Biology Reference
In-Depth Information
larvae by larvivorous fi sh is lower than that of
chemical, genetic or environmental control
methodologies; and the application of fi sh is an
ecologically friendly method without having any
signifi cant detrimental ef ects on non-target
populations (Government of India, 2012). In
addition, fi sh live in the same aquatic habitat as
larval mosquitoes and have been able to adapt in
diverse mosquito larval habitats; therefore, there
is no need to create an artifi cial controlling
habitat (Becker
et al
., 2003; Walton, 2007). The
encouragement of the use of mosquito fi sh
G.
ai nis
,
Gambusia holbrooki
and
Gambusia geiseri
of North American origin and the guppies
Poecilia reticulata
of Caribbean origin
as
biological control agents by WHO (1980, 1982,
2003b) has amplifi ed their application in many
countries around the globe (WHO, 2003b).
reduction of 73% in the population of all larval
stages of anopheline mosquitoes. Late instar
larvae of anopheline mosquitoes were reduced
by 87% (
n
= 173), 59% (
n
= 117) and 92% (
n
=
183) due to application of Bti only, fi sh only and
Bti and fi sh, respectively (Imbahale
et al
., 2011).
However, as outlined in a Cochrane Review that
is currently in preparation, the true potential of
larvivorous fi sh as biological control agents can
only be estimated using rigorous fi eld studies
(Burkot
et al
., 2009). Preferably, these studies
should examine disease parameters in addition
to entomological outcomes.
3.3.2 Reduction in disease incidence on
introduction of larvivorous fi sh in larval
habitats in endemic areas
It is important to investigate whether the
reductions observed in larval populations using
larvivorous fi sh (Table 3.1) will also result in
a reduction of overall vector density, and thereby
a reduction in the incidence of diseases. To
date, only a few studies have been conducted
longitudinally under fi eld conditions to
investigate the long term ef ects of larvivorous
fi sh on the incidence of vector-borne diseases.
Below we describe some of the programmes
mainly conducted in India that looked at this
question in some more detail, and discuss
whether any links between the use of fi sh for
larval control and disease incidence can be
drawn.
3.3 Application of Larvivorous Fish
3.3.1 Field trials with larvivorous fi sh
Over a period of more than three decades, many
workers have examined the mosquito larval
feeding potential of a variety of indigenous and
exotic fi shes, individually or in combination, in
the laboratory using larvae of dif erent mosquito
species (Sharma and Ghosh, 1989; Chatterjee
and Chandra, 1996, 1997a,b; Ghosh, A.
et al
.,
2004, 2005, 2006; Hurst
et al
., 2004;
Kusumawathie
et al
., 2006; Bhattacharjee
et al
.,
2009; Gupta and Banerjee, 2009; Matias and
Adrias, 2010; Okorie and Abiodun, 2010;
Anyaele and Obembe, 2011; Haq and Yadav,
2011; Manna
et al
., 2011; Phukon and Biswas,
2011; Ravindran
et al
., 2012). In addition, an
abundance of fi eld studies have been performed,
using fi sh identifi ed as having high larval feeding
rates in laboratory studies, and many species
signifi cantly reduce larval populations of several
main vectors shortly after their introduction to
the breeding site (see Table 3.1).
In some situations, it is possible to use a
combined intervention using larvivorous fi sh
with a suitable larvicide. For example, a fi eld
trial has been performed in
man-made canals in
Kisumu, western Kenya, using
G
.
ai nis
together
with the microbial larvicide
Bacillus thuringiensis
israelensis
(Bti), which has low toxicology for fi sh
(Imbahale
et al
., 2011). There was an overall
Malaria
A community-based initiative programme was
introduced in Somalia in 1987. The programme
was initially implemented in the Marka district
of the lower Shabelle region but gradually
expanded to cover a population of 189,466 in
13 districts in the three zones of Somalia. An
innovative approach implemented in Somalia
for the control of malaria was the introduction
of larvivorous fi sh in ponds, which reduced the
disease rates (WHO, 2012).
Larvivorous fi sh such as
Aplocheilus blocki
,
P
.
reticulata
and
G
.
ai nis
and biolarvicides
(
Bacillus sphaericus
H5a5b (B101) and
B
.
thuringiensis
var.
israelensis
H-14 strain 164)
were introduced to
Anopheles stephensi
larval
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