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Kimpatsu Hekigan


Oct 31, 2015, 2:46 PM

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Cheap screens reduce dengue and chikungunya mosquitoes

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Study conducted in Merida and on the Yucatan Peninsula:

The use of long-lasting pesticide-treated nets as framed screening in houses in mosquito-infested areas of Mexico significantly reduced the presence of the insects and their larvae in homes, researchers reported here.


Cheap Screens Reduce Mosquitoes in Mexican Homes

FWIW,

-- K.H.


The Disciple lamented, "Master! Why is my life beset with problems?!"
The Master observed, "Only tourists step in dog droppings."





YucaLandia


Nov 1, 2015, 5:55 AM

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Re: [Kimpatsu Hekigan] Cheap screens reduce dengue and chikungunya mosquitoes

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Fun study.

Does it seem odd to anyone that the Merida researchers found that they needed insecticide**-treated screens to reduce mosquitoes to reduce mosquitoes by just 59% ?

Does it also seem odd that their proposed treatment/protection still allows many many Chikungunya & Dengue infected mosquitoes to live in Merida homes ? ...

Does it seem odd that the researchers did not mention Dengue or Chikungunya infection rates of the families living in their treated homes? .... The real goal is Dengue & Chikungunya reduction.

This means that their proposed insecticide-treated screening program did not reduce Chikungunya or Dengue cases in the tested homes - a key item missing from their last-minute report / study.

Some fewer mosquitoes is a good thing ... but no Dengue, no Chikungunya, (and no Zika virus) infections are the REAL goal.

This means choosing a system that allows NO mosquitoes into the home .... to offer real disease protection to people.

Dr. Pablo Manrique Saide & Dr. Mendez's study's 60% reduction ... means that 40% of mosquitoes are still in homes, infecting people.

=============================
Based on other past (2007) parallel studies and current parallel Aedes aegypti & Dengue studies in Merida:
The missing key is that these researchers did not cover the doorways.

If a family covers the doorways with good mosquito-proof nylon curtains, the mosquitoes cannot enter a well-screened house - and the insecticide is not needed.

A second key to lowering Dengue and Chikungunya risks is the type of insecticide used on the screen.

Adding insecticide** sometimes poisons the mosquitoes as they land on the screens, trying to enter the home or leave the home. This occasional poisoning of mosquitos leaving the home to find breeding sites (lay eggs) and occasional poisoning of mosquitoes entering the home to find blood meals ... sometimes reduces the numbers of mosquitoes around and in the house.

Science Talk:
The formal scientific term for the ability of an insecticide-treated material to reduce mosquitoes is called "Knock Down Resistance" (KDR). Since the PRI came to power in Merida: Merida's government has haphazardly and ineffectively used permethrin public spraying in the past to try to reduce the Aedes aegypti mosquitoes that carry Chikungunya & Dengue viruses. These past Merida mostly-ineffective insecticide sprayings have made most Merida mosquitoes resistant to many of the permethrin insecticides.

**This significant key to using insecticide-treated materials requires that the mosquitoes not be resistant to that specific insecticide => the insecticide must have a very low KDR .. and last for years ... to work.

Note that the researchers do not mention KDR rates. ... nor do they mention the degradation rates of their insecticide.

This means that the permethrin-treated window coverings that previously worked in Merida ... now ... don't work in Merida due to high KDRs due to increasing permethrin insecticide-resistance from past years of ineffective PRI govt. spraying programs.

These researchers chose an insecticide version (alpha-cypermethrin) that the Merida government only recently started to use - because the govt. found their other permithrin formulations stopped working. By changing insecticides, it means it's only a matter of time (a year or less?) until these researcher's alpha-cypermethrin treated materials will likely no longer work due to the mosquitoes evolving almost guaranteed resistance to alpha-cypermethrin.


The other major missing issue with this study:
A well screened home ~ with GOOD good door coverings ~ does not need insecticide treated screens - because screens + door curtains => stop mosquito movement.

A big past Merida study on this exact topic showed that in both screened homes and in homes with insecticide-treated window curtains .... the mosquitoes enter through the doorways ... especially as many Meridadanos leave their doors open for periods long enough for mosquitoes to enter ... and because the Aedes aegypti mosquitoes also love to fly close to the (smelly) backs of our clothing ... drafting in with us as we enter through even a closed door.

Having a door curtain that drapes over your back as you enter the door, stops this significant mode of mosquitoes entering our homes. We've found that a system of 2 specially installed door curtains + ordinary well-maintained screens can provide up to a month of NO mosquitoes in the house.

So, the real long-term effectiveness keys to stopping Dengue & Chikungunya (and Zika) carrying Aedes aegypti mosquitoes are:
~ good screens
~ screens that are properly installed (no gaps - or gaps plugged with screening material)
and
~ good door curtains

plus
~ As Yellow Fever control-efforts a century ago proved: We must also eliminate mosquito breeding sites in and around our homes and communities ~ to provide community-wide protection.

Happy Trails,
Doctor Yucalandia


because the Aedes aegypti mosquitoes are excellent flyers and have long-proven abilities to quickly become resistant to

Overall: This means that good well-maintained screens + a good door curtain = enough protection to exclude ALL mosquitoes from our Merida homes.
-
Read-on MacDuff
E-visit at http://yucalandia.com

(This post was edited by YucaLandia on Nov 1, 2015, 6:26 AM)
 
 
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