Water Management for Disease Vector Control - Biological and Environmental Control of Disease Vectors - page 165

breeds in the polluted waters of cesspits, ditches,
drains, water storage containers and elements
of solid waste. In such settings, water manage-
ment as an entry point for control may focus on
the management of waste water, which is
discussed in a previous chapter (see Ensink et al .,
Chapter 8, this volume).
Erlanger et al . (2005) reviewed the
literature on water resources development and
its impacts on lymphatic fi lariasis, and found
that mosquito densities of the An . gambiae
complex and An . funestus may be up to 25-fold
higher in irrigated areas when compared with
irrigation-free sites, and that the infection
prevalence of lymphatic fi lariasis often increased
after the implementation of a water resources
development project, though there was no clear
association with clinical symptoms. They
concluded that there is a need to assess and
quantify changes of transmission parameters,
and clinical manifestations over the entire
course of water resource developments.

of larvivorous fi sh as its main components could
reduce vector populations, and hence has the
potential to reduce the transmission level and
the burden of JE (Keiser et al ., 2005a).

9.2.4 Schistosomiasis

A systematic literature review and meta-analysis
examining a large number of published studies
from primarily African settings concluded that
the development and management of water
resources is an important risk factor for
schistosomiasis (Steinmann et al ., 2006).
Findings from across Africa have documented
the potential for schistosomiasis to be introduced,
and for the intensity of infection to increase,
following the development of irrigation and the
thousands of small dams that are being built in
Africa for agriculture, livestock and drinking
water supply. Likewise, intensity of human
infection and duration of transmission may be
impacted by such development. Schistosomiasis
was non-existent or sporadically reported from
Sudan before the establishment of the Gezira, or
Blue Nile, irrigation scheme. Similar reports
have come from other schemes within Sudan
and Egypt (FAO, 1987). Also, increases in
schistosomiasis have been recorded following
irrigation and dam development projects such as
the Volta Lake Project in Ghana, the Oyan
Reservoir in Nigeria and the Oi ce du Niger in
Mali (Hunter, 2003; Mafi ana et al ., 2003;
Coulibaly et al ., 2004).
Irrigation systems provide ample oppor-
tunities for human contact with water, either
occupationally while farming or washing of
laundry, or recreationally by playing in and
around irrigation or drainage canals. Especially
farmers and farm workers working within the
irrigation system may be in contact with infested
water for extended periods of time, generating
high intensities of infection. The absence of
household sanitation, or the preference for open
defecation, may result in human contamination
of snail-infested water through urine or faeces,
which support the continued transmission of
the schistosomiasis parasite in areas close to
water reservoirs or within irrigation systems. It
is likely that direct contamination occurs when
urinating in water, or when people use canal
water to wash after defecation. Water used for

9.2.3 Japanese encephalitis

Japanese encephalitis (JE) is a disease caused by
an arbovirus that is spread by marsh birds,
amplifi ed by pigs, and mainly transmitted by the
bite of infected Cx . tritaeniorhynchus , Cx . vishnui ,
Cx . fuscocephala and Cx . gelidus mosquitoes
(Hasegawa et al ., 2008). Restricted to India,
parts of China, Korea, Japan and the whole of
South-east Asia, JE is closely associated with
irrigated rice ecosystems, a favoured habitat for
the vector, and increased in areas in which pig
rearing is practised as a source of food and
income generation. Because of the critical role
of pigs, its presence in Muslim countries is
negligible. Vaccination initiatives are the
mainstay of controlling JE outbreaks, but water
management methods have been used to control
the mosquito vector, especially the alternate wet
and dry method of cultivating rice. Keiser et al .
(2005a) estimated from the published literature
that 1.9 billion people currently live in rural JE-
prone areas of the world. Among them, 220
million people live in proximity to rice-irrigation
schemes. It was concluded that in JE-endemic
rural settings, where vaccination rates are often
low, an integrated vector management approach
with alternate wet and dry irrigation and the use