Editorial: Dengue and solid waste management

DENGUE continues to spread, hospitals are still filled to the brims by dengue patients, and the rainy season is not halfway over yet.

Earlier, the City Government launched the "4 o'clock habit", which encourages residents to clean up their yards every afternoon as the first defense against dengue. That's a good start. But we all know that dengue mosquitoes still abound, the disease having already killed 57 in the city. There is something happening that we still do not have full grasp of.

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And thus we underscore a point raised by environmentalist Ipat G. Luna on the relationship of dengue and solid waste management, as she shared to social network friends a scientific study that can be accessed online that proved eggs of the Aedes aegypti (the mosquito carrier of dengue) long periods of quiescence where these are laid, and then hatch when it comes in contact with water.

The study, "Ovipositional behavior of Aedes aegypti (Diptera, Culicidae) in different strata and biological cycle" was published in 2003 as conducted by Ionizete Garcia Silva, Heloisa Helena Garcia da Silva, and Cleyverton Garcia Lima who bred the aegypti mosquitoes in the Laboratory of Biology and Physiology of Insects, in the Federal University of Goias in Brazil. The dengue carrying mosquitoes were bred in different mediums on the premise that "seaons that have dry and/or cold weather are not proper for development of Aedes aegypti" since the seasons would have naturally controlled the mosquitoes' population.

While it is now common knowledge that breeding grounds of mosquitoes are the damp places and stagnant water, what is not known to all but is a fact to those working with tropical diseases is that aegypti eggs can remain in quiescence (dormancy) for even two years if it is not in contact with water. And as the study above noted, the eggs are laid on the walls of the breeding devices used instead of on the water as we assumed.

Just to make the experiment even more interesting, the mosquitoes first indicated preference to lay in liquid surface as against those humid and rough. But after several laying, the mosquitoes preferred to lay eggs on the humid and rough sufaces than on the liquid.

This indicates that the mosquitoes are ensuring the continued reproduction of their species as the seasons progress. Egg laying would be best on water if water is prevalent and then in the humid and rough surfaces as the dry season comes in.

"This habit of the mosquito A. aegypti of laying eggs on the walls of the breeding device could mean a mechanism to increase dispersion and density," the study reads. Lay as many eggs in the water when the rains are here and then continue on laying on walls to await the next rainy season.

"This behavior is important to control this mosquito, and that is because the eggs attached to recipient walls resist to desiccation and hatch later when the level of water rises. There comes the importance of sending non-degradable trash, such as plastic, glass, rubber and others, to proper destiny," the study continues.

Learning from these, we now know that it's not enough to turn bottles, plastic containers, and tires upside down because the eggs will just be there, waiting for "when the level of water rises" or when the container is upturned. Beyond just turning these upside down is to ensure that these are properly disposed of.