Biology Reference
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dietary ei ciency in inter-specifi c and intra-
specifi c competitions can also be studied in the
laboratory. The functional response analysis and
the determination of attack rate and handling
time are the necessary parameters that will
establish their predatory potential against par-
ticular vector species. It is generally recom-
mended to choose a small number of native fi sh
species with high consumption potential to
study the impact of promising vector control
operations.
Following laboratory bioassays, it is neces-
sary to fi nd out about the ei ciency of
larvivorous fi sh under fi eld conditions. Generally,
the comparison of per-dip density of mosquito
immatures recorded before and after the
introduction of larvivorous fi sh in mosquito
breeding habitats provides a good parameter to
establish the predatory capacity of a larvivorous
fi sh. However, a detailed study on the biodiversity
profi le and the number of benefi cial species is
necessary to know if there is any negative impact
of the fi sh species in the specifi c aquatic
ecosystem. Several factors contribute to prey
selection in the fi sh according to inter- and intra-
specifi c competition (Hynes, 1961), energy
expenditure (Nilsson, 1978), resource utilization
(Sheldon, 1969), mouth gape (Hyatt, 1979) and
other ecological, behavioural and morphological
traits (Talwar and Jhingran, 1992; Khanna and
Singh, 2003). The gut analysis of fi sh, besides
qualifying them as 'generalist' predators,
provides the basis of higher adaptability in
diverse ecological conditions. This is an essential
criterion to favour their augmentative release in
mosquito larval habitats. In recent years, the
observations on the gut contents of indigenous
larvivorous fi sh of Argentina have provided
evidence in this regard (Marti et al ., 2006). In
addition, prey-predator cycles may also be
af ected by many other factors. For example, the
use of pesticides and fertilizers adversely af ects
both prey species (mosquito larvae) and
predators (fi sh) in agricultural fi elds (Chandra et
al ., 1987; Lacey and Lacey, 1990; Banerjee and
Chandra, 2004) and presence of dense aquatic
weeds may interfere with larval feeding by the
predator fi sh. In wetlands and larger mosquito
larval habitats, predators of mosquito larvae
such as odonate nymphs (Chatterjee et al ., 1997;
Stav et al ., 1999, 2005; Mandal et al ., 2008),
bugs (Saha et al ., 2007) and dytiscid beetles (von
Kögel, 1987; Aditya and Saha, 2006; Chandra
et al ., 2008b) co-occur with the fi sh. These
arthropod predators impart great ef ect on the
mosquito larval community through predation
(see Howard, Chapter 2, this volume). However,
in many instances, the fi sh prey upon the smaller
instars of these insects (Patra, 1993;
DattaMunshi and Choudhary, 1996). Thus, in
wetland and other situations, where these
insects and fi sh co-exist, the trophic cascades
might be complex, since the abundance of the
mosquito larvae and insects will depend on the
interactions with the fi sh population.
Building of skills is essential among
personnel who will handle operations. Thus,
training of local communities and raising
awareness of the public health problems
associated with mosquitoes with community-
based health education should be carried out.
All members of the community should also be
introduced to the use of larvivorous fi sh in
mosquito control, which would prevent them
from fi shing and consumption of the introduced
fi sh (Ghosh et al ., 2006b).
Finally, to assess the overall ef ectiveness of
intervention programmes in mosquito and
disease control, the density of mosquitoes in the
area and overall disease burden of a given area
would be compared before and after
establishment of larvivorous fi sh after a time
span of between 5 and 15 years.
3.6 Conclusions
Strategies for reducing transmission of vector-
borne diseases include host therapeutics, such
as immunization programmes, reduction of
parasite loads in humans via chemotherapy,
and vector control, including modifi cation of
cultural practices through public health
education, environmental monitoring, habitat
modifi cations and chemical and biological
methods.
However, many of these approaches are
inapplicable and unfeasible in underdeveloped
countries, where the vast majority of the
infections occur, due to fi nancial burdens. For
example, cost precludes chemotherapy as a
disease control strategy in endemic regions
where rapid re-infections require repeated
treatment over long periods of time. Moreover,
 
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