects?
Pros and cons of using transgenics to eradicate mosquitoes.
Transgenics are currently being used in the pink bollworm SIT.
http://www.i-sis.org.uk/bollworm.php
However, a similar protocol for mosquitoes has yet to be developed for
mosquitos. Many studies with respect to transgenic mosquitoes aim to
reduce a mosquito?s ability to be a vector for malaria instead of
producing sterile males.
However, theoretically there are pros and cons to transgenic mosquitoes.
Pros
-Able to create a wide variety of males to be introduced into the
environment (e.g. males may introduce sex suppression in females, kill
females, or simply produce sterile sperm.
-Could facilitate sex separation of mosquitoes during breeding program
Cons
-It is difficult to create mosquitoes that are as competitive as wild males.
-Tightly controlled (APHIS is the agency in charge of issuing permits
for the release of transgenic organisms)
-Complicated methods needed to produce transgenic mosquitoes
-Needs public?s compliance
This book could contain a lot of the information that you are looking for.
Book on mosquito/ malaria control. Chapter 16 and 17 may be of interest
http://library.wur.nl/frontis/malaria/toc.html
APHIS Regulations
http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2004_register&docid=fr23ja04-11.pdf
Interesting scientific article available with a subscription.
The first releases of transgenic mosquitoes: an argument for the
sterile insect technique.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12901936&dopt=Abstract
APPROPRIATE SEX-SEPARATION TECHNOLOGY FOR ANOPHELES MOSQUITOES
http://www.anobase.org/embo_meeting/abstracts/transposons-transgenesis/Benedict.pdf
>>>
3. Are there any recent meeting ( in the last 2 years ) on this topic ?
Recent meetings/conferences.
See the IAEA newsletters. They advertise past and future meetings/
conferences. They also mention that you can obtain literature on past
meetings from them.
I hope this is what you were looking for. Good luck with your skeeters!
hummer
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