Use of Larvivorous Fish in Biological and Environmental Control of Disease Vectors - Biological and Environmental Control of Disease Vectors - page 30

habitats in Panaji (Goa) during 1990. Malaria
surveillance and case treatment were improved.
Health education campaigns were organized,
including help of private doctors and the Indian
Medical Association. These bioenvironmental
interventions led to control of malaria trans-
mission in Panaji (Goa) and decline in malaria
incidence up to 88.5% by 1992 (MRC India,
2012).
The National Vector Borne Disease Control
Programme (NVBDCP) along with assistance
from the World Bank launched the 'Enhanced
Malaria Control Project' (EMCP) in 1997. From
1997 to 2004, more than 300,000 village-
based volunteers were trained in malaria case
management and employed in EMCP districts in
India. More than 20,000 larvivorous fi sh
hatcheries were established, while at the same
time the population covered by indoor residual
spraying decreased by almost 50% in EMCP
districts (Barat, 2006). Consequently, malaria
morbidity decreased by 38% nationwide and by
43% in EMCP districts. In three states, Gujarat,
Andhra Pradesh and Maharashtra, malaria
morbidity was reduced by 65-70%.
In 1993, one highly malaria-prone area,
Kamasamudram (Primary Health Centre (PHC),
population over 37,000) in Karnataka, India
was selected for a malaria control intervention
by Ghosh, S.K. et al . (2005). Wells, ponds and
streams were the main breeding habitats of the
two vector species An . culicifacies (species A and
B) and An . fl uviatilis and it was found that
malaria was comparatively numerous in six sub-
centres of this PHC. Those villages with higher
numbers of malaria cases were surrounded by
wells and ponds. Species A of An . culicifacies was
more numerous in villages with wells and ponds,
whereas species B was more abundant in villages
located near streams. Species A is an ei cient
carrier of malaria parasites, while species B
exhibits partial refractoriness to Plasmodium
falciparum and complete refractoriness to
Plasmodium vivax infections (Adak et al ., 2006).
All An . fl uviatilis belonged to species T, which are
zoophagic and therefore not a vector of human
malaria (Ghosh, S.K. et al ., 2005). This
information helped in designing the larval
source management of the vector species. The
plan for channelization of the streams, which
was associated with a huge cost, was not taken

up. Subsequent surveys in the non-malarious
sub-centres detected the presence of Poecilia fi sh
in most of the breeding habitats and an
associated absence of the mosquito vector
species. Poecilia was therefore introduced in all
the breeding habitats, especially in ponds and
wells in 1994. This resulted in almost 50%
reduction of malaria incidence in 1995 from an
average annual parasite index (API; cases per
1000 population per year) of over 40. However,
Poecilia proved to be inef ective in reducing
mosquito numbers in ponds. In late 1995,
approximately 500 Gambusia were released in a
ditch connected with the main channel of
Kamasamudram tank. In 1996, a heavy fl ood
dispersed those Gambusia fi sh throughout the
entire area. Subsequently, this resulted in total
elimination of malaria in this area for over 15
years. The very low levels of vector abundance
that were sustained did not support malaria
transmission. In 2001, the trial was extended to
a highly malaria-endemic area with average API
of over 130, and malaria reached near
elimination phase (Ghosh et al ., 2012).
Self-maintaining populations of Gambusia
in village ponds and Poecilia in wells virtually
eliminated malaria in study villages in the south
Indian state of Karnataka. This method of
control was initiated due to the reluctance of silk
growers to allow insecticidal spraying because
of the danger to silkworms (Ghosh, S.K. et al .,
2005). In Kolar district (population 36,484; 93
villages), only two malaria cases were reported
in 2005 compared with 1446 cases in 1993.
Similarly, in another four districts (population
1.2 million; 1766 villages), 497 cases were
reported in 2005 compared with 73,270 cases
in 2001 (Ghosh, S.K. et al ., 2006a). The results
have been so remarkable that the use of fi sh in
vector control has been extended to many other
areas of the Indian state (Ghosh and Dash,
2007).
Larvivorous fi sh ( Gambusia spp.) were
introduced by Singh et al . (2006) into large and
small ponds that were identifi ed as breeding
places of vectors in some tribal villages of Betul
district, Madhya Pradesh, India along with
application of two rounds of IRS with synthetic
pyrethroids. Pre-intervention surveys revealed a
very high fever rate in the tribal community in
all age groups with a slide positivity rate of more