we know that DEC is given as part of the national filaria programme every year. (MDA statergy). why is it given once in a year and why not once in six months or once in 2 months or so?

maybe its because we cant afford to run the whole exercise for more than once a year.the idea is to give the drug to ALL people at the same time...and ensuring they take it...so it must be hard enough doing it once a year.

it is partly correct. if the strategy of MDA once a year is not effective, then it would be a waste of resources even if ALL are covered.
the answer is partly correct
"once we give MDA the filarial load decreases and it takes one year for the filarial load to come back to the normal level and this is when we one more shot and also it is cost effective"

HI

Just to add to what Maha has said......

All these guidelines with respect to frequency and duration of MDA is based on Statistical Modelling studies conducted which try to predict what can happen given certain conditions.
The idea of 80% consumption atleast once a year for about 6-8 years(fecundic life span of adult worm) will lead to such a low community microfilarial load that culex mosquitoes cannot pick up microfilaria from the human beings and hence transmission is permanently interrupted - which will lead to Elimination of Lymphatic Filariasis.

The targets of RNTCP are to achieve atleast 85% cure rate and 70% case detection rate among New smear positive cases. Ever tried to think what is so special about 85 and 70%?? they are again based on Modelling studies.

it's really good