We have 'long lasting net' product category supported by WHO which is defined as such by WHO critera for washfastness, i.e. the nets knockdown at least 95% and/or kill at least 80% of the mosquitoes after 20 'standard' washes.
What should the criteria be for a long lasting IRS product? 6 months residual; at least 6 months; 1 year's residual?? And why?
What is the definition of long lasting IRS?
June 21, 2010 - 09:17
#1
What is the definition of long lasting IRS?
September 1, 2010 - 08:54
#2
Hi Mark, I would argue that
Hi Mark, I would argue that long lasting IRS should last for 2 seasons. So in most cases 18months residual effect. That would allow to cut a spray cycle and, in many cases, treat every other year. I would argue that the operational perspective needs be factored into a such claim. With a long lasting IRS we aim to provide for substantial cost reduction by cut in the most significant cost contributor; application.
So 18months and you qualify for LLIRS.
November 5, 2010 - 06:48
#3
Longlasting IRS
How long will the treated net have a residual content of insecticide sufficient to kill vectors - is akin to asking 'how is a piece of string'
The residual effect will vary dependent on a number of factors :-
In Africa, ie:- during the rainy season (malaria season) cooking will often be done indoors - using wood fires - using cooking oil. In the same room where the ITN hangs.
First: the smoke from the fire will permiate the net and mask the chemicals.
Second; the cooking oil will vaporize and cloak the net with a sticky mist, thus destroying the residual effect - although some mosquitoes may be trapped by the sticky cooking oil residue.
Therefore, there may be a good reason to wash the net with a strong detergent and retreat it with an appropriate vector insecticide at intervals during the malaria season.
March 18, 2011 - 12:49
#4
response in regards to dirty nets
Dear Richard,
Even if this thread is about IRS and not LLIN, I would still like to address your post.
Generally, do not advice the use of "strong detergents". If your "strong detergent" does indeed work as a solvent (as suggested) for the pyrethroids the net in question, you likely will ruin the net chemically. Since that in most areas where LLIN have been distributed there will likely not be any follow up with retreatment kits, this is surely ill advice.
Instead, use the standard detergents as prescribed by (all) the manufacturers.
In regards to whether the grease and dirt will mask the effect of the pyrethroids, I believe is no closed case. I think most people with these nets simply wash and scrub them because they look disgusting.
If you are planning to distribute nets to areas where they are likely to be used rooms doubling as kitchens, you may want to consider a few things.
Is white the right color? Nets will look dirty faster and may be scrubbed harder or invite for harsher detergents.
Note that certain type of fabrics collect dirt faster and are harder to clean than others by virtue of their characteristics. Polyester nets are made from of multi-strand texturized yarns, which means the surface of the yarn is ripped up to give it a soft, fabric like feeling.Polyethylene yarns are made of a single, smooth fiber, which gives them a more stiff plastic like feeling. This means that polyester nets will pick up grease and dirt much faster and is also much harder to clean than the polyethylene net. It is more or less like trying to clean a fabric bag (like cotton bags) vs a plastic bag.
Choose a design of net that can be put up and taken away at no convenience to the user. The reason why net users leave their nets hanging close to the kitchen stove may be that is too much of a hassle to take them up and down. New net designs address this very issue specifically.
In regards to IRS, I still define long lasting as 18months.
All the best,