Biology Reference
In-Depth Information
driven environmental cleaning, St . aegypti
numbers were reduced by 87-99% when
compared to the control village. Finally, St .
aegypti larvae disappeared from the treated
village (but not the control village), proving that
the use of Mesocyclops as the primary control
agent had managed to eradicate the local
Stegomyia population (Nam et al ., 1998).
Following on from this success, activities
were expanded into 11,675 households in six
communes in northern Vietnam (Kay et al .,
2002). From the beginning, the focus of the
study was on a sustainable and community-
implemented control strategy. Thus, stable
Mesocyclops resources were established in each
commune so that community health workers
could carry out the treatments (and any
necessary re-treatments) themselves. After 2
years, St . aegypti levels were reduced to 0-0.3%
of baseline estimates and St . albopicta popu-
lations were reduced to 0-14.1% of baseline
levels. In several test communes, Stegomyia
populations were even eradicated. Although
ultimately successful, these results did not come
quickly; the authors concluded that full imple-
mentation of community-based control using
Mesocyclops would take more than 1 year to
become ef ective (Kay et al ., 2002).
Further expansion of the project into
central Vietnam also showed the elimination of
dengue vectors from several study communes. In
addition, by year two of the programme, no
dengue transmission was detectable in the three
treated rural communes, even though dengue
transmission (112.8 cases per 100,000) was still
evident in the control areas (Nam et al ., 2005).
The programme was then expanded country-
wide in Vietnam. A 2005 report outlining the
strategy for the ef ective use of Mesocyclops to
control dengue vectors states that St . aegypti had
been eradicated from 32 of the 37 communes,
covering a human population of 309,730 (Kay
and Nam, 2005). Crucially, dengue transmission
has not been reported in the treated areas for 3
years up to date of the published report,
protecting an estimated 400,000 people by using
Mesocyclops copepods as the major Stegomyia
control tool (Kay and Nam, 2005).
Copepods have been successfully used to
control Stegomyia mosquitoes in a range of man-
made water containers throughout the world,
not just in Vietnam. A fi eld trial in Mexico tested
Mesocyclops in tyres, cemetery fl ower vases and
water tanks to control St . aegypti . Three months
after the start of the intervention, cemetery
vases showed a 67.5% reduction in mosquito
larvae (Gorrochotegui-Escalante et al ., 1998). A
successful fi eld trial has also been carried out in
Argentina where Mesocyclops were able to
control St . aegypti populations over the 22 week
study period (Marti et al ., 2004). Similarly, St .
albopicta populations have been reduced by
various cyclopoid copepods in Japan (Dieng et
al ., 2002) and Mesocyclops have also been
integrated into a highly successful integrated
vector management (IVM) programme in
Thailand (Kittayapong et al ., 2008).
Community acceptance is very important
for disease vector control. When communities
are involved in vector control programmes, not
only does it lead to more ef ective mosquito
control (Valerberghe et al ., 2009), but it is also
crucial for sustainability (Wang et al ., 2000).
Copepod use is well received by communities,
and therefore is proving highly sustainable.
Before wide scale Mesocyclops use, 96.4% of
Vietnamese villagers would accept the use of
copepods in their water storage containers to
control dengue vector mosquitoes (Kay et al .,
2002). Copepods were approved by the com-
munity members after implementation and were
still being used 7 years after oi cial involvement
ended (Kay et al ., 2010).
Stegomyia females have been shown to be
attracted to Mesocyclops -infested water to oviposit,
further improving the potential of sustainable
copepod use. In both laboratory and fi eld tests, St .
aegypti females laid signifi cantly more eggs in
water that contained or had previously held
copepods when compared to control water
without copepods (Torres-Estrada et al ., 2001).
This attraction augments the 'egg trap ef ect', i.e.
when more ef ective vector control is achieved
by using copepods rather than by removing
aquatic habitats. Mosquitoes that emerge from
untreated habitats may lay their eggs in
containers containing copepods, resulting in
predation (Marten and Reid, 2007). If copepods
were not used, then mosquitoes would always
fi nd aquatic habitats to lay eggs and Stegomyia
population reduction could be slower.
Despite all the successes, there is a
cautionary note in the deployment of Mesocyclops
for mosquito control. It is not advisable to use
 
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