Final Report on Mosquito Breeding Research - SNV

1. Introduction
A wide range of tropical diseases are spread by biting insects, the most dangerous being malaria.
Since, mosquitoes tap into the blood of birds, animals and humans; they can be ghoulishly efficient at
transmitting certain diseases. While some mosquito-borne diseases can be deadly to humans, many
cause only minor, passing symptoms in most people. Malaria is considered to be a major
international public health problem, causing 300-500 million infections worldwide and
approximately one million deaths annually, according to the Centers for Disease Control and
Prevention (CDC) 1 . Since, Mosquitoes carry many different kinds of diseases including malaria,
heartworm, dengue fever, encephalitis and yellow fever. Complains regarding, increase of
mosquito breeding in the outlet tank of biogas plants certainly will rupture the image of Biogas
technology.
In study carried out by IEIA during the first months of 2002, contained over 50 positive points; apart
from one striking negative points mentioning the increase of mosquitoes in the kitchen of the house
holds with biogas plant. Incident of mosquito increase in some 70% of plant, out of 600 plants that
they surveyed, have been reported. The most likely cause, that we perceive in regard to increase in
mosquito is because, the houses using biogas for cooking produced no smoke in comparison to that
of houses using traditional fuel wood. Though the Smoke free indoor environment has provided
numerous health benefits to households it has also provided a pleasant environment for mosquitoes as
well. As we recall the past, we come to know that smoke was used as insect repellent before man
made chemical repellent invaded our society. Thus the smoke free indoor environment is the main
cause of increase of mosquito inside the house of biogas users. Such cases therefore can be assumed
in about 1, 34,000 household having biogas throughout Nepal.
The second most likely cause is due to improper feeding practices such as difference in mixing
proportion, excessive amount of water entering biogas digester through attached toilet and so on.
The nitrogen content of the slurry also discourages mosquito breeding when they are at the
specific range. Excessive water content in the mixture will dilute nitrogen levels that otherwise
would be high enough to retard mosquito breeding. High nitrogen values alone will
1 Centers for Disease Control and Prevention report - 2003.
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