Integrated Vector Management - Biological and Environmental Control of Disease Vectors - page 180

widespread and ei cient vector is St . polynesiensis ,
a voracious biter of humans (there are few
alternative sources of blood meals in the Pacifi c
islands). Thus, its transmission potential can be
relatively high even where vector densities are
low. Dengue is also transmitted by St .
polynesiensis , St . pseudoscutellaris and possibly
others of the St . scutellaris group.
The immature stages of the St . scutellaris
group are found in various types of temporary
water bodies such as water-fi lled containers
(natural and artifi cial), plant axils and tree
stumps, crab-holes, rock pools and water-
storage cisterns. As the adults do not fl y very far,
source-reduction within a radius of 100-200 m
from houses can be ef ective. To prevent dengue
outbreaks and LF transmission, all water
containers, such as discarded receptacles (e.g.
cans and tyres), in domestic and peri-domestic
areas should be either removed or covered
(Kittayapong et al ., 2008). Due to the
desiccation-resistant nature of Stegomyia eggs,
containers in which Stegomyia mosquitoes lay
their eggs cannot just be emptied as a control
measure. The water containers either need to
be cleaned to kill and remove the eggs
(Phuanukoonnon et al ., 2005) or properly
covered so that the female mosquitoes cannot
lay their eggs in the fi rst place. This method is
more ef ective for control for Stegomyia
mosquitoes than it is for other types of
mosquitoes because Stegomyia prefer man-made
objects such as cement water-storage containers.
Thus, these habitats can be more ef ectively
located, covered and controlled than can the
breeding areas for malaria vectors. To ensure
community compliance, legislation for a weekly
'dry day' when all containers of water must be
emptied has been enforced by municipalities
such as Mumbai, Singapore and Hong Kong,
where LF has been eliminated.
In addition to environmental management,
for sustained disease control, other measures are
required, particularly during the rainy season
where good coverage rates are not always
possible. Biological control tools are well
integrated into dengue IVM strategies
(Rodriguez-Perez et al ., 2012). One factor
favouring biological control against Stegomyia is
that their man-made oviposition sites are more
able to contain biological control agents than

the more natural puddle habitats of malaria
vectors. The most successful biological control
tools used so far have arguably been the
invertebrate copepods (see Howard, Chapter 2,
this volume). Other biological control tools are
Toxorhynchites mosquitoes (see Howard, Chapter
2, this volume), larvivorous fi sh (see Chandra et
al ., Chapter 3, this volume) and microbial
larvicides (see above) (Andrande and Modolo,
1991; Lee et al ., 2005). For IVM, there are eight
dif erent methods of environmental manage-
ment that can be used to control the immature
stages of St . aegypti mosquitoes (WHO, 2009b)
in addition to fi sh, copepods, Toxorhynchites
predatory mosquitoes and plants (Rodriguez-
Perez et al ., 2012). One of the reasons that IVM
programmes have been ef ectively used for long-
term dengue control is because larval control is
relatively easy compared to other vector-borne
diseases. IVM has been carried out in Singapore
since the mid-1970s, in China since the early
1980s (Neng et al ., 1987) and in Taiwan since
the late 1980s (Chen et al ., 1994; Wang et al .,
2000).
Presently, many countries around the world
have operational programmes that utilize IVM
for dengue control. An integrated controlled
fi eld trial, performed in French Polynesia,
examined the ef ect of combined interventions
against Stegomyia and Culex mosquito larvae.
They sealed available breeding sites with
mosquito gauze, treated them with 1%
Temephos, covered the water with a 10-cm thick
layer of polystyrene beads, or introduced Poecillia
reticulata fi sh, and detected a reduction in
mosquito bites (but unfortunately did not
examine for any disease outcomes) (Lardeux et
al ., 2002). In Cuba, routine Stegomyia control
involves chemical control of adult and larval
mosquitoes and physically removing container
habitats all backed up by health education
(Vanlerberghe et al ., 2009). In Thailand
(Phuanukoonnon et al ., 2005) and Brazil (Lima
et al ., 2010), community participation and
health education are deemed to be important
components along with chemical control of
adult mosquitoes. In addition, biological larval
control and physically removing or covering
containers are being used (Phuanukoonnon et
al ., 2005; Lima et al ., 2010). IVM programmes
have been highly successful in Stegomyia control